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Xu M, Bian Z, Chen Q, Wang H, Chen C, Lu H. Polymeric microlens array formed on a discontinuous wetting surface using a self-assembly technique. APPLIED OPTICS 2024; 63:4380-4385. [PMID: 38856617 DOI: 10.1364/ao.518091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 05/08/2024] [Indexed: 06/11/2024]
Abstract
In this paper, we demonstrate a facile way to prepare polymeric microlens arrays (MLAs) based on a discontinuous wetting surface using a self-assembly technique. A patterned hydrophobic-octadecyltrichlorosilane (OTS) surface was prepared by U V/O 3 irradiation through a shadow mask. The area exposed to U V/O 3 irradiation turned highly hydrophilic, whereas the area protected by the mask remained highly hydrophobic, generating the patterned OTS surface. The surface energy of the OTS/glass surface changed from 23 to 72.8 mN/m after 17 min of U V/O 3 treatment. The scribing of the optical glue-NOA 81 onto the microhole array enabled one to obtain the MLAs due to the generation of the NOA 81 droplet array via the surface tension. After UV light curing, the cured NOA 81 droplet array with uniform dimensions within a large area exhibited excellent MLA characteristics. Moreover, the method developed in this study is simple in operation, low-cost, and requires neither a clean room nor expensive equipment.
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Yu Y, Joshi P, Bridges D, Fieser D, Hu A. Femtosecond Laser-Induced Nano-Joining of Volatile Tellurium Nanotube Memristor. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:789. [PMID: 36903667 PMCID: PMC10005240 DOI: 10.3390/nano13050789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 02/17/2023] [Accepted: 02/20/2023] [Indexed: 06/18/2023]
Abstract
Nanowire/nanotube memristor devices provide great potential for random-access high-density resistance storage. However, fabricating high-quality and stable memristors is still challenging. This paper reports multileveled resistance states of tellurium (Te) nanotube based on the clean-room free femtosecond laser nano-joining method. The temperature for the entire fabrication process was maintained below 190 °C. A femtosecond laser joining technique was used to form nanowire memristor units with enhanced properties. Femtosecond (fs) laser-irradiated silver-tellurium nanotube-silver structures resulted in plasmonic-enhanced optical joining with minimal local thermal effects. This produced a junction between the Te nanotube and the silver film substrate with enhanced electrical contacts. Noticeable changes in memristor behavior were observed after fs laser irradiation. Capacitor-coupled multilevel memristor behavior was observed. Compared to previous metal oxide nanowire-based memristors, the reported Te nanotube memristor system displayed a nearly two-order stronger current response. The research displays that the multileveled resistance state is rewritable with a negative bias.
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Affiliation(s)
- Yongchao Yu
- Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Knoxville, 1512 Middle Drive, Knoxville, TN 37996, USA
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| | - Pooran Joshi
- Oak Ridge National Lab, 1 Bethel Valley Rd., Oak Ridge, TN 37831, USA
| | - Denzel Bridges
- Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Knoxville, 1512 Middle Drive, Knoxville, TN 37996, USA
| | - David Fieser
- Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Knoxville, 1512 Middle Drive, Knoxville, TN 37996, USA
| | - Anming Hu
- Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Knoxville, 1512 Middle Drive, Knoxville, TN 37996, USA
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Zuo Y, Wang Z, Zhao H, Zhao L, Zhang L, Yi B, Bao W, Zhang Y, Su L, Yu Y, Xie J. Synthesis of a Spatially Confined, Highly Durable, and Fully Exposed Pd Cluster Catalyst via Sequential Site-Selective Atomic Layer Deposition. ACS APPLIED MATERIALS & INTERFACES 2022; 14:14466-14473. [PMID: 35312273 DOI: 10.1021/acsami.2c00009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Bottom-up synthesis based on site-selective atomic layer deposition is a powerful atomic-scale processing approach to fabricate materials with desired functionalities. Typical selective atomic layer deposition (ALD) can be achieved using selective activation of a growth area or selective deactivation of a protected area. In this work, we explored the site selectivity based on the difference of the inherent surface reactivity between different materials and within the same materials. By sequentially applying two site-selective atomic layer deposition, the ALD Pd catalyst is spatially confined on ALD SnO2 modified h-BN substrate Pd/SnO2/h-BN shows improved catalytic activity and stability due to strong metal-support interactions and spatial confinement. The results reveal that sequential site-selective ALD is a feasible and effective synthesis strategy that provides an attractive path toward designing and developing highly stable catalysts.
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Affiliation(s)
- Yuqing Zuo
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Zeyu Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Haojie Zhao
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Lianqi Zhao
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Lunjia Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Beili Yi
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Wenda Bao
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yue Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Longxing Su
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yi Yu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jin Xie
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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Senadheera DII, Kuruppu Arachchige NMK, Subasinghege Don V, Kumar R, Garno JC. Heterogeneous assembly of water from the vapor phase-Physical experiments and simulations with binding trifunctional organosilanes at the vapor/solid interface. J Chem Phys 2021; 154:214705. [PMID: 34240973 DOI: 10.1063/5.0046210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A trace amount of interfacial water is required to initiate hydrosilation reactions of trifunctional organosilanes to form surface assemblies. In recent studies, we have learned that water also has a critical role in directing molecular placement on surfaces because water can react with silicon to provide oxygenated sites for surface binding. Consequently, the wettability nature of substrates influences the placement and density of organosilane films formed by vapor-phase reactions. Nanopatterning protocols were designed using vapor-phase organosilanes and colloidal lithography to compare the wettability differences of hydrophilic mica(0001) compared to relatively hydrophobic Si(100) as a strategy for tracking the location of water on surfaces. The competition between hydrophobic and hydrophilic domains for the adsorption and coalescence of water condensed from vapor can be mapped indirectly by mapping the organosilanes, which bind to water at the solid interface, using atomic force microscopy. Trifunctional octadecyltrichlorosilane (OTS) was used as a marker molecule to map out the areas of the surface where water was deposited. The effect of systematic changes in film thickness and surface coverage of OTS was evaluated at the vapor/solid interface by adding an incremental amount of water to sealed reaction vessels to wet the surface and assessing the outcome after reaction with vapor-phase trichlorosilane. Reactive molecular dynamics simulations of the silicon-water vapor interface combined with electronic structure calculations of oxygenated silicon clusters with methyltrichlorosilane provided insight of the mechanism for surface binding, toward understanding the nature of the interface and wettability factors, which influence the association and placement of silane molecules on surfaces.
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Affiliation(s)
- D I I Senadheera
- Chemistry Department, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803, USA
| | | | - Visal Subasinghege Don
- Chemistry Department, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803, USA
| | - Revati Kumar
- Chemistry Department, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803, USA
| | - Jayne C Garno
- Chemistry Department, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803, USA
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Fetterly CR, Olsen BC, Luber EJ, Buriak JM. Vapor-Phase Nanopatterning of Aminosilanes with Electron Beam Lithography: Understanding and Minimizing Background Functionalization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:4780-4792. [PMID: 29614858 DOI: 10.1021/acs.langmuir.8b00679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Electron beam lithography (EBL) is a highly precise, serial method for patterning surfaces. Positive tone EBL resists enable patterned exposure of the underlying surface, which can be subsequently functionalized for the application of interest. In the case of widely used native oxide-capped silicon surfaces, coupling an activated silane with electron beam lithography would enable nanoscale chemical patterning of the exposed regions. Aminoalkoxysilanes are extremely useful due to their reactive amino functionality but have seen little attention for nanopatterning silicon surfaces with an EBL resist due to background contamination. In this work, we investigated three commercial positive tone EBL resists, PMMA (950k and 495k) and ZEP520A (57k), as templates for vapor-phase patterning of two commonly used aminoalkoxysilanes, 3-aminopropyltrimethoxysilane (APTMS) and 3-aminopropyldiisopropylethoxysilane (APDIPES). The PMMA resists were susceptible to significant background reaction within unpatterned areas, a problem that was particularly acute with APTMS. On the other hand, with both APTMS and APDIPES exposure, unpatterned regions of silicon covered by the ZEP520A resist emerged pristine, as shown both with SEM images of the surfaces of the underlying silicon and through the lack of electrostatically driven binding of negatively charged gold nanoparticles. The ZEP520A resist allowed for the highly selective deposition of these alkoxyaminosilanes in the exposed areas, leaving the unpatterned areas clean, a claim also supported by contact angle measurements with four probe liquids and X-ray photoelectron spectroscopy (XPS). We investigated the mechanistic reasons for the stark contrast between the PMMA resists and ZEP520A, and it was found that the efficacy of resist removal appeared to be the critical factor in reducing the background functionalization. Differences in the molecular weight of the PMMA resists and the resulting influence on APTMS diffusion through the resist films are unlikely to have a significant impact. Area-selective nanopatterning of 15 nm gold nanoparticles using the ZEP520A resist was demonstrated, with no observable background conjugation noted in the unexposed areas on the silicon surface by SEM.
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Affiliation(s)
- Christopher R Fetterly
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive , Edmonton , Alberta T6G 2M9 , Canada
| | - Brian C Olsen
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive , Edmonton , Alberta T6G 2M9 , Canada
| | - Erik J Luber
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive , Edmonton , Alberta T6G 2M9 , Canada
| | - Jillian M Buriak
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive , Edmonton , Alberta T6G 2M9 , Canada
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Xing S, Lin L, Zou G, Liu L, Peng P, Wu A, Duley WW, Zhou YN. Improving the electrical contact at a Pt/TiO 2 nanowire interface by selective application of focused femtosecond laser irradiation. NANOTECHNOLOGY 2017; 28:405302. [PMID: 28730997 DOI: 10.1088/1361-6528/aa8150] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this paper, we show that tightly focused femtosecond laser irradiation is effective in improving nanojoining of an oxide nanowire (NW) (TiO2) to a metal electrode (Pt), and how this process can be used to modify contact states. Enhanced chemical bondings are created due to localized plasmonically enhanced optical absorption at the Pt/TiO2 interface as confirmed by finite element simulations of the localized field distribution during irradiation. Nano Auger electron spectroscopy shows that the resulting heterojunction is depleted in oxygen, suggesting that a TiO2-x layer is formed between the Pt electrode and the TiO2 NW. The presence of this redox layer at the metal/oxide interface plays an important role in decreasing the Schottky barrier height and in facilitating chemical bonding. After laser irradiation at the cathode for 10 s at a fluence of 5.02 mJ cm-2, the Pt/TiO2 NW/Pt structure displays different electrical properties under forward and reverse bias voltage, respectively. The creation of this asymmetric electrical characteristic shows the way in which modification of the electronic interface by laser engineering can replace the electroforming process in resistive switching devices and how it can be used to control contact states in a metal/oxide interface.
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Affiliation(s)
- Songling Xing
- Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, People's Republic of China
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Sampson MD, Emery JD, Pellin MJ, Martinson ABF. Inhibiting Metal Oxide Atomic Layer Deposition: Beyond Zinc Oxide. ACS APPLIED MATERIALS & INTERFACES 2017; 9:33429-33436. [PMID: 28379011 DOI: 10.1021/acsami.7b01410] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au, and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H2-plasma pretreatment of the Au substrate prior to the gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles. We study the effect that the ALD precursor purge times, growth temperature, alkanethiol chain length, alkanethiol deposition time, and plasma treatment time have on Al2O3 ALD inhibition. This is the first example of Al2O3 ALD inhibition from a vapor-deposited SAM. The inhibitions of Al2O3, ZnO, and MnO ALD processes are compared, revealing the versatility of this selective surface treatment. Atomic force microscopy and grazing-incidence X-ray fluorescence further reveal insight into the mechanism by which the well-defined surface chemistry of ALD may eventually be circumvented to allow metal oxide nucleation and growth on SAM-modified surfaces.
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Affiliation(s)
- Matthew D Sampson
- Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Jonathan D Emery
- Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
- Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208, United States
| | - Michael J Pellin
- Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Alex B F Martinson
- Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
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Hlawacek G, Jankowski M, Wormeester H, van Gastel R, Zandvliet HJW, Poelsema B. Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision. Ultramicroscopy 2016; 162:17-24. [PMID: 26720438 DOI: 10.1016/j.ultramic.2015.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 11/13/2015] [Accepted: 11/17/2015] [Indexed: 11/17/2022]
Abstract
Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2-3 layers thick Ag/Pt alloy film. A periodicity of 6.65nm along the ⟨112⟩ surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by 1/√3 of a nearest neighbor spacing along ⟨112⟩. This periodicity is measured with atomic precision: coincidence between the Ag and the Pt lattices is observed for 23 Ag atoms on 24 Pt atoms. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy.
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Affiliation(s)
- Gregor Hlawacek
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Maciej Jankowski
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Herbert Wormeester
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Raoul van Gastel
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Harold J W Zandvliet
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Bene Poelsema
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
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Avila JR, DeMarco EJ, Emery JD, Farha OK, Pellin MJ, Hupp JT, Martinson ABF. Real-time observation of atomic layer deposition inhibition: metal oxide growth on self-assembled alkanethiols. ACS APPLIED MATERIALS & INTERFACES 2014; 6:11891-8. [PMID: 25046585 DOI: 10.1021/am503008j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Through in situ quartz crystal microbalance (QCM) monitoring, we resolve the growth of a self-assembled monolayer (SAM) and subsequent metal oxide deposition with high resolution. We introduce the fitting of mass deposited during each atomic layer deposition (ALD) cycle to an analytical island-growth model that enables quantification of growth inhibition, nucleation density, and the uninhibited ALD growth rate. A long-chain alkanethiol was self-assembled as a monolayer on gold-coated quartz crystals in order to investigate its effectiveness as a barrier to ALD. Compared to solution-loading, vapor-loading is observed to produce a SAM with equal or greater inhibition ability in minutes vs days. The metal oxide growth temperature and the choice of precursor also significantly affect the nucleation density, which ranges from 0.001 to 1 sites/nm(2). Finally, we observe a minimum 100 cycle inhibition of an oxide ALD process, ZnO, under moderately optimized conditions.
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Affiliation(s)
- Jason R Avila
- Department of Chemistry, Northwestern University , 2145 Sheridan Road Evanston, Illinois 60208, United States
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Liu H, Wu R, Du J, Nie X, Xu S, Wang J. Fabrication of polyelectrolyte/amine-modified silica composite thin film by coupling of layer-by-layer assembly and sol–gel techniques. JOURNAL OF POLYMER RESEARCH 2014. [DOI: 10.1007/s10965-013-0328-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Liu HH, Lin TH, Sheu JT. Self-assembled monolayer-based selective modification on polysilicon nanobelt devices. ACS APPLIED MATERIALS & INTERFACES 2013; 5:10048-10053. [PMID: 24025498 DOI: 10.1021/am402586q] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In this study, a self-assembled monolayer (SAM) of methoxy-poly (ethylene-glycol)-silane (mPEG-sil) was used to modify the silicon dioxide surface of polysilicon nanodevices (PNDs) to act as a passivation layer that inhibits nonspecific binding of proteins and reduces localized Joule heating power. Selective modifications of 3-aminopropyltrimethoxysilane (APTMS), NHS-biotin and dye-labeled Streptavidin on the removal regions were characterized. These PNDs, which consist of a two-level doping profile, were designed to confine heat in the low-level doping region during localized Joule heating. Localized Joule heating with pulse bias was examined in both vacuum and ambient, which indicated the removal region was longer in vacuum for the same pulse bias. Moreover, a comparison of selectively and nonselectively modified PNDs observed in time-lapsed fluorescence detection of dye-labeled Streptavidin showed a higher increasing rate in fluorescence intensity (∼2× enhancement) in the selectively modified PNDs. Finally, a COMSOL simulation was employed to evaluate the temperature distribution in the PNDs, with results showing that heat confinement was observed in the low-level doping region and a temperature very close to 673 K was achieved while applying a pulse voltage (40 V, 5 μs) to remove mPEG-sil.
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Affiliation(s)
- Hao Heng Liu
- Institute of Nanotechnology/Department of Materials Science and Engineering, National Chiao Tung University , 1001 Ta Hsueh Road, Hsinchu, Taiwan 30050
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Mussi V, Fanzio P, Firpo G, Repetto L, Valbusa U. Size and functional tuning of solid state nanopores by chemical functionalization. NANOTECHNOLOGY 2012; 23:435301. [PMID: 23060606 DOI: 10.1088/0957-4484/23/43/435301] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrate the possibility of using a simple functionalization procedure, based on an initial vapour-phase silanization, to control the size and functionality of solid state nanopores. The presented results show that, by varying the silanization time, it is possible to modify the efficiency of probe molecule attachment, thus shrinking the pore to the chosen size, while introducing a specific sensing selectivity. The proposed method allows us to tune the nanopore biosensor adapting it to the specific final application, and it can be efficiently applied when the pore initial diameter does not exceed a limit dimension related to the mean free path of the silane molecules at the working pressure.
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Affiliation(s)
- Valentina Mussi
- Nanomed Labs, Physics Department, University of Genova, Via Dodecaneso, 33 Genova, I-16146, Italy.
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Hlawacek G, Veligura V, Lorbek S, Mocking TF, George A, van Gastel R, Zandvliet HJW, Poelsema B. Imaging ultra thin layers with helium ion microscopy: Utilizing the channeling contrast mechanism. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2012; 3:507-12. [PMID: 23019545 PMCID: PMC3458595 DOI: 10.3762/bjnano.3.58] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/15/2012] [Indexed: 05/24/2023]
Abstract
BACKGROUND Helium ion microscopy is a new high-performance alternative to classical scanning electron microscopy. It provides superior resolution and high surface sensitivity by using secondary electrons. RESULTS We report on a new contrast mechanism that extends the high surface sensitivity that is usually achieved in secondary electron images, to backscattered helium images. We demonstrate how thin organic and inorganic layers as well as self-assembled monolayers can be visualized on heavier element substrates by changes in the backscatter yield. Thin layers of light elements on heavy substrates should have a negligible direct influence on backscatter yields. However, using simple geometric calculations of the opaque crystal fraction, the contrast that is observed in the images can be interpreted in terms of changes in the channeling probability. CONCLUSION The suppression of ion channeling into crystalline matter by adsorbed thin films provides a new contrast mechanism for HIM. This dechanneling contrast is particularly well suited for the visualization of ultrathin layers of light elements on heavier substrates. Our results also highlight the importance of proper vacuum conditions for channeling-based experimental methods.
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Affiliation(s)
- Gregor Hlawacek
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
| | - Vasilisa Veligura
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
| | - Stefan Lorbek
- Institute for Physics, Montanuniversitaet Leoben, Franz Josef Straße 18, 8700 Leoben, Austria
| | - Tijs F Mocking
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
| | - Antony George
- Inorganic Material Science, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
| | - Raoul van Gastel
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
| | - Harold J W Zandvliet
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
| | - Bene Poelsema
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands
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