1
|
Ahn CH, Yang WS, Kim JJ, Kim JH, Cho HK. Design of Bronze-Rich Dual-Phasic TiO 2 Embedded Amorphous Carbon Nanocomposites Derived from Ti-Metal-Organic Frameworks for Improved Lithium-Ion Storage. Small Methods 2022; 6:e2201066. [PMID: 36126169 DOI: 10.1002/smtd.202201066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Indexed: 06/15/2023]
Abstract
Dual-phasic (DP)-TiO2 -based composites are considered attractive anode materials for high lithium-ion storage because of the synergetic contribution from dual-phases in lithium-ion storage. However, a comprehensive investigation on more efficient architectures and platforms is necessary to develop lithium-storage devices with high-rate capability and long-term stability. Herein, for the first time, a rationally designed bronze-rich DP-TiO2 -embedded amorphous carbon nanoarchitecture, denoted as DP-TiO2 @C, from sacrificial Ti-metal-organic frameworks (Ti-MOFs) via a two-step pyrolysis process is proposed. The bronze/anatase DP-TiO2 @C nanocomposites are successfully synthesized using a unique pyrolysis process, which decomposes individually the metal clusters and organic linkers of Ti-MOFs. DP-TiO2 @C exhibits a significantly high density and even distribution of nanoparticles (<5 nm), enabling the formation of numerous heterointerfaces. Remarkably, the bronze-rich DP-TiO2 @C shows high specific capacities of 638 and 194 mAh g-1 at current densities of 0.1 and 5 A g-1 , respectively, owing to the contribution of the synergetic interfacial structure. In addition, reversible specific capacities are observed at a high rate (5 A g-1 ) during 6000 cycles. Thus, this study presents a new approach for the synthesis of DP-TiO2 @C nanocomposites from a sacrificial Ti-MOF and provides insights into the efficient control of the volume ratio in DP-TiO2 anode architecture.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Won Seok Yang
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Jeong Jae Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Jae Hyun Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Division of Energy Technology, Daegu Gyeongbuk Institute of Science & Technology, Daegu, 42988, Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| |
Collapse
|
2
|
Deshpande NG, Kim DS, Ahn CH, Jung SH, Kim YB, Lee HS, Cho HK. β-like FeOOH Nanoswords Activated by Ni Foam and Encapsulated by rGO toward High Current Densities, Durability, and Efficient Oxygen Evolution. ACS Appl Mater Interfaces 2021; 13:18772-18783. [PMID: 33856769 DOI: 10.1021/acsami.1c01428] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
As an alternative to the oxygen evolution reaction (OER) electrocatalyst developed by a complex bi- or multimetal ion with layered double hydroxide (LDH) structures, we design a simple, self-supported, and single-metal-ion OER electrocatalyst having lower overpotentials and high current densities in alkaline water electrolyzers. Here, β-like FeOOH nanosword structures encapsulated by reduced graphene oxide (rGO) were cost-effectively synthesized on formable Ni foam substrates as an efficient and highly durable OER catalyst. It is revealed that the rGO uniformly covered the β-like FeOOH nanoswords to form a porous network achieving a lower overpotential of only 210 mV at 10 mA cm-2 with a stable operation for more than 40 h in alkali media. Moreover, a high current density of ∼300 mA cm-2 was achieved at less than 1.8 V. In-depth physical and electrochemical analysis indicated that the intrinsic charge transfer through activated Ni-foam, β-like phase, and nanosword morphology was evidently beneficial for enhancing the OER activity of the bare FeOOH, and its encapsulation by rGO further improved the conductivity and long-life durability. Our integrated OER electrocatalyst developed by a simple method (repeated soaking and quenching process) will aid in scaling up β-like FeOOH nanoswords for preparing uniform and large-area electrodes for industrial purposes.
Collapse
Affiliation(s)
- Nishad G Deshpande
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Dong Su Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Sung Hyeon Jung
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Young Been Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Ho Seong Lee
- School of Materials Science and Engineering, Kyungpook National University, 80 Daehakro, Buk-gu, Daegu 41566, Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University (SKKU), 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| |
Collapse
|
3
|
Ahn CH, Deshpande NG, Lee HS, Cho HK. Energy Transfer-Induced Photoelectrochemical Improvement from Porous Zeolitic Imidazolate Framework-Decorated BiVO 4 Photoelectrodes. Small Methods 2021; 5:e2000753. [PMID: 34927880 DOI: 10.1002/smtd.202000753] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 10/08/2020] [Indexed: 06/14/2023]
Abstract
BiVO4 , which is a representative photoanode material for photoelectrochemical water splitting, intrinsically restricts high conversion efficiency, owing to faster recombination, low electron mobility, and short electron diffusion length. While the photocurrent density of typical BiVO4 corresponds to only 21.3% of the maximum photocurrent density (4.68 mA cm-2 ), decoration of the BiVO4 photoanode with zeolitic imidazolate framework-67 (ZIF-67) exhibits a synergetic effect to raise the overall photocatalytic ability at the BiVO4 surface region to a higher level via the energy-transfer process from BiVO4 to ZIF-67. The hybrid ZIF-67/BiVO4 photoanode follows two convenient photoelectrochemical pathways: 1) energy-transfer-induced water oxidation reaction in ZIF-67 and 2) water oxidation reaction by direct contact between the BiVO4 surface and electrolytes. Compared to the moderate photocurrent density (≈1 mA cm-2 ) of single-layer BiVO4 , the proposed ZIF-67/BiVO4 photoanodes show a remarkably high photocurrent (2.25 mA cm-2 ) with high stability, despite the lack of hole scavengers in the electrolyte. Furthermore, the absorbed photon-to-current efficiency of the ZIF-67/BiVO4 photoanode is ≈2.5 times greater than that of BiVO4 . This work proposes a promising solution for efficient water oxidation that overcomes the intrinsic material limitations of BiVO4 photoelectrodes by using energy transfer-induced photon recycling and the decoration of porous ZIFs.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Nishad G Deshpande
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Ho Seong Lee
- School of Materials Science and Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu, 41566, Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
- Research Center for Advanced Materials Technology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| |
Collapse
|
4
|
Deshpande NG, Ahn CH, Kim DS, Jung SH, Kim YB, Cho HK. Bifunctional reusable Co0.5Ni0.5Fe2O4 nanoparticle-grafted carbon nanotubes for aqueous dye removal from contaminated water. Catal Sci Technol 2020. [DOI: 10.1039/d0cy01057j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Highly stable and reusable CNF-grafted CNTs for efficient and effective aqueous dye removal from contaminated waters.
Collapse
Affiliation(s)
- Nishad G. Deshpande
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Dong Su Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Sung Hyeon Jung
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Young Been Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| |
Collapse
|
5
|
Park Y, Kang B, Ahn CH, Cho HK, Kwon H, Park S, Kwon J, Choi M, Lee C, Kim K. Bionanoelectronic platform with a lipid bilayer/CVD-grown MoS2 hybrid. Biosens Bioelectron 2019; 142:111512. [DOI: 10.1016/j.bios.2019.111512] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 06/20/2019] [Accepted: 07/12/2019] [Indexed: 12/21/2022]
|
6
|
Lee JH, Yoo YM, Jung EM, Ahn CH, Jeung EB. Inhibitory effect of octyl-phenol and bisphenol A on calcium signaling in cardiomyocyte differentiation of mouse embryonic stem cells. J Physiol Pharmacol 2019; 70. [PMID: 31566189 DOI: 10.26402/jpp.2019.3.10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 06/28/2019] [Indexed: 11/03/2022]
Abstract
Endocrine-disrupting chemicals (EDCs) have structures similar to steroid hormones and can interfere with hormone synthesis and normal physiological functions of reproductive organs. For example, sex steroid hormones influence calcium signaling of the cardiac muscle in early embryo development. To confirm the effect of progesterone (P4), octyl-phenol (OP), and bisphenol A (BPA) on early differentiation of mouse embryonic stem cells (mESCs) into cardiomyocytes, mESCs were treated with P4, OP, and BPA two days after attachment and media were replaced every two days. In addition, cells were treated with mifepristone (RU486), a synthetic steroid that has an affinity for progesterone receptor (Pgr), for one day starting on day 11. Beating ratio was decreased with P4, OP, and BPA treatment. The Pgr mRNA level was significantly increased in the P4-, OP- and BPA-treated groups. However, the mRNA level of the calcium channel gene (Trpv2), contraction-related genes (Ryr2, Cam2, and Mylk3) and cardiac development and morphogenesis genes (Rbp4, Ly6e, and Gata4) were significantly decreased in the P4-, OP-, and BPA-treated groups. Interestingly, treatment with RU486 rescued the altered calcium channel gene, contraction-related genes, and cardiac development and morphogenesis genes. P4, OP, and BPA treatments reduced the intracellular calcium level. Taken together, these results indicate that EDCs (OP and BPA) has a structure similar to that of endogenous steroid hormones such as progesterone and estrogen, and OP and BPA act like progesterone to inhibit and disrupt cardiomyocyte differentiation of mESCs.
Collapse
Affiliation(s)
- J-H Lee
- Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea
| | - Y-M Yoo
- Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea
| | - E-M Jung
- Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea
| | - C H Ahn
- Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea
| | - E-B Jeung
- Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea.
| |
Collapse
|
7
|
Lee CM, Jin CH, Ahn CH, Cho HK, Lim JH, Hwang SM, Joo J. Enhanced Gas Sensing Performance of Hydrothermal MoS2 Nanosheets by Post-Annealing in Hydrogen Ambient. BCSJ 2019. [DOI: 10.1246/bcsj.20190004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Chang Min Lee
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 16419
| | - Chan Ho Jin
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 16419
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 16419
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 16419
| | - Jun Hyung Lim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 16419
| | - Soo Min Hwang
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Korea 16419
| | - Jinho Joo
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 16419
| |
Collapse
|
8
|
Rodriguez J, Chandorkar SA, Watson CA, Glaze GM, Ahn CH, Ng EJ, Yang Y, Kenny TW. Direct Detection of Akhiezer Damping in a Silicon MEMS Resonator. Sci Rep 2019; 9:2244. [PMID: 30783192 PMCID: PMC6381092 DOI: 10.1038/s41598-019-38847-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 12/11/2018] [Indexed: 11/13/2022] Open
Abstract
Silicon Microelectromechanical Systems (MEMS) resonators have broad commercial applications for timing and inertial sensing. However, the performance of MEMS resonators is constrained by dissipation mechanisms, some of which are easily detected and well-understood, but some of which have never been directly observed. In this work, we present measurements of the quality factor, Q, for a family of single crystal silicon Lamé-mode resonators as a function of temperature, from 80–300 K. By comparing these Q measurements on resonators with variations in design, dimensions, and anchors, we have been able to show that gas damping, thermoelastic dissipation, and anchor damping are not significant dissipation mechanisms for these resonators. The measured f · Q product for these devices approaches 2 × 1013, which is consistent with the expected range for Akhiezer damping, and the dependence of Q on temperature and geometry is consistent with expectations for Akhiezer damping. These results thus provide the first clear, direct detection of Akhiezer dissipation in a MEMS resonator, which is widely considered to be the ultimate limit to Q in silicon MEMS devices.
Collapse
Affiliation(s)
- Janna Rodriguez
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA.
| | - Saurabh A Chandorkar
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA
| | - Christopher A Watson
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California, 94025, USA
| | - Grant M Glaze
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA
| | - C H Ahn
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA
| | - Eldwin J Ng
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA
| | - Yushi Yang
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA
| | - Thomas W Kenny
- Department of Mechanical Engineering, Stanford University, Stanford, California, 95304, USA
| |
Collapse
|
9
|
Kim KS, Ahn CH, Jung SH, Cho SW, Cho HK. Toward Adequate Operation of Amorphous Oxide Thin-Film Transistors for Low-Concentration Gas Detection. ACS Appl Mater Interfaces 2018; 10:10185-10193. [PMID: 29493206 DOI: 10.1021/acsami.7b18657] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We suggest the use of a thin-film transistor (TFT) composed of amorphous InGaZnO (a-IGZO) as a channel and a sensing layer for low-concentration NO2 gas detection. Although amorphous oxide layers have a restricted surface area when reacting with NO2 gas, such TFT sensors have incomparable advantages in the aspects of electrical stability, large-scale uniformity, and the possibility of miniaturization. The a-IGZO thin films do not possess typical reactive sites and grain boundaries, so that the variation in drain current of the TFTs strictly originates from oxidation reaction between channel surface and NO2 gas. Especially, the sensing data obtained from the variation rate of drain current makes it possible to monitor efficiently and quickly the variation of the NO2 concentration. Interestingly, we found that enhancement-mode TFT (EM-TFT) allows discrimination of the drain current variation rate at NO2 concentrations ≤10 ppm, whereas a depletion-mode TFT is adequate for discriminating NO2 concentrations ≥10 ppm. This discrepancy is attributed to the ratio of charge carriers contributing to gas capture with respect to total carriers. This capacity for the excellent detection of low-concentration NO2 gas can be realized through (i) three-terminal TFT gas sensors using amorphous oxide, (ii) measurement of the drain current variation rate for high selectivity, and (iii) an EM mode driven by tuning the electrical conductivity of channel layers.
Collapse
Affiliation(s)
- Kyung Su Kim
- School of Advanced Materials Science and Engineering , Sungkyunkwan University , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 16419 , Republic of Korea
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering , Sungkyunkwan University , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 16419 , Republic of Korea
| | - Sung Hyeon Jung
- School of Advanced Materials Science and Engineering , Sungkyunkwan University , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 16419 , Republic of Korea
| | - Sung Woon Cho
- School of Advanced Materials Science and Engineering , Sungkyunkwan University , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 16419 , Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering , Sungkyunkwan University , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 16419 , Republic of Korea
| |
Collapse
|
10
|
Kim KS, Ahn CH, Kang WJ, Cho SW, Jung SH, Yoon DH, Cho HK. An All Oxide-Based Imperceptible Thin-Film Transistor with Humidity Sensing Properties. Materials (Basel) 2017; 10:ma10050530. [PMID: 28772888 PMCID: PMC5458990 DOI: 10.3390/ma10050530] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 05/07/2017] [Accepted: 05/10/2017] [Indexed: 11/29/2022]
Abstract
We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O2 = 29:0.3 exhibited good electrical performances with Vth of −0.23 V, SS of 0.34 V/dec, µFE of 7.86 cm2/V∙s, on/off ratio of 8.8 × 107, and has no degradation for bending stress up to a 3.5-mm curvature. The imperceptible oxide TFT sensors showed the highest sensitivity for the low and wide gate bias of −1~2 V under a wide range of relative humidity (40–90%) at drain voltage 1 V, resulting in low power consumption by the sensors. Exposure to water vapor led to a negative shift in the threshold voltage (or current enhancement), and an increase in relative humidity induced continuous threshold voltage shift. In particular, compared to conventional resistor-type sensors, the imperceptible oxide TFT sensors exhibited extremely high sensitivity from a current amplification of >103.
Collapse
Affiliation(s)
- Kyung Su Kim
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| | - Cheol Hyoun Ahn
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| | - Won Jun Kang
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| | - Sung Woon Cho
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| | - Sung Hyeon Jung
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| | - Dae Ho Yoon
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| | - Hyung Koun Cho
- Department of Advanced Materials Science and Engineering, SungKyunKwan University, 2006 Seobu-ro, Jangan-gu, Gyeonggi-do, Suwon 16419, Korea.
| |
Collapse
|
11
|
Fabbris G, Meyers D, Okamoto J, Pelliciari J, Disa AS, Huang Y, Chen ZY, Wu WB, Chen CT, Ismail-Beigi S, Ahn CH, Walker FJ, Huang DJ, Schmitt T, Dean MPM. Orbital Engineering in Nickelate Heterostructures Driven by Anisotropic Oxygen Hybridization rather than Orbital Energy Levels. Phys Rev Lett 2016; 117:147401. [PMID: 27740843 DOI: 10.1103/physrevlett.117.147401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 06/06/2023]
Abstract
Resonant inelastic x-ray scattering is used to investigate the electronic origin of orbital polarization in nickelate heterostructures taking LaTiO_{3}-LaNiO_{3}-3×(LaAlO_{3}), a system with exceptionally large polarization, as a model system. We find that heterostructuring generates only minor changes in the Ni 3d orbital energy levels, contradicting the often-invoked picture in which changes in orbital energy levels generate orbital polarization. Instead, O K-edge x-ray absorption spectroscopy demonstrates that orbital polarization is caused by an anisotropic reconstruction of the oxygen ligand hole states. This provides an explanation for the limited success of theoretical predictions based on tuning orbital energy levels and implies that future theories should focus on anisotropic hybridization as the most effective means to drive large changes in electronic structure and realize novel emergent phenomena.
Collapse
Affiliation(s)
- G Fabbris
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - D Meyers
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - J Okamoto
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - J Pelliciari
- Research Department "Synchrotron Radiation and Nanotechnology", Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - A S Disa
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Y Huang
- Research Department "Synchrotron Radiation and Nanotechnology", Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - Z-Y Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - W B Wu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - C T Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - S Ismail-Beigi
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA
| | - C H Ahn
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA
| | - F J Walker
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - D J Huang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - T Schmitt
- Research Department "Synchrotron Radiation and Nanotechnology", Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| |
Collapse
|
12
|
Ahn CH, Kang WJ, Kim YK, Yun MG, Cho HK. Highly Repeatable and Recoverable Phototransistors Based on Multifunctional Channels of Photoactive CdS, Fast Charge Transporting ZnO, and Chemically Durable Al2O3 Layers. ACS Appl Mater Interfaces 2016; 8:15518-15523. [PMID: 27259048 DOI: 10.1021/acsami.6b04482] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Highly repeatable and recoverable phototransistors were explored using a "multifunctional channels" structure with multistacked chalcogenide and oxide semiconductors. These devices were made of (i) photoactive CdS (with a visible band gap), (ii) fast charge transporting ZnO (with a high field-effect mobility), and (iii) a protection layer of Al2O3 (with high chemical durability). The CdS TFT without the Al2O3 protection layer did not show a transfer curve due to the chemical damage that occurred on the ZnO layer during the chemical bath deposition (CBD) process used for CdS deposition. Alternatively, compared to CdS phototransistors with long recovery time and high hysteresis (ΔVth = 19.5 V), our "multi-functional channels" phototransistors showed an extremely low hysteresis loop (ΔVth = 0.5V) and superior photosensitivity with repeatable high photoresponsivity (52.9 A/W at 400 nm). These improvements are likely caused by the physical isolation of the sensing region and charge transport region by the insertion of the ultrathin Al2O3 layer. This approach successfully addresses some of the existing problems in CdS phototransistors, such as the high gate-interface trap site density and high absorption of molecular oxygen, which originate from the polycrystalline CdS.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Won Jun Kang
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Ye Kyun Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Myeong Gu Yun
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| |
Collapse
|
13
|
Kim YK, Ahn CH, Yun MG, Cho SW, Kang WJ, Cho HK. Periodically pulsed wet annealing approach for low-temperature processable amorphous InGaZnO thin film transistors with high electrical performance and ultrathin thickness. Sci Rep 2016; 6:26287. [PMID: 27198067 PMCID: PMC4873798 DOI: 10.1038/srep26287] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 04/27/2016] [Indexed: 11/09/2022] Open
Abstract
In this paper, a simple and controllable “wet pulse annealing” technique for the fabrication of flexible amorphous InGaZnO thin film transistors (a-IGZO TFTs) processed at low temperature (150 °C) by using scalable vacuum deposition is proposed. This method entailed the quick injection of water vapor for 0.1 s and purge treatment in dry ambient in one cycle; the supply content of water vapor was simply controlled by the number of pulse repetitions. The electrical transport characteristics revealed a remarkable performance of the a-IGZO TFTs prepared at the maximum process temperature of 150 °C (field-effect mobility of 13.3 cm2 V−1 s−1; Ion/Ioff ratio ≈ 108; reduced I-V hysteresis), comparable to that of a-IGZO TFTs annealed at 350 °C in dry ambient. Upon analysis of the angle-resolved x-ray photoelectron spectroscopy, the good performance was attributed to the effective suppression of the formation of hydroxide and oxygen-related defects. Finally, by using the wet pulse annealing process, we fabricated, on a plastic substrate, an ultrathin flexible a-IGZO TFT with good electrical and bending performances.
Collapse
Affiliation(s)
- Ye Kyun Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Myeong Gu Yun
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Sung Woon Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Won Jun Kang
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| |
Collapse
|
14
|
Kumah DP, Dogan M, Ngai JH, Qiu D, Zhang Z, Su D, Specht ED, Ismail-Beigi S, Ahn CH, Walker FJ. Engineered Unique Elastic Modes at a BaTiO_{3}/(2×1)-Ge(001) Interface. Phys Rev Lett 2016; 116:106101. [PMID: 27015492 DOI: 10.1103/physrevlett.116.106101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Indexed: 06/05/2023]
Abstract
The strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO_{3} where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO_{3}. While the complex crystal structure is predicted using first-principles theory, it is further shown that the details of the structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO_{3} induced by the symmetry of forces exerted by the germanium substrate.
Collapse
Affiliation(s)
- D P Kumah
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| | - M Dogan
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| | - J H Ngai
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| | - D Qiu
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| | - Z Zhang
- Argonne National Laboratory, Advanced Photon Source, Argonne, Illinois 60439, USA
| | - D Su
- Brookhaven National Laboratory, Center for Functional Nanomaterials, Upton, New York 11973, USA
| | - E D Specht
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - S Ismail-Beigi
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| | - C H Ahn
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| | - F J Walker
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA
| |
Collapse
|
15
|
Kang WJ, Ahn CH, Yun MG, Cho SW, Kim YK, Kim DE, Kim B, Cho HK, Kim Y. Expedient floating process for ultra-thin InGaZnO thin-film-transistors and their high bending performance. RSC Adv 2016. [DOI: 10.1039/c6ra06372a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Polyvinyl alcohol with low molecular weight exhibited good surface morphology and quick floating time for the fabrication of the top-gate oxide TFTs.
Collapse
Affiliation(s)
- Won Jun Kang
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Myeong Gu Yun
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Sung Woon Cho
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Ye Kyun Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Da Eun Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Bora Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Yunseok Kim
- School of Advanced Materials Science and Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| |
Collapse
|
16
|
Abstract
We review recent advances in our understanding of interfacial phenomena that emerge when dissimilar materials are brought together at atomically sharp and coherent interfaces. In particular, we focus on phenomena that are intrinsic to the interface and review recent work carried out on perovskite manganites interfaces, a class of complex oxides whose rich electronic properties have proven to be a useful playground for the discovery and prediction of novel phenomena.
Collapse
Affiliation(s)
- C A F Vaz
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | | | | | | |
Collapse
|
17
|
Yun MG, Ahn CH, Cho SW, Kim SH, Kim YK, Cho HK. Dual electrical behavior of multivalent metal cation-based oxide and its application to thin-film transistors with high mobility and excellent photobias stability. ACS Appl Mater Interfaces 2015; 7:6118-6124. [PMID: 25714371 DOI: 10.1021/am5085836] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effect of multivalent metal cations, including vanadium(V) and tin (Sn), on the electrical properties of vanadium-doped zinc tin oxide (VZTO) was investigated in the context of the fabrication of thin-film transistors (TFTs) using a single VZTO film and VZTO/ZTO bilayer as channel layers. The single VZTO TFT did not show any response to the gate voltage (insulator-like behavior). On the other hand, the VZTO/ZTO bilayer TFT exhibited a typical TFT transfer characteristic (semiconducting behavior). X-ray photoelectron spectroscopy revealed that, in contrast to what is commonly true in many oxides, oxygen vacancies (V(O)) in VZTO did not provide a dominant contribution to the total carrier concentration, because the V(O) peak area in the single VZTO film was 5.4% and reduced to 4.5% in VZTO/ZTO bilayer. Instead, Sn 3d5/2 and V 2p3/2 spectra suggest that the significant reduction in Sn and V ions is strongly related to the insulator-like behavior of the VZTO film. In negative-bias illumination tests and illumination tests with various photon energies, the VZTO/ZTO bilayer TFT had much better stability than the ZTO TFT. This result is attributed to the reduction of donor-like states ([Formula: see text]O) that can be positively ionized by blue and green illumination.
Collapse
Affiliation(s)
- Myeong Gu Yun
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea
| | - Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea
| | - Sung Woon Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea
| | - So Hee Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea
| | - Ye Kyun Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea
| | - Hyung Koun Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea
| |
Collapse
|
18
|
Ahn CH, Lee JH, Lee JY, Cho HK. Correlation between nano-scale microstructural behavior and the performance of ZnO thin-film transistors. J Nanosci Nanotechnol 2014; 14:8969-8973. [PMID: 25970992 DOI: 10.1166/jnn.2014.10056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Binary ZnO active layers possessing a polycrystalline structure were deposited with various argon/oxygen flow ratios at 250 degrees C via sputtering. Then ZnO thin-film-transistors (TFTs) were fabricated without additional thermal treatments. As the oxygen content increased during the deposition, the preferred orientation along the (0002) was weakened and the rotation of the grains increased, and furthermore, less conducting films were observed. On the other hand, the reduced oxygen flow rate induced the formation of amorphous-like transition layers during the initial growth due to a high growth rate and high energetic bombardment of the adatoms. As a result, the amorphous phases at the gate dielectric/channel interface were responsible for the formation of a hump shape in the subthreshold region of the TFT transfer curve. In addition, the relationship between the crystal properties and the shift in the threshold voltage was experimentally confirmed by a hysteresis test.
Collapse
|
19
|
Ahn CH, Senthil K, Cho HK, Lee SY. Artificial semiconductor/insulator superlattice channel structure for high-performance oxide thin-film transistors. Sci Rep 2014; 3:2737. [PMID: 24061388 PMCID: PMC3781393 DOI: 10.1038/srep02737] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 09/04/2013] [Indexed: 11/09/2022] Open
Abstract
High-performance thin-film transistors (TFTs) are the fundamental building blocks in realizing the potential applications of the next-generation displays. Atomically controlled superlattice structures are expected to induce advanced electric and optical performance due to two-dimensional electron gas system, resulting in high-electron mobility transistors. Here, we have utilized a semiconductor/insulator superlattice channel structure comprising of ZnO/Al2O3 layers to realize high-performance TFTs. The TFT with ZnO (5 nm)/Al2O3 (3.6 nm) superlattice channel structure exhibited high field effect mobility of 27.8 cm(2)/Vs, and threshold voltage shift of only < 0.5 V under positive/negative gate bias stress test during 2 hours. These properties showed extremely improved TFT performance, compared to ZnO TFTs. The enhanced field effect mobility and stability obtained for the superlattice TFT devices were explained on the basis of layer-by-layer growth mode, improved crystalline nature of the channel layers, and passivation effect of Al2O3 layers.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 440-746, Republic of Korea
| | | | | | | |
Collapse
|
20
|
Abstract
We examine a prototype graphene field effect sensor for the study of the dielectric constant, pyroelectric coefficient, and ferroelectric polarization of 100-300 nm epitaxial (Ba,Sr)TiO3 thin films. Ferroelectric switching induces hysteresis in the resistivity and carrier density of n-layer graphene (n = 1-5) below 100 K, which competes with an antihysteresis behavior activated by the combined effects of electric field and temperature. We also discuss how the polarization asymmetry and interface charge dynamics affect the electronic properties of graphene.
Collapse
Affiliation(s)
- A Rajapitamahuni
- Department of Physics and Astronomy and ‡Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln , Nebraska 68588-0299, United States
| | | | | | | |
Collapse
|
21
|
Kim SY, Ahn CH, Lee JH, Kwon YH, Hwang S, Lee JY, Cho HK. p-Channel oxide thin film transistors using solution-processed copper oxide. ACS Appl Mater Interfaces 2013; 5:2417-2421. [PMID: 23461753 DOI: 10.1021/am302251s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Cu2O thin films were synthesized on Si (100) substrate with thermally grown 200-nm SiO2 by sol-gel spin coating method and postannealing under different oxygen partial pressure (0.04, 0.2, and 0.9 Torr). The morphology of Cu2O thin films was improved through N2 postannealing before O2 annealing. Under relatively high oxygen partial pressure of 0.9 Torr, the roughness of synthesized films was increased with the formation of CuO phase. Bottom-gated copper oxide (CuxO) thin film transistors (TFTs) were fabricated via conventional photolithography, and the electrical properties of the fabricated TFTs were measured. The resulting Cu2O TFTs exhibited p-channel operation, and field effect mobility of 0.16 cm2/(V s) and on-to-off drain current ratio of ∼1×10(2) were observed in the TFT device annealed at PO2 of 0.04 Torr. This study presented the potential of the solution-based process of the Cu2O TFT with p-channel characteristics for the first time.
Collapse
Affiliation(s)
- Sang Yun Kim
- Department of Materials Science and Engineering, KAIST, 291, 6 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
22
|
Ahn CH, Mohanta SK, Cho HK. Donor and acceptor dynamics of phosphorous doped ZnO nanorods with stable p-type conduction: photoluminescence and junction characteristics. J Nanosci Nanotechnol 2012; 12:5571-5576. [PMID: 22966612 DOI: 10.1166/jnn.2012.6224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We employed temperature-dependent photoluminescence (PL) to explain the donor and acceptor dynamics in phosphorus doped stable p-type P:ZnO nanorods. The room temperature PL revealed good crystalline and optical quality of P:ZnO nanorods. The 10 K PL spectrum exhibited a dominant acceptor bound exciton (A0X) or donor bound exciton (D0X) emission corresponding to p- and n-type P:ZnO nanorods, respectively. The donor-acceptor-pair (DAP) transitions exhibited different thermal dissociation energies for the p- and n-type P:ZnO nanorods, suggesting their different quenching channels. The quenching of the DAP transitions of the p-type ZnO:P nanorods was associated with the thermal dissociation of the DAP into free excitons, while the DAP transition of the n-type ZnO:P nanorods was quenched through the thermal dissociation of the shallow donor into free electrons. The rectifying behavior of a p-n homojunction diode formed by the p-type P:ZnO nanorods on n-type ZnO film confirmed the p-type conduction of the P:ZnO nanorods.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do, 440-746, Republic of Korea
| | | | | |
Collapse
|
23
|
Kim HS, Ahn CH, Park TS, Park HD, Koh KS, Ryoo ZY, Park SC, Lee S. Gene expression profiling of a cold-shocked earthworm Eisenia andrei. Cryo Letters 2012; 33:1-11. [PMID: 22434117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
To identify genes that are modulated under cold-stress conditions in the earthworm Eisenia andrei, we performed a genome-wide analysis of gene expression in cold-shocked earthworms by using Serial Analysis of Gene Expression (SAGE). We identified 5,977 and 5,407 unique SAGE tags under normal and cold-stressed conditions, respectively. The majority of the SAGE tags did not match to any known expressed sequences, due to a paucity of expression data in earthworms. We converted the statistically significant SAGE tags for the cold-stressed condition into expressed sequence tags (ESTs), and the results showed that particular genes associated with energy homeostasis, cellular defense mechanisms, and ion balance were up-regulated or down-regulated. We constructed a regulatory network of some of these genes and identified rps-6 as a core gene in the cold-response regulatory-gene network. Our data provide a baseline for gene expression studies of cold shock in the Lumbricidae.
Collapse
Affiliation(s)
- H S Kim
- School of Life Science and Biotechnology, Kyungpook National University, Seoul, Republic of Korea
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Segal Y, Garrity KF, Vaz CAF, Hoffman JD, Walker FJ, Ismail-Beigi S, Ahn CH. Dynamic evanescent phonon coupling across the La(1-x)Sr(x)MnO3/SrTiO3 interface. Phys Rev Lett 2011; 107:105501. [PMID: 21981508 DOI: 10.1103/physrevlett.107.105501] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Indexed: 05/31/2023]
Abstract
The transport and magnetic properties of correlated La0.53Sr0.47MnO3 ultrathin films, grown epitaxially on SrTiO3, show a sharp cusp at the structural transition temperature of the substrate. Using a combination of experiment and first principles theory we show that the cusp is a result of evanescent cross-interface coupling between the charge carriers in the film and a soft phonon mode in the SrTiO3, mediated through linked oxygen octahedral motions. The amplitude of the mode diverges at the transition temperature, and phonons are launched into the first few atomic layers of the film, affecting its electronic state.
Collapse
Affiliation(s)
- Y Segal
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520-8284, USA
| | | | | | | | | | | | | |
Collapse
|
25
|
Hoffman J, Hong X, Ahn CH. Device performance of ferroelectric/correlated oxide heterostructures for non-volatile memory applications. Nanotechnology 2011; 22:254014. [PMID: 21572192 DOI: 10.1088/0957-4484/22/25/254014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Ferroelectric field effect devices offer the possibility of non-volatile data storage. Attempts to integrate perovskite ferroelectric materials with silicon semiconductors, however, have been largely unsuccessful in creating non-volatile, nondestructive read memory elements because of difficulties in controlling the ferroelectric/semiconductor interface. Correlated oxide systems have been explored as alternative channel materials to form all-perovskite field effect devices. We examine a non-volatile memory using an electric-field-induced metal-insulator transition in PbZr(0.2)Ti(0.8)O(3)/La(1 - x)Sr(x)MnO(3) (PZT/LSMO), PZT/La(1 - x)Ca(x)MnO(3) (PZT/LCMO) and PZT/La(1 - x)Sr(x)CoO(3) (PZT/LSCO) devices. The performance of these devices in the areas of switching time and retention are discussed.
Collapse
Affiliation(s)
- J Hoffman
- Department of Applied Physics and CRISP, Yale University, New Haven, CT 06511, USA.
| | | | | |
Collapse
|
26
|
Jang A, Lee KK, Bishop PL, Kim IS, Ahn CH. Development of polymer lab-on-a-chip (LOC) for oxidation-reduction potential (ORP) measurement. Water Sci Technol 2011; 63:2309-2315. [PMID: 21977654 DOI: 10.2166/wst.2011.645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Reverse osmosis (RO) desalination has been recognized as a promising method to solve the water shortage problem. Nevertheless, since it is energy intensive and has many problems associated with biofouling/fouling of RO membranes in RO plants, its commercial acceptance is still slow. Especially, as high levels of oxidizing agents negatively affect RO membrane efficiency and life span. So, there is a need to develop sensitive, selective, portable and rapid methods to determine oxidation-reduction potential (ORP) in feed solution. For developing a polymer ORP lab-on-a-chip (LOC), a microchannel patterned on a polymer substrate was successfully filled with 800 nm diameter silica beads using self-assembly bead packing technology. The measured ORPs using the three kinds of redox potential solutions were typically slightly lower than those of the nominal redox potential. But, all of the measurements should be deemed acceptable. The ORP LOC has also a much shorter response time than the conventional potentiometric sensor.
Collapse
Affiliation(s)
- A Jang
- Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, South Korea.
| | | | | | | | | |
Collapse
|
27
|
Ahn CH, Kim YY, Cho HK. Influence of synthesis temperature on the properties of Ga-doped ZnO nanorods grown by thermal evaporation. J Nanosci Nanotechnol 2011; 11:458-462. [PMID: 21446476 DOI: 10.1166/jnn.2011.3196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This study examined the effect of the synthesis temperatures on the characteristics of vertically aligned Ga-doped ZnO (GZO) nanorods grown on a ZnO template by thermal evaporation using Zn and Ga sources. The increase in synthesis temperature at less than 700 degrees C induced stress relaxation relative to the ZnO template due to the suppression of defect generation by the formation of nanorods, while a further increase resulted in an increase in compressive strain due to dominant Ga doping. The increase in Ga concentration in the GZO nanorods with increasing synthesis temperature was also confirmed by X-ray photoelectron spectroscopy and photoluminescence. The best conductivity was observed in the GZO nanorods grown at 800 degrees C. On the other hand, the GZO nanorods synthesized at 900 degrees C showed less conductivity and weak near-band-edge emission properties due to the generation of defects from the excess Ga.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746, Korea
| | | | | |
Collapse
|
28
|
Kolpak AM, Walker FJ, Reiner JW, Segal Y, Su D, Sawicki MS, Broadbridge CC, Zhang Z, Zhu Y, Ahn CH, Ismail-Beigi S. Interface-induced polarization and inhibition of ferroelectricity in epitaxial SrTiO₃/Si. Phys Rev Lett 2010; 105:217601. [PMID: 21231354 DOI: 10.1103/physrevlett.105.217601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2010] [Indexed: 05/30/2023]
Abstract
We use SrTiO₃/Si as a model system to elucidate the effect of the interface on ferroelectric behavior in epitaxial oxide films on silicon. Using both first-principles computations and synchrotron x-ray diffraction measurements, we show that structurally imposed boundary conditions at the interface stabilize a fixed (pinned) polarization in the film but inhibit ferroelectric switching. We demonstrate that the interface chemistry responsible for these phenomena is general to epitaxial silicon-oxide interfaces, impacting on the design of silicon-based functional oxide devices.
Collapse
Affiliation(s)
- A M Kolpak
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520-8284, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Ahn CH, Woo CH, Hwang S, Lee JY, Cho HK, Cho HJ, Yeom GY. Influence of active layer thickness and annealing in zinc oxide TFT grown by atomic layer deposition. SURF INTERFACE ANAL 2010. [DOI: 10.1002/sia.3357] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
30
|
Bae YS, Kim DC, Ahn CH, Kim JH, Cho HK. Growth of ZnO nanorod arrays by hydrothermal method using homo-seed layers annealed at various temperatures. SURF INTERFACE ANAL 2010. [DOI: 10.1002/sia.3262] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
31
|
Vaz CAF, Hoffman J, Segal Y, Reiner JW, Grober RD, Zhang Z, Ahn CH, Walker FJ. Origin of the magnetoelectric coupling effect in Pb(Zr0.2Ti0.8)O{3}/La{0.8}Sr{0.2}MnO{3} Multiferroic heterostructures. Phys Rev Lett 2010; 104:127202. [PMID: 20366560 DOI: 10.1103/physrevlett.104.127202] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Indexed: 05/29/2023]
Abstract
The electronic valence state of Mn in Pb(Zr0.2Ti0.8)O{3}/La{0.8}Sr{0.2}MnO{3} multiferroic heterostructures is probed by near edge x-ray absorption spectroscopy as a function of the ferroelectric polarization. We observe a temperature independent shift in the absorption edge of Mn associated with a change in valency induced by charge carrier modulation in the La0.8Sr0.2MnO3, demonstrating the electronic origin of the magnetoelectric effect. Spectroscopic, magnetic, and electric characterization shows that the large magnetoelectric response originates from a modified interfacial spin configuration, opening a new pathway to the electronic control of spin in complex oxide materials.
Collapse
Affiliation(s)
- C A F Vaz
- Department of Applied Physics and CRISP, Yale University, New Haven, Connecticut 06520, USA.
| | | | | | | | | | | | | | | |
Collapse
|
32
|
Hong X, Posadas A, Zou K, Ahn CH, Zhu J. High-mobility few-layer graphene field effect transistors fabricated on epitaxial ferroelectric gate oxides. Phys Rev Lett 2009; 102:136808. [PMID: 19392391 DOI: 10.1103/physrevlett.102.136808] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Indexed: 05/27/2023]
Abstract
The carrier mobility mu of few-layer graphene (FLG) field-effect transistors increases tenfold when the SiO2 substrate is replaced by single-crystal epitaxial Pb(Zr0.2Ti0.8)O3 (PZT). In the electron-only regime of the FLG, mu reaches 7x10(4) cm(2)/V s at 300 K for n=2.4x10(12)/cm(2), 70% of the intrinsic limit set by longitudinal acoustic (LA) phonons; it increases to 1.4x10(5) cm(2)/V s at low temperature. The temperature-dependent resistivity rho(T) reveals a clear signature of LA phonon scattering, yielding a deformation potential D=7.8+/-0.5 eV.
Collapse
Affiliation(s)
- X Hong
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | | | | | | | | |
Collapse
|
33
|
Segal Y, Reiner JW, Kolpak AM, Zhang Z, Ismail-Beigi S, Ahn CH, Walker FJ. Atomic structure of the epitaxial BaO/Si(001) interface. Phys Rev Lett 2009; 102:116101. [PMID: 19392218 DOI: 10.1103/physrevlett.102.116101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Indexed: 05/27/2023]
Abstract
We present the structure of the interface responsible for epitaxy of crystalline oxides on silicon. Using synchrotron x-ray diffraction, we observe a 2 x 1 unit cell reconstruction at the interface of BaO grown on Si(001) terminated with 1/2 ML of Sr. Since this symmetry is not present in bulk BaO or Si, only the interface contributes to diffracted intensity. First principles calculations accurately predict the observed diffraction and identify the structure of the BaO/Si interface, including the elemental composition and a sub-A rumpling due to epitaxial strain of the 7 adjacent BaO and Si layers.
Collapse
Affiliation(s)
- Y Segal
- Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520-8284, USA
| | | | | | | | | | | | | |
Collapse
|
34
|
Abstract
Vertically well-aligned Ga-doped ZnO nanorods with different Ga content were grown by thermal evaporation on a ZnO template. The Ga-doped ZnO nanorods synthesized with 50 wt% Ga with respect to the Zn content showed minimum compressive stress relative to the ZnO template, which led to a rapid growth rate along the c-axis due to the rapid release of stored strain energy. A further increase in the Ga content improved the conductivity of the nanorods due to the substitutional incorporation of Ga atoms in the Zn sites based on a decrease in lattice spacing. A p-n diode structure with Ga-doped ZnO nanorods as an n-type layer displayed a distinct white light luminescence from the side view of the device, showing weak ultraviolet and various deep-level emissions.
Collapse
Affiliation(s)
- Cheol Hyoun Ahn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do, 440-746, Korea
| | | | | | | |
Collapse
|
35
|
Jang A, Zou Z, MacKnight E, Wu PM, Kim IS, Ahn CH, Bishop PL. Development of a portable analyzer with polymer lab-on-a-chip (LOC) for continuous sampling and monitoring of Pb(II). Water Sci Technol 2009; 60:2889-2896. [PMID: 19934510 DOI: 10.2166/wst.2009.727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A new portable analyzer with polymer lab-on-a-chip (LOC) has been designed, fabricated and fully characterized for continuous sampling and monitoring of lead (Pb(II)) in this work. As the working electrodes of the sensor, bismuth (Bi (III)) which allowed the advantage of being more environmentally friendly than traditional mercury drop electrodes was used, while maintaining similar sensitivity and other desirable characteristics. The size of a portable analyzer was 30 cmx23 cmx7 cm, and the weight was around 3 kg. The small size gives the advantage of being portable for field use while not sacrificing portability for accuracy of measurement. Furthermore, the autonomous system developed in coordination with the development of new polymer LOC integrated with electrochemical sensors can provide an innovative way to monitor surface waters in an efficient, cost-effective and sustainable manner.
Collapse
Affiliation(s)
- A Jang
- Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, OH, USA.
| | | | | | | | | | | | | |
Collapse
|
36
|
Reiner JW, Garrity KF, Walker FJ, Ismail-Beigi S, Ahn CH. Role of strontium in oxide epitaxy on silicon (001). Phys Rev Lett 2008; 101:105503. [PMID: 18851225 DOI: 10.1103/physrevlett.101.105503] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Indexed: 05/26/2023]
Abstract
Epitaxial oxide-Si heterostructures, which integrate the functionality of crystalline oxides with Si technology, are made possible by a submonolayer of Sr deposited on Si (001). We find by electron diffraction studies using single termination Si wafers that this Sr submonolayer replaces the top layer of Si when deposited at 650 degrees C. Supported by first-principles calculations, we propose a model for the reaction dynamics of Sr on the Si surface and its effect on oxide epitaxy. This model predicts, and we experimentally confirm, an unexplored 25 degrees C pathway to crystalline oxide epitaxy on Si.
Collapse
Affiliation(s)
- J W Reiner
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520-8284, USA.
| | | | | | | | | |
Collapse
|
37
|
Ahn CH, Park HD, Lee YO, Park JK. Appearance of novel G-bacteria belonging to acidobacteria in a dairy wastewater treatment plant. Environ Technol 2008; 29:497-504. [PMID: 18661733 DOI: 10.1080/09593330801984530] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A dairy wastewater treatment plant operates a sequencing batch reactor (SBR) and stimulates enhanced biological phosphorus removal (EBPR) process with alternating anaerobic and aerobic cycles. Occasionally, the plant suffers from a high suspended solids problem in the supernatant. Interestingly, the occurrence of high suspended solids coincided with times when the EBPR process failed to remove phosphorus. To find out if there was a relationship between the EBPR failure and the high suspended solids problem, effluent samples were collected from the site during the period of poor phosphorus removal and examined microscopically. It was found that cocci-shaped bacteria (3-4 microm in diameter) were abundant in the effluent samples and they were clustered in tetrads. These were believed to be G-bacteria and results of both Gram and Neisser staining tests were negative, suggesting that they had few intracellular polyphosphate granules. Using polymerase chain reaction (PCR), cloning and deoxyribonucleic acid (DNA) sequence analysis, the phylogenetic information of in situ G-bacteria was obtained. It was found that all of the recovered clones were clustered in the phylum of Acidobacteria.
Collapse
MESH Headings
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- Dairying
- Microscopy, Electron, Scanning
- Microscopy, Phase-Contrast
- Phosphorus/metabolism
- Phylogeny
- Polymerase Chain Reaction
- Proteobacteria/genetics
- Proteobacteria/growth & development
- Proteobacteria/isolation & purification
- Proteobacteria/metabolism
- RNA, Ribosomal, 16S/chemistry
- RNA, Ribosomal, 16S/genetics
- Waste Disposal, Fluid/methods
- Water Pollutants, Chemical/metabolism
Collapse
Affiliation(s)
- C H Ahn
- Department of Civil and Environmental Engineering, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | | | | | | |
Collapse
|
38
|
Park GY, Im YH, Ahn CH, Park JW, Jeong SW, Ahn JY, Hwang YJ. Functional and genetic assessment of IFN-gamma receptor in patients with clinical tuberculosis. Int J Tuberc Lung Dis 2004; 8:1221-7. [PMID: 15527154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023] Open
Abstract
OBJECTIVE The molecular basis of the genetic vulnerability underlying the most common form of clinical tuberculosis (TB) remains largely unknown. We speculated that mild genetic defects in the interferon-gamma (IFN-gamma) signalling pathway caused a subtle functional impairment of IFN-gamma which would explain susceptibility to Mycobacterium tuberculosis in clinical TB. DESIGN A case-control study. RESULTS We evaluated functional responsiveness to IFN-gamma in monocytes from patients with clinical TB (n = 10), and analysed the genetic sequences of the IFN-gamma receptor 1 (IFN-gammaR1) and STAT1 genes in patients with disseminated TB (n = 18). IFN-gamma stimulated an increase in the expression of HLA-DR and CD64 on monocytes of both controls and patients; the rate of increase in expression was the same in both groups. Treatment with IFN-gamma before lipopolysaccharide (LPS) stimulation further increased tumour necrosis factor-alpha (TNF-alpha) production as compared to TNF-alpha production with LPS stimulation alone; the rate of increase in TNF-alpha production was the same in both groups. The known mutations in the coding sequences of the IFN-gammaR1 and STAT1 genes were not found in the patients with disseminated tuberculosis. CONCLUSION These results suggest that impairment of the IFN-gamma signalling pathway did not account for cases of clinical TB in this study.
Collapse
Affiliation(s)
- G Y Park
- Department of Internal Medicine, Gachon Medical School, Gil Medical Centre, Incheon, South Korea.
| | | | | | | | | | | | | |
Collapse
|
39
|
Abstract
Ferroelectric oxide materials have offered a tantalizing potential for applications since the discovery of ferroelectric perovskites more than 50 years ago. Their switchable electric polarization is ideal for use in devices for memory storage and integrated microelectronics, but progress has long been hampered by difficulties in materials processing. Recent breakthroughs in the synthesis of complex oxides have brought the field to an entirely new level, in which complex artificial oxide structures can be realized with an atomic-level precision comparable to that well known for semiconductor heterostructures. Not only can the necessary high-quality ferroelectric films now be grown for new device capabilities, but ferroelectrics can be combined with other functional oxides, such as high-temperature superconductors and magnetic oxides, to create multifunctional materials and devices. Moreover, the shrinking of the relevant lengths to the nanoscale produces new physical phenomena. Real-space characterization and manipulation of the structure and properties at atomic scales involves new kinds of local probes and a key role for first-principles theory.
Collapse
Affiliation(s)
- C H Ahn
- Departments of Applied Physics and Physics, Yale University, Post Office Box 208284, New Haven, CT 06520-8284, USA.
| | | | | |
Collapse
|
40
|
Abstract
Semiconducting field-effect transistors are the workhorses of the modern electronics era. Recently, application of the field-effect approach to compounds other than semiconductors has created opportunities to electrostatically modulate types of correlated electron behaviour--including high-temperature superconductivity and colossal magnetoresistance--and potentially tune the phase transitions in such systems. Here we provide an overview of the achievements in this field and discuss the opportunities brought by the field-effect approach.
Collapse
Affiliation(s)
- C H Ahn
- Department of Applied Physics, Yale University, PO Box 208284, New Haven, Connecticut 06520-8284, USA.
| | | | | |
Collapse
|
41
|
Gariglio S, Ahn CH, Matthey D, Triscone JM. Electrostatic tuning of the hole density in NdBa2Cu3O(7-delta) films and its effect on the Hall response. Phys Rev Lett 2002; 88:067002. [PMID: 11863843 DOI: 10.1103/physrevlett.88.067002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2001] [Indexed: 05/23/2023]
Abstract
We have used the ferroelectric field effect in heterostructures based on superconducting NdBa2-Cu(3)O(7-delta) and ferroelectric Pb(Zr0.2Ti0.8)O3 to electrostatically modulate in a reversible and nonvolatile fashion the hole carrier density of the superconducting layer. Reversing the ferroelectric polarization induces a constant relative change in the resistivity and Hall constant of 9% and 6%, respectively, at all temperatures above the superconducting transition. The cotangent of the Hall angle displays a T2 dependence with a slope that increases as the carrier density is reduced.
Collapse
Affiliation(s)
- S Gariglio
- DPMC, University of Geneva, 24 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland
| | | | | | | |
Collapse
|
42
|
Starkey DE, Han A, Bao JJ, Ahn CH, Wehmeyer KR, Prenger MC, Halsall HB, Heineman WR. Fluorogenic assay for beta-glucuronidase using microchip-based capillary electrophoresis. J Chromatogr B Biomed Sci Appl 2001; 762:33-41. [PMID: 11589456 DOI: 10.1016/s0378-4347(01)00313-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Microchip capillary electrophoresis (CE) was used with a model enzyme assay to demonstrate its potential application to combinatorial drug screening. Hydrolysis with beta-glucuronidase of the conjugated glucuronide, fluorescein mono-beta-D-glucuronide (FMG), liberated the fluorescent product, fluorescein. FMG and fluorescein were detected by fluorescence, with excitation and emission at 480 and 520 nm, respectively. Microchip CE was used to separate FMG and fluorescein. Fluorescein production was monitored to assess beta-glucuronidase activity. Michaelis-Menten enzyme kinetics analysis yielded the Km value. The results were compared with those from experiments done by conventional CE. The Km value for beta-glucuronidase with FMG is being reported for the first time as 18 microM. The inhibition of beta-glucuronidase by the competitive inhibitor D-saccharic acid-1,4-lactone (SL) was also determined using microchip CE. Reactions were done with various concentrations of inhibitor and constant beta-glucuronidase and FMG concentrations. A dose-response plot was acquired and the IC50 value for SL was determined to be 3 microM.
Collapse
Affiliation(s)
- D E Starkey
- Department of Chemistry, University of Cincinnati, OH 45221-0172, USA
| | | | | | | | | | | | | | | |
Collapse
|
43
|
Kim JS, Bae JS, Kim KH, Ahn CH, Oh SJ, Jeon HM, Lim KW, Chun CS. Clinical Analysis of PTEN, p53 and Her-2/neu Expressions in Thyroid Cancers. Cancer Res Treat 2001; 33:433-7. [PMID: 26680819 DOI: 10.4143/crt.2001.33.5.433] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
PURPOSE The dual-specificity phosphatase PTEN/ MMAC1/TEP1 has recently been identified as the tumor suppressor gene most frequently mutated and/or deleted in human tumors. However, PTEN mutations have rarely been detected in sporadic thyroid cancers. Therefore, this study investigated the PTEN expression of thyroid cancer and the relationship between PTEN, clinical status and other biologic factors such as HER-2/neu and p53. MATERIALS AND METHODS The study samples consisted of 62 thyroid cancer specimens and 24 benign thyroid tumor specimens from patients who were operated on the Department of Surgery, Uijongbu St. Mary's hospital during the 5 years from January 1995 until January 2000. All tumors were studied by immunohistochemical staining using monoclonal antibodies against PTEN, HER-2/neu and p53. The results were analyzed statistically. RESULTS PTEN protein was found to be under-expressed more frequently in thyroid cancers (29%) than in benign thyroid tumors (4.2%). The reduction in PTEN expression in thyroid cancers was not significantly related with the recorded clinical factors such as size, age, lymph node metastasis and p53, except for HER-2 which was found to be significantly related (p=0.001). HER-2 over- expression was noted in thyroid cancer (83.8%) more frequently than in benign tumors (16.7%). CONCLUSION This study has demonstrated that the under-expression of PTEN protein and the over-expression of HER-2 protein may play a role in the carcinogenesis and development of thyroid cancer.
Collapse
|
44
|
Abstract
Neurons may be particularly susceptible to oxidative damage, which has been proposed to induce somatic mutations, particularly in mitochondrial DNA (mtDNA). Therefore, acquired mtDNA mutations might preferentially accumulate in the brain and could play a role in aging and neurodegenerative disorders. Recently, a somatic T to G mtDNA mutation at noncoding nucleotide position 414 was reported in fibroblasts specifically from elderly subjects, with mutational burdens of up to 50%. We screened for this mutation in brain-derived mtDNA from 8 Alzheimer's disease patients, 27 Parkinson's disease patients, 4 multiple system atrophy patients, and 44 controls using up to three RFLP analyses. A total of 73 of these subjects were over the age of 65. The 414 mutation was absent in all cases. Next, individual mtDNA fragments from 6 elderly subjects were cloned, and a total of 70 clones were sequenced. The 414 mutation was absent in all clones, though occasional sequence variations were identified at other sites in single clones. The 414 mutation also was absent in blood (n = 6) and fibroblasts (n = 11) from elderly subjects. Our data suggest that it is rare for any one particular acquired mtDNA mutation to reach levels in the brain that are functionally significant. This does not exclude the possibility that the cumulative burden of multiple, individually rare, acquired mutations impairs mitochondrial function.
Collapse
Affiliation(s)
- D K Simon
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02115, USA.
| | | | | | | | | | | | | |
Collapse
|
45
|
Abstract
A new planar bio-magnetic bead separator on a glass chip has been designed, fabricated and tested. The separator is composed of micromachined semi-encapsulated spiral electromagnets and fluid channels, which have been separately fabricated and then bonded. The device was tested with super-paramagnetic beads of mean diameter 1 microm which were suspended in a buffered solution. When a DC current of 300 mA was applied to the inductor, the bio-magnetic beads were successfully separated on the electromagnets, showing a functional capability as a magnetic bead separator. To evaluate separation rate and capability, the inductance measurement method has been introduced and the inductance variation according to the separation rate has been characterized. Using this separator, cells or cell fragments and magnetic beads bonded with protein or enzyme suspended in bio-buffer solutions can be successfully separated from their suspensions, envisaging a filterless bio-separator.
Collapse
Affiliation(s)
- J W Choi
- Center for Microelectronic Sensors and MEMS, Department of Electrical and Computer Engineering and Computer Science, University of Cincinnati, PO Box 210030, Cincinnati, OH 45221-0030, USA.
| | | | | |
Collapse
|
46
|
Abstract
Gasless endoscopic surgery was applied to a thyroidectomy. Compared with the previous method of endoscopic thyroidectomy, this method is superior in obtaining hemostasis and minimizing the possible complications of gas-insufflating surgery, such as a hypercapnia or massive subcutaneous emphysema. We successfully removed 37 thyroid tumors in 35 patients by gasless endoscopic surgery without any significant complications. No scars remained in the neck, and all patients were satisfied with the cosmetic results. Gasless endoscopic thyroidectomy is a safe and technically feasible alternative to conventional thyroidectomy for cases of benign thyroid tumors and has good cosmetic results.
Collapse
Affiliation(s)
- J S Kim
- Department of General Surgery, Uijongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Kyunggi-do, South Korea.
| | | | | | | | | | | |
Collapse
|
47
|
Yan J, Kowel ST, Cho HJ, Ahn CH. Real-time full-color three-dimensional display with a micromirror array. Opt Lett 2001; 26:1075-1077. [PMID: 18049524 DOI: 10.1364/ol.26.001075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We designed, realized, and tested what is believed to be the first real-time, full-color, autostereoscopic three-dimensional (3-D) display with a micromirror array. Compared with the diffractive partial pixel architecture [Opt. Lett. 20, 1418 (1995)], this approach has certain advantages:(1) Micromirrors are reflective and thus achromatic (panchromatic) and (2) a variety of displays can be used as the image source. We used backlit transparencies to test the system and then used an ordinary color CRT to show several computer-generated full-color 3-D animations.
Collapse
|
48
|
Affiliation(s)
- J H Lee
- Department of Diagnostic Radiology, Our Lady of Mercy Hospital, College of Medicine, The Catholic University of Korea, 665 Pupyungdong, Pupyonggu, Incheon, 403-016 Korea
| | | | | | | | | | | | | |
Collapse
|
49
|
Abstract
The polarization field of the ferroelectric oxide lead zirconate titanate [Pb(ZrxTi1-x)O3] was used to tune the critical temperature of the hightemperature superconducting cuprate gadolinium barium copper oxide (GdBa2Cu3O7-x) in a reversible, nonvolatile fashion. For slightly underdoped samples, a uniform shift of several Kelvin in the critical temperature was observed, whereas for more underdoped samples, an insulating state was induced. This transition from superconducting to insulating behavior does not involve chemical or crystalline modification of the material.
Collapse
Affiliation(s)
- CH Ahn
- Departement de Physique de la Matiere Condensee, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | | | | | | | | | | |
Collapse
|
50
|
DeGeorge JJ, Ahn CH, Andrews PA, Brower ME, Giorgio DW, Goheer MA, Lee-Ham DY, McGuinn WD, Schmidt W, Sun CJ, Tripathi SC. Regulatory considerations for preclinical development of anticancer drugs. Cancer Chemother Pharmacol 1998; 41:173-85. [PMID: 9443633 DOI: 10.1007/s002800050726] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The entry of new anticancer treatments into phase I clinical trials is ordinarily based on relatively modest preclinical data. This report defines the battery of preclinical tests important for assessing safety under an Investigational New Drug application (IND) and outlines a basis for extrapolating starting doses of investigational anticancer drugs in phase I clinical trials from animal toxicity studies. Types of preclinical studies for the support of marketing of a new anticancer drug are also discussed. This report addresses differences and similarities in the preclinical development of cytotoxic drugs (including photosensitizers and targeted delivery products), drugs used chronically (chemopreventive drugs, hormonal drugs, immunomodulators), and drugs intended to enhance the efficacy (MDR-reversing agents and radiation/chemotherapy sensitizers) or diminish the toxicity of currently used anticancer therapies. Factors to consider in the design of preclinical studies of combination therapies, alternative therapies, and adjuvant therapies in the treatment of cancer, and to support changes in clinical formulations or route of administration, are also discussed.
Collapse
Affiliation(s)
- J J DeGeorge
- Division of Oncology Drug Products, Center for Drug Evaluation and Research, Food and Drug Administration, Rockville, Maryland 20857, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|