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Yusa H, Fujihisa H. Dense Structure of Yttrium Nitride as a Post-Rock-Salt Phase: High-Pressure Experiments and Computations. Inorg Chem 2022; 61:20906-20912. [PMID: 36503234 DOI: 10.1021/acs.inorgchem.2c03317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The post-rock-salt (B1) phase in yttrium nitride was investigated under pressures above 100 GPa. The starting B1 phase was prepared by a direct elemental reaction between yttrium metal and supercritical nitrogen in a laser-heated diamond anvil cell. Compression of the resulting compound under nitrogen pressure revealed that the experimental bulk modulus was significantly lower than that reported for previous compression experiments but consistent with values predicted by theoretical calculations. The post-B1 phase transition started at 116 GPa and was almost completed at 170 GPa, with slow kinetics of conversion. In contrast to the likely transformation to B2 from B1, the phase was determined to be B10, which is identical to a high-pressure BaO structure. Theoretical enthalpy calculation demonstrated that a transition from B1 to B10 takes place at 108 GPa prior to the B2 transition. The present YN is the first non-4f-nitride compound reported to crystallize with a B10 structure.
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Affiliation(s)
- Hitoshi Yusa
- National Institute for Materials Science, 1-1 Namiki (NIMS), Tsukuba, Ibaraki 305-0044, Japan
| | - Hiroshi Fujihisa
- National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
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2
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Affiliation(s)
- Jijun Zhao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Qiuying Du
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Si Zhou
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Vijay Kumar
- Center for Informatics, School of Natural Sciences, Shiv Nadar University, NH-91, Tehsil Dadri, Gautam Buddha Nagar 201314, U. P., India
- Dr. Vijay Kumar Foundation, 1969 Sector 4, Gurgaon 122001, Haryana, India
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Zhang Z, Chai C, Zhang W, Song Y, Kong L, Yang Y. First-Principles Study on III-Nitride Polymorphs: AlN/GaN/InN in the Pmn2 1 Phase. MATERIALS 2020; 13:ma13143212. [PMID: 32707645 PMCID: PMC7412507 DOI: 10.3390/ma13143212] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/12/2020] [Accepted: 07/14/2020] [Indexed: 01/06/2023]
Abstract
The structural, mechanical, and electronic properties, as well as stability, elastic anisotropy and effective mass of AlN/GaN/InN in the Pmn21 phase were determined using density functional theory (DFT). The phonon dispersion spectra and elastic constants certify the dynamic and mechanical stability at ambient pressure, and the relative enthalpies were lower than those of most proposed III-nitride polymorphs. The mechanical properties reveal that Pmn21-AlN and Pmn21-GaN possess a high Vickers hardness of 16.3 GPa and 12.8 GPa. Pmn21-AlN, Pmn21-GaN and Pmn21-InN are all direct semiconductor materials within the HSE06 hybrid functional, and their calculated energy band gaps are 5.17 eV, 2.77 eV and 0.47 eV, respectively. The calculated direct energy band gaps and mechanical properties of AlN/GaN/InN in the Pmn21 phase reveal that these three polymorphs may possess great potential for industrial applications in the future.
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Wonglakhon T, Zahn D. Interaction potentials for modelling GaN precipitation and solid state polymorphism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:205401. [PMID: 31961336 DOI: 10.1088/1361-648x/ab6cbe] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We outline a molecular mechanics model for the interaction of gallium and nitride ions ranging from small complexes to nanoparticles and bulk crystals. While the current GaN force fields allow the modelling of either bulk crystals or single ions dispersed in solution, our model covers both and hence paves the way to describing aggregate formation and crystal growth processes from molecular simulations. The key to this is the use of formal +3 and -3 charges on the gallium and nitride ions, whilst accounting for the charge transfer in GaN crystals by means of additional potential energy terms. The latter are fitted against experimental data of GaN in the wurtzite structure and benchmarked for the zinc-blende and rock-salt polymorphs. Comparison to quantum chemical references and experiment shows reasonable agreement of structures and formation energy of [GaN] n aggregates, elastic properties of the bulk crystal, the transition pressure of the wurtzite to rock-salt transformation and intrinsic point defects. Furthermore, we demonstrate force field transferability towards the modelling of GaN nanoparticles from simulated annealing runs.
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Affiliation(s)
- Tanakorn Wonglakhon
- Lehrstuhl für Theoretische Chemie/Computer Chemie Centrum, Friedrich-Alexander Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany
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5
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Daoud S, Bouarissa N. Elastic, piezoelectric and thermal properties of zinc-blende AlN under pressure. Theor Chem Acc 2019. [DOI: 10.1007/s00214-019-2439-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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6
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Ghafoor N, Petrov I, Holec D, Greczynski G, Palisaitis J, Persson POA, Hultman L, Birch J. Self-structuring in Zr 1-xAl xN films as a function of composition and growth temperature. Sci Rep 2018; 8:16327. [PMID: 30397271 PMCID: PMC6218527 DOI: 10.1038/s41598-018-34279-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 10/03/2018] [Indexed: 11/19/2022] Open
Abstract
Nanostructure formation via surface-diffusion-mediated segregation of ZrN and AlN in Zr1−xAlxN films during high mobility growth conditions is investigated for 0 ≤ × ≤ 1. The large immiscibility combined with interfacial surface and strain energy balance resulted in a hard nanolabyrinthine lamellar structure with well-defined (semi) coherent c-ZrN and w-AlN domains of sub-nm to ~4 nm in 0.2 ≤ × ≤ 0.4 films, as controlled by atom mobility. For high AlN contents (x > 0.49) Al-rich ZrN domains attain wurtzite structure within fine equiaxed nanocomposite wurtzite lattice. Slow diffusion in wurtzite films points towards crystal structure dependent driving force for decomposition. The findings of unlikelihood of iso-structural decomposition in c-Zr1−xAlxN, and stability of w-Zr1−xAlxN (in large × films) is complemented with first principles calculations.
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Affiliation(s)
- N Ghafoor
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden.
| | - I Petrov
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden.,Materials Science Department, and Frederick Seitz Materials Research Laboratory, University of Illinois, 104 S. Goodwin Avenue, Urbana, Illinois, 61801, USA
| | - D Holec
- Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Strasse 18, A-8700, Leoben, Austria
| | - G Greczynski
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden
| | - J Palisaitis
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden
| | - P O A Persson
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden
| | - L Hultman
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden
| | - J Birch
- Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden
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Fan Q, Zhang W, Yun S, Xu J, Song Y. III-Nitride Polymorphs: XN (X=Al, Ga, In) in the Pnma
Phase. Chemistry 2018; 24:17280-17287. [PMID: 30117614 DOI: 10.1002/chem.201803202] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Qingyang Fan
- School of Information and Control Engineering; Xi'an University of Architecture and Technology; Xi'an 710055 P. R. China
| | - Wenzhu Zhang
- School of Information and Control Engineering; Xi'an University of Architecture and Technology; Xi'an 710055 P. R. China
| | - Sining Yun
- Functional Materials Laboratory (FML); School of Materials & Mineral Resources; Xi'an University of Architecture and Technology; Xi'an 710055 P. R. China
| | - Jie Xu
- School of Information and Control Engineering; Xi'an University of Architecture and Technology; Xi'an 710055 P. R. China
| | - Yanxing Song
- School of Microelectronics; Xidian University; Xi'an 710071 P. R. China
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You D, Xu C, Qin F, Zhu Z, Manohari AG, Xu W, Zhao J, Liu W. Interface control for pure ultraviolet electroluminescence from nano-ZnO-based heterojunction devices. Sci Bull (Beijing) 2018; 63:38-45. [PMID: 36658916 DOI: 10.1016/j.scib.2017.12.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Revised: 11/14/2017] [Accepted: 11/28/2017] [Indexed: 01/21/2023]
Abstract
Realization of pure and stable ultraviolet electroluminescence (UV EL) of ZnO light-emitting diode (LED) is still a challenging issue, due to complicated defects of intrinsic ZnO and the corresponding device interfaces. In this paper, we demonstrated a simple & feasible method to fabricate n-ZnO/AlN/p-GaN heterojunctions light-emitting devices. First, the vertically aligned ZnO nanorods (NRs) have been prepared as high quality active layer, and the nanostructured heterojunction LED arrays were constructed by directly bonding ZnO NRs onto AlN-coated p-GaN wafer. By optimizing the AlN layer thickness to be 20 nm, a strong and pure ultraviolet emission located at 387 nm can be observed. The energy band alignment of n-ZnO/AlN (20 nm)/p-GaN heterojunction LED has been studied by using X-ray photoelectron spectroscopy (XPS), the valence band offset between AlN and GaN was calculated to be 0.34 eV. On the other side, the conduction band offset (as large as 3.28 eV) between AlN and ZnO can block the flow of electrons from ZnO to p-GaN. Thus, electron-hole recombination takes place in the ZnO layer, and a pure UV EL could be observed. Our results provide a significant approach toward future of pure ultraviolet optoelectronic LEDs.
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Affiliation(s)
- Daotong You
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - Chunxiang Xu
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China.
| | - Feifei Qin
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - Zhu Zhu
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - A Gowri Manohari
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - Wei Xu
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - Jie Zhao
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - Wei Liu
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
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9
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Zhang J, Qi J, Ma Y, Hu T, Yan J, Ke F, Cui X, Gao Y, Sun M, Gao C. Correlation between the structural change and the electrical transport properties of indium nitride under high pressure. Phys Chem Chem Phys 2017; 19:26758-26764. [PMID: 28948241 DOI: 10.1039/c7cp05105k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report on the intriguing structural and electrical transport properties of compressed InN. Pronounced anomalies of the resistivity, Hall coefficient, electron concentration, and mobility are observed at ∼11.5 GPa, accompanied by a wurtzite-rocksalt structural transition confirmed using high-pressure XRD measurements and first-principles calculations. The pressure-tuned electrical properties of wurtzite and rocksalt InN are also studied, respectively. Particularly, compression pressure significantly decreases the electron concentration of rocksalt InN by two orders of magnitude and increases the mobility by ten fold. The obvious variations in electrical parameters can be rationalized by our band structure simulations, which reveal a direct-indirect energy crossover at 10 GPa, followed by the rapidly increasing patterns of the energy gap with a pressure coefficient of 33 meV GPa-1. Moreover the electron effective mass and energy gap are found to well satisfy with the k·p model. Definite correlation between the structural change and the electrical transport properties should shed a new light on building InN-based applications in the future.
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Affiliation(s)
- Junkai Zhang
- Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping, 136000, China
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10
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Łepkowski SP, Bardyszewski W. Topological phase transition and evolution of edge states in In-rich InGaN/GaN quantum wells under hydrostatic pressure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:055702. [PMID: 27941228 DOI: 10.1088/1361-648x/29/5/055702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Combining the k · p method with the third-order elasticity theory, we perform a theoretical study of the pressure-induced topological phase transition and the pressure evolution of topologically protected edge states in InN/GaN and In-rich InGaN/GaN quantum wells. We show that for a certain range of the quantum well parameters, thanks to a negative band gap pressure coefficient, it is possible to continuously drive the system from the normal insulator state through the topological insulator into the semimetal phase. The critical pressure for the topological phase transition depends not only on the quantum well thickness but also on the width of the Hall bar, which determines the coupling between the edge states localized at the opposite edges. We also find that in narrow Hall bar structures, near the topological phase transition, a significant Rashba-type spin splitting of the lower and upper branches of the edge state dispersion curve appears. This effect originates from the lack of the mirror symmetry of the quantum well potential caused by the built-in electric field, and can be suppressed by increasing the Hall bar width. When the pressure increases, the energy dispersion of the edge states becomes more parabolic-like and the spin splitting decreases. A further increase of pressure leads to the transition to a semimetal phase, which occurs due to the closure of the indirect 2D bulk band gap. The difference between the critical pressure at which the system becomes semimetallic, and the pressure for the topological phase transition, correlates with the variation of the pressure coefficient of the band gap in the normal insulator state.
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Affiliation(s)
- S P Łepkowski
- Institute of High Pressure Physics 'Unipress', Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warszawa, Poland
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11
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Liu S, Li C, Figiel JJ, Brueck SRJ, Brener I, Wang GT. Continuous and dynamic spectral tuning of single nanowire lasers with subnanometer resolution using hydrostatic pressure. NANOSCALE 2015; 7:9581-9588. [PMID: 25952721 DOI: 10.1039/c5nr01855b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report continuous, dynamic, reversible, and widely tunable lasing from 367 to 337 nm from single GaN nanowires (NWs) by applying hydrostatic pressure up to ∼7 GPa. The GaN NW lasers, with heights of 4-5 μm and diameters ∼140 nm, are fabricated using a lithographically defined two-step top-down technique. The wavelength tuning is caused by an increasing Γ direct bandgap of GaN with increasing pressure and is precisely controllable to subnanometer resolution. The observed pressure coefficients of the NWs are ∼40% larger compared with GaN microstructures fabricated from the same material or from reported bulk GaN values, revealing a nanoscale-related effect that significantly enhances the tuning range using this approach. This approach can be generally applied to other semiconductor NW lasers to potentially achieve full spectral coverage from the UV to IR.
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Affiliation(s)
- Sheng Liu
- Sandia National Laboratories, Albuquerque, NM 87185, USA.
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12
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Majewski JA, Städele M, Vogl P. Electronic structure of biaxially strained wurtzite crystals GaN, AlN, and InN. ACTA ACUST UNITED AC 2014. [DOI: 10.1557/s1092578300002027] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We present first-principles studies of the effect of biaxial (0001)-strain on the electronic structure of wurtzite GaN, AlN, and InN. We provide accurate predictions for the valence band splittings as a function of strain which greatly facilitates the interpretation of data from samples with unintentional growth-induced strain. The present calculations are based on the total-energy pseudopotential method within the local-density formalism and include the spin-orbit interaction nonperturbatively. For a given biaxial strain, all structural parameters are determined by minimization of the total energy with respect to the electronic and ionic degrees of freedom. Our calculations predict that the valence band state Γ9(Γ6) lies energetically above the Γ7(Γ1) states in GaN and InN, in contrast to the situation in AlN. In all three nitrides, we find that the ordering of these two levels becomes reversed for some value of biaxial strain. In GaN, this crossing takes place already at 0.32% tensile strain. For larger tensile strains, the top of the valence band becomes well separated from the lower states. The computed crystal-field and spin-orbit splittings in unstrained materials as well as the computed deformation potentials agree well with the available experimental data.
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Bechstedt F, Belabbes A. Structure, energetics, and electronic states of III-V compound polytypes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:273201. [PMID: 23778868 DOI: 10.1088/0953-8984/25/27/273201] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Recently several hexagonal polytypes such as 2H, 4H, and 6H have been discovered for conventional III-V semiconductor compounds in addition to the cubic 3C zinc-blende polytype by investigating nanorods grown in the [111] direction in different temperature regimes. Also III-mononitrides crystallizing in the hexagonal 2H wurtzite structure under ambient conditions can be deposited in zinc-blende geometry using various growth techniques. The polytypic crystal structures influence the local electronic properties and the internal electric fields due to the spontaneous polarization in non-cubic crystals.In this paper we give a comprehensive review on the thermodynamic, structural, and electronic properties of twelve Al, Ga, and In antimonides, arsenides, phosphides, and nitrides as derived from ab initio calculations. Their lattice parameters, energetic stability, and characteristic band structure energies are carefully discussed and related to the atomic geometries of the polytypes. Chemical trends are investigated. Band offsets between polytypes and their consequences for heterocrystalline structures are derived. The described properties are discussed in the light of available experimental data and previous computations. Despite several contradictory results in the literature, a unified picture of the III-V polytypes and their heterocrystalline structures is developed.
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Affiliation(s)
- Friedhelm Bechstedt
- Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, D-07743 Jena, Germany.
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14
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Kaur P, Sekhon SS, Kumar V. Prediction of rock salt structure of (InN)32 nanoparticles from first principles calculations. J Chem Phys 2013; 138:114310. [DOI: 10.1063/1.4795580] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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15
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Saad Saoud F, Claude Plenet J, Henini M. [Not Available]. PHYSICA. B, CONDENSED MATTER 2012; 407:1008-1013. [PMID: 22485065 PMCID: PMC3299643 DOI: 10.1016/j.physb.2011.12.129] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 12/25/2011] [Accepted: 12/26/2011] [Indexed: 05/31/2023]
Abstract
The structural, electronic and vibrational properties of InN under pressures up to 20 GPa have been investigated using the pseudo-potential plane wave method (PP-PW). The generalized-gradient approximation (GGA) in the frame of density functional theory (DFT) approach has been adopted. It is found that the transition from wurtzite (B4) to rocksalt (B1) phase occurs at a pressure of approximately 12.7 GPa. In addition, a change from a direct to an indirect band gap is observed. The mechanism of these changes is discussed. The phonon frequencies and densities of states (DOS) are derived using the linear response approach and density functional perturbation theory (DFPT). The properties of phonons are described by the harmonic approximation method. Our results show that phonons play an important role in the mechanism of phase transition and in the instability of B4 (wurtzite) just before the pressure of transition. At zero pressure our data agree well with recently reported experimental results.
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Affiliation(s)
- Fatma Saad Saoud
- Department of Physics, Faculty of Sciences, C. University of Bordj Bou-Arreridj, (LMSE), Algeria
| | - Jean Claude Plenet
- University of Lyon, University of Lyon I, LPMCN, CNRS UMR 5586, 69622 Villeurbanne, France
| | - Mohamed Henini
- School of Physics & Astronomy and Nottingham Nanotechnology and Nanoscience Centre (NNNC) University of Nottingham, Nottingham NG7 2RD, UK
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16
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Usman Z, Cao C, Khan WS, Mahmood T, Hussain S, Nabi G. Structural, elastic constant, and vibrational properties of wurtzite gallium nitride: a first-principles approach. J Phys Chem A 2011; 115:14502-9. [PMID: 22044256 DOI: 10.1021/jp207141k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Perdew-Wang proposed generalized gradient approximation (GGA) is used in conjunction with ultrasoft pseudopotential to investigate the structural, elastic constant, and vibrational properties of wurtzite GaN. The equilibrium lattice parameters, axial ratio, internal parameter, bulk modulus, and its pressure derivative are calculated. The effect of pressure on equilibrium lattice parameters, axial ratio, internal parameter (u), relative volume, and bond lengths parallel and perpendicular to the c-axis are discussed. At 52 GPa, the relative volume change is observed to be 17.8%, with an abrupt change in bond length. The calculated elastic constants are used to calculate the shear wave speeds in the [100] and [001] planes. The finite displacement method is employed to calculate phonon frequencies and the phonon density of states. The first- and second-order pressure derivative and volume dependent Gruneisen parameter (γ(j)) of zone-center phonon frequencies are discussed. These phonon calculations calculated at theoretical lattice constants agree well with existing literature.
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Affiliation(s)
- Zahid Usman
- Research Centre of Materials Science, School of Material Science and Engineering, Beijing Institute of Technology, Beijing, People's Republic of China
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17
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Saoud FS, Plenet J, Louail L, Maouche D. Mechanism of the phase transition in GaN under pressure up to 100GPa. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2010.11.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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18
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Koleske DD, Wickenden AE, Freitas JA, Kaplan R, Prokes SM. Surface Energy Constraints for Heteroepitaxial Growth on Compliant Substrates: Morphology of GaN Grown on Sc Layers. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-449-347] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTAn empirical relationship linking surface energy to bulk modulus is presented which suggests that the thermodynamic growth mode for heteroepitaxy on compliant substrates should be 3-D. As an example of this behavior, GaN growth on Sc is shown for various growth conditions. 2-D growth is obtained when the GaN is grown on top of a low temperature GaN nucleation layer. Our results indicate that surface and interface energies, in addition to, lattice matching and thermal matching play an important role in determining the heteroexpitaxial growth morphology of GaN. There appears to be no net reduction in the dislocation density for GaN films grown on the Sc layers, because the GaN film has to be grown on a low temperature nucleation layer.
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Abstract
AbstractThe temperature dependence of the thermal expansion and the bulk modulus are critical for predicting the residual stress distribution in epitaxial films and provides information relevant for interatomic potentials and equations of state. The thermal expansions of aluminum nitride (AIN) and gallium nitride (GaN) are calculated with two models that employ the limited elastic and lattice parameter data. These semiempirical models allow prediction of the thermal expansions to higher temperatures. Calculated results are compared with experimental data.
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Xu MY, Xu M, Duan MY, Hu QP. Effect of Pressure on Electronic Structures and Optical Properties of Rocksalt InN. CHINESE J CHEM PHYS 2010. [DOI: 10.1088/1674-0068/23/03/293-296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Do EC, Shin YH, Lee BJ. Atomistic modeling of III-V nitrides: modified embedded-atom method interatomic potentials for GaN, InN and Ga(1-x)In(x)N. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:325801. [PMID: 21693973 DOI: 10.1088/0953-8984/21/32/325801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Modified embedded-atom method (MEAM) interatomic potentials for the Ga-N and In-N binary and Ga-In-N ternary systems have been developed based on the previously developed potentials for Ga, In and N. The potentials can describe various physical properties (structural, elastic and defect properties) of both zinc-blende and wurtzite-type GaN and InN as well as those of constituent elements, in good agreement with experimental data or high-level calculations. The potential can also describe the structural behavior of Ga(1-x)In(x)N ternary nitrides reasonably well. The applicability of the potentials to atomistic investigations of atomic/nanoscale structural evolution in Ga(1-x)In(x)N multi-component nitrides during the deposition of constituent element atoms is discussed.
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Affiliation(s)
- Eun Cheol Do
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
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Rebecca Römer S, Kroll P, Schnick W. A density functional study of the high-pressure chemistry of MSiN(2)(M = Be, Mg, Ca): prediction of high-pressure phases and examination of pressure-induced decomposition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:275407. [PMID: 21828491 DOI: 10.1088/0953-8984/21/27/275407] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Normal pressure modifications and tentative high-pressure phases of the nitridosilicates MSiN(2) with M = Be, Mg, or Ca have been thoroughly studied by density functional methods. At ambient pressure, BeSiN(2) and MgSiN(2) exhibit an ordered wurtzite variant derived from idealized filled β-cristobalite by a C1-type distortion. At ambient pressure, the structure of CaSiN(2) can also be derived from idealized filled β-cristobalite by a different type of distortion (D1-type). Energy-volume calculations for all three compounds reveal transition into an NaCl superstructure under pressure, affording sixfold coordination for Si. At 76 GPa BeSiN(2) forms an LiFeO(2)-type structure, corresponding to the stable ambient-pressure modification of LiFeO(2), while MgSiN(2) and CaSiN(2) adopt an LiFeO(2)-type structure, corresponding to a metastable modification (24 and 60 GPa, respectively). For both BeSiN(2) and CaSiN(2) intermediate phases appear (for BeSiN(2) a chalcopyrite-type structure and for CaSiN(2) a CaGeN(2)-type structure). These two tetragonal intermediate structures are closely related, differing mainly in their c/a ratio. As a consequence, chalcopyrite-type structures exhibit tetrahedral coordination for both cations (M and Si), whereas in CaGeN(2)-type structures one cation is tetrahedrally (Si) and one bisdisphenoidally (M) coordinated. Both structure types, chalcopyrite and CaGeN(2), can also be derived from idealized filled β-cristobalite through a B1-type distortion. The group-subgroup relation of the BeSiN(2)/MgSiN(2), the CaSiN(2), the chalcopyrite, the CaGeN(2) and the idealized filled β-cristobalite structure is discussed and the displacive phase transformation pathways are illustrated. The zero-pressure bulk moduli were calculated for all phases and have been found to be comparable to compounds such as α- Si(3)N(4), CaIrO(3) and Al(4)C(3). Furthermore, the thermodynamic stability of BeSiN(2), MgSiN(2) and CaSiN(2) against phase agglomerates of the binary nitrides M(3)N(2) and Si(3)N(4) under pressure are examined.
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Affiliation(s)
- S Rebecca Römer
- Department Chemie und Biochemie, Lehrstuhl für Anorganische Festkörperchemie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13 (D), D-81377 München, Germany
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23
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Grigoriev A, Sichel R, Lee HN, Landahl EC, Adams B, Dufresne EM, Evans PG. Nonlinear piezoelectricity in epitaxial ferroelectrics at high electric fields. PHYSICAL REVIEW LETTERS 2008; 100:027604. [PMID: 18232927 DOI: 10.1103/physrevlett.100.027604] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Indexed: 05/25/2023]
Abstract
Nonlinear effects in the coupling of polarization with elastic strain have been predicted to occur in ferroelectric materials subjected to high electric fields. Such predictions are tested here for a PbZr0.2Ti0.8O3 ferroelectric thin film at electric fields in the range of several hundred MV/m and strains reaching up to 2.7%. The piezoelectric strain exceeds predictions based on constant piezoelectric coefficients at electric fields from approximately 200 to 400 MV/m, which is consistent with a nonlinear effect predicted to occur at corresponding piezoelectric distortions.
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Affiliation(s)
- Alexei Grigoriev
- Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA
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24
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Jian SR. Mechanical Deformation Induced in Si and GaN Under Berkovich Nanoindentation. NANOSCALE RESEARCH LETTERS 2007; 3:6. [PMCID: PMC3244777 DOI: 10.1007/s11671-007-9106-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Accepted: 11/12/2007] [Indexed: 05/28/2023]
Abstract
Details of Berkovich nanoindentation-induced mechanical deformation mechanisms of single-crystal Si(100) and the metal-organic chemical-vapor deposition (MOCVD) derived GaN thin films have been systematic investigated by means of micro-Raman spectroscopy and cross-sectional transmission electron microscopy (XTEM) techniques. The XTEM samples were prepared by using focused ion beam (FIB) milling to accurately position the cross-section of the nanoindented area. The behaviors of the discontinuities displayed in the loading and unloading segments of the load-displacement curves of Si and GaN thin films performed with a Berkovich diamond indenter tip were explained by the observed microstructure features obtained from XTEM analyses. According to the observations of micro-Raman and XTEM, the nanoindentation-induced mechanical deformation is due primarily to the generation and propagation of dislocations gliding along the pyramidal and basal planes specific to the hexagonal structure of GaN thin films rather than by indentation-induced phase transformations displayed in Si.
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Affiliation(s)
- Sheng-Rui Jian
- Department of Materials Science and Engineering, I-Shou University, No.1, Sec.1, Syuecheng Rd., Dashu Township, Kaohsiung, 840, Taiwan
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25
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Warner JH, Hoshino A, Yamamoto K, Tilley RD. Water-soluble photoluminescent silicon quantum dots. Angew Chem Int Ed Engl 2006; 44:4550-4. [PMID: 15973756 DOI: 10.1002/anie.200501256] [Citation(s) in RCA: 284] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jamie H Warner
- School of Chemical and Physical Sciences, MacDiarmid Institute of Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand
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26
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27
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Uberuaga BP, Smith R, Cleave AR, Montalenti F, Henkelman G, Grimes RW, Voter AF, Sickafus KE. Structure and mobility of defects formed from collision cascades in MgO. PHYSICAL REVIEW LETTERS 2004; 92:115505. [PMID: 15089149 DOI: 10.1103/physrevlett.92.115505] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Indexed: 05/24/2023]
Abstract
We study radiation-damage events in MgO on experimental time scales by augmenting molecular dynamics cascade simulations with temperature accelerated dynamics, molecular statics, and density functional theory. At 400 eV, vacancies and mono- and di-interstitials form, but often annihilate within milliseconds. At 2 and 5 keV, larger clusters can form and persist. While vacancies are immobile, interstitials aggregate into clusters (In) with surprising properties; e.g., an I4 is immobile, but an impinging I2 can create a metastable I6 that diffuses on the nanosecond time scale but is stable for years.
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Affiliation(s)
- B P Uberuaga
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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28
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Hung A, Russo SP, McCulloch DG, Prawer S. An ab initio study of structural properties and single vacancy defects in Wurtzite AlN. J Chem Phys 2004; 120:4890-6. [PMID: 15267350 DOI: 10.1063/1.1645790] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The cell parameters, bulk moduli and electronic densities-of-states (DOS) of pure and vacancy defect AlN were computed using generalized-gradient approximation (GGA) and hybrid functional (B3LYP) computational methods within both plane wave-pseudopotential and localized Gaussian basis set approaches. All of the methods studied yielded cell parameters and bulk moduli in reasonable agreement with experiment. The B3LYP functional was also found to predict an optical band gap in excellent agreement with experiment. These methods were subsequently applied to the calculation of the geometry, defect state positions and formation energies of the cation (V(Al)) and anion (V(N)) single vacancy defects. For the V(Al) defect, the plane wave-pseudopotential predicted a significant retraction of the neighboring N away from the vacancy, while for the V(N) defect, only slight relaxations of the surrounding Al atoms towards the vacancy were predicted. For the computed DOS of both vacancy defects, the GGA methods yielded similar features and defect level positions relative to the valence band maximum, while the B3LYP method predicted higher separations between the defect levels and the valence and conduction bands, leading to higher energy occupied defect levels.
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Affiliation(s)
- Andrew Hung
- Department of Applied Physics, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001, Australia
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29
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Blumenau AT, Fall CJ, Elsner J, Jones R, Heggie MI, Frauenheim T. A theoretical investigation of dislocations in cubic and hexagonal gallium nitride. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pssc.200303126] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- A. T. Blumenau
- School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - C. J. Fall
- School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - J. Elsner
- Department of Physics, Faculty of Science, University of Paderborn, 33098 Paderborn, Germany
| | - R. Jones
- School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - M. I. Heggie
- CPES, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom
| | - T. Frauenheim
- Department of Physics, Faculty of Science, University of Paderborn, 33098 Paderborn, Germany
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30
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Dmitrienko VE, Ishida K. Comment on "Band structure approach to resonant X-ray scattering". PHYSICAL REVIEW LETTERS 2003; 90:129601-129602. [PMID: 12688913 DOI: 10.1103/physrevlett.90.129601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2002] [Indexed: 05/24/2023]
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31
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Lemoine D, Quattrucci JG, Jackson B. Efficient Eley-Rideal reactions of H atoms with single Cl adsorbates on Au(111). PHYSICAL REVIEW LETTERS 2002; 89:268302. [PMID: 12484860 DOI: 10.1103/physrevlett.89.268302] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2002] [Indexed: 05/24/2023]
Abstract
Density functional theory is used to construct an interaction model for H atoms with Cl over Au(111). Single-adsorbate Eley-Rideal reactions are investigated with quantum and quasiclassical methods. The reaction cross sections, amounting to 2-3 A(2), are much larger than for HD recombinations on metals. This can be traced to the adsorbed Cl being relatively far above the surface, the H-Cl interaction prevailing over the H-substrate attraction for a sizable range of impact parameters.
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Affiliation(s)
- Didier Lemoine
- Laboratoire de Physique des Lasers, Atomes et Molécules, UMR CNRS 8523, Centre d'Etudes et de Recherches Lasers et Applications, Université de Lille 1, Bâtiment P5, 59655 Villeneuve d'Ascq CEDEX, France
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32
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Meng S, Xu LF, Wang EG, Gao S. Vibrational recognition of hydrogen-bonded water networks on a metal surface. PHYSICAL REVIEW LETTERS 2002; 89:176104. [PMID: 12398690 DOI: 10.1103/physrevlett.89.176104] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2002] [Indexed: 05/24/2023]
Abstract
The adsorption of water on Pt(111) surface has been studied with ab initio molecular dynamics simulation. Both the energetics and vibrational dynamics indicate the existence of a well-ordered molecular bilayer on this surface. This conclusion is in contrast to the recent result of water on Ru(0001) surface, but agrees with available experiments. In addition, our calculation identifies two different hydrogen bonds in the bilayer. Both can be directly recognized from the vibrational spectra of the OH stretch modes.
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Affiliation(s)
- Sheng Meng
- Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing, 100080, China
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33
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Avishai Y, Meir Y. New spin-orbit-induced universality class in the integer quantum Hall regime. PHYSICAL REVIEW LETTERS 2002; 89:076602. [PMID: 12190544 DOI: 10.1103/physrevlett.89.076602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2001] [Indexed: 05/23/2023]
Abstract
Using heuristic arguments and numerical simulations it is argued that the critical exponent nu describing the localization length divergence at the integer quantum-Hall transition is modified in the presence of spin-orbit scattering with short-range correlations. The exponent is very close to nu=4/3, the percolation correlation length exponent, consistent with the prediction of a semiclassical argument. In addition, a band of weakly localized states is conjectured.
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Affiliation(s)
- Yshai Avishai
- Department of Physics and Ilse Katz Center for Meso- and Nanoscale Science and Technology, Ben Gurion University, Beer Sheva, Israel
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34
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Lee SS, Ahn JR, Kim ND, Min JH, Hwang CG, Chung JW, Yeom HW, Ryjkov SV, Hasegawa S. Adsorbate-induced pinning of a charge-density wave in a quasi-1D metallic chains: Na on the In/Si(111)-(4x1) surface. PHYSICAL REVIEW LETTERS 2002; 88:196401. [PMID: 12005651 DOI: 10.1103/physrevlett.88.196401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2001] [Indexed: 05/22/2023]
Abstract
We find that foreign adsorbates acting as local impurities can induce a metal-insulator transition by pinning a charge-density wave (CDW) on the quasi-1D metallic In/Si(111)-(4x1) chain system. Our scanning tunneling microscopy image clearly reveals the presence of a new local 4x2 structure nucleated by Na adatoms at room temperature, which turns out to be insulating with a doubled periodicity along the chains. We directly determine a CDW gap energy Delta = 105+/-8 meV by identifying a characteristic loss peak in our high-resolution electron-energy-loss spectra. We thus report the first observation of a local impurity-derived Peierls-like reconstruction of a quasi-1D system.
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Affiliation(s)
- S S Lee
- Physics Department and Basic Science Research Institute, Pohang University of Science and Technology, San 31 Hyoja Dong, Pohang 790-784, Korea
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35
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Shashkin AA, Kravchenko SV, Klapwijk TM. Metal-insulator transition in a 2D electron gas: equivalence of two approaches for determining the critical point. PHYSICAL REVIEW LETTERS 2001; 87:266402. [PMID: 11800848 DOI: 10.1103/physrevlett.87.266402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2001] [Indexed: 05/23/2023]
Abstract
The critical electron density for the metal-insulator transition in a two-dimensional electron gas can be determined by two distinct methods: (i) a sign change of the temperature derivative of the resistance, and (ii) vanishing activation energy and vanishing nonlinearity of current-voltage characteristics as extrapolated from the insulating side. We find that, in zero magnetic field (but not in the presence of a parallel magnetic field), both methods give equivalent results, adding support to the existence of a true zero-field metal-insulator transition.
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Affiliation(s)
- A A Shashkin
- Physics Department, Northeastern University, Boston, Massachusetts 02115, USA
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36
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Shashkin AA, Kravchenko SV, Dolgopolov VT, Klapwijk TM. Indication of the ferromagnetic instability in a dilute two-dimensional electron system. PHYSICAL REVIEW LETTERS 2001; 87:086801. [PMID: 11497969 DOI: 10.1103/physrevlett.87.086801] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2001] [Indexed: 05/23/2023]
Abstract
The magnetic field B(c), in which the electrons become fully spin polarized, is found to be proportional to the deviation of the electron density from the zero-field metal-insulator transition in a two-dimensional electron system in silicon. The tendency of B(c) to vanish at a finite electron density suggests a ferromagnetic instability in this strongly correlated electron system.
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Affiliation(s)
- A A Shashkin
- Physics Department, Northeastern University, Boston, Massachusetts 02115, USA
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37
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Healy SB, Filippi C, Kratzer P, Penev E, Scheffler M. Role of electronic correlation in the Si(100) reconstruction: a quantum Monte Carlo study. PHYSICAL REVIEW LETTERS 2001; 87:016105. [PMID: 11461481 DOI: 10.1103/physrevlett.87.016105] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2001] [Indexed: 05/23/2023]
Abstract
Recent low-temperature scanning tunneling experiments have questioned the generally accepted picture of buckled silicon dimers as the ground state reconstruction of the Si(100) surface, undermining the ability of density functional theory to accurately describe electronic correlations at surfaces. We present quantum Monte Carlo calculations on large cluster models of the surface, and conclude that buckling remains energetically favorable even when the present-day best treatment of electronic correlation is employed. The implications for experimental interpretation are discussed.
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Affiliation(s)
- S B Healy
- Physics Department, National University of Ireland, Cork, Ireland
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38
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Ahn H, Wu CL, Gwo S, Wei CM, Chou YC. Structure determination of the Si3N4/Si(111)- (8 x 8) surface: a combined study of Kikuchi electron holography, scanning tunneling microscopy, and ab initio calculations. PHYSICAL REVIEW LETTERS 2001; 86:2818-2821. [PMID: 11290047 DOI: 10.1103/physrevlett.86.2818] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2000] [Indexed: 05/23/2023]
Abstract
A comprehensive atomic model for the reconstructed surface of Si3N4 thin layer grown on Si(111) is presented. Kikuchi electron holography images clearly show the existence of adatoms on the Si3N4(0001)/Si(111)-(8x8) surface. Compared with the ab initio calculations, more than 30 symmetry-inequivalent atomic pairs in the outmost layers are successfully identified. Scanning tunneling microscopy (STM) images show diamond-shaped unit cells and nine adatoms in each cell. High-resolution STM images reveal extra features and are in good agreement with the partial charge density distribution obtained from total-energy calculations.
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Affiliation(s)
- H Ahn
- Department of Physics, National Tsing-Hua University, Hsinchu, Taiwan 300, Republic of China
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39
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Limpijumnong S, Lambrecht WR. Homogeneous Strain Deformation Path for the Wurtzite to Rocksalt High-Pressure Phase Transition in GaN. PHYSICAL REVIEW LETTERS 2001; 86:91-94. [PMID: 11136101 DOI: 10.1103/physrevlett.86.91] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2000] [Indexed: 05/23/2023]
Abstract
A homogeneous orthorhombic shear strain deformation path is proposed for the wurtzite to rocksalt high-pressure transformation. Its energetics are calculated from first-principles for GaN. Previous experimental and theoretical studies of the transition pressure are discussed.
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Affiliation(s)
- S Limpijumnong
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079
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40
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Chang CM, Wei CM, Chen SP. Self-diffusion of small clusters on fcc metal (111) surfaces. PHYSICAL REVIEW LETTERS 2000; 85:1044-1047. [PMID: 10991470 DOI: 10.1103/physrevlett.85.1044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/1999] [Indexed: 05/23/2023]
Abstract
We use ab initio density-functional theory supplemented with the embedded-atom method to study the self-diffusion of small clusters on the (111) surface of eight fcc metals. A zigzag motion is found to be important in the dimer and tetramer diffusions. The dimer diffuses by a zigzag and concerted motion. The trimer diffuses by a concerted three-atom motion. The tetramer diffuses through a zigzag motion where only two atoms move simultaneously in each step. Thus, instead of increasing, the migration energy is lowered (or stays constant) for the tetramer as compared to that for the trimer. This novel break of the upwards trend in migration energy is predicted to be a general phenomenon.
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Affiliation(s)
- CM Chang
- National Center for High-Performance Computing, Hsinchu, Taiwan 30043, Republic of China
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41
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Pertsev NA, Koukhar VG. Polarization instability in polydomain ferroelectric epitaxial thin films and the formation of heterophase structures. PHYSICAL REVIEW LETTERS 2000; 84:3722-3725. [PMID: 11019186 DOI: 10.1103/physrevlett.84.3722] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/1999] [Indexed: 05/23/2023]
Abstract
A thermodynamic theory is developed for dense laminar domain structures in epitaxial ferroelectric films. It is found that, at some critical misfit strain between the film and substrate, the 90 degrees c/a/c/a domain structure becomes unstable with respect to the appearance of the polarization component parallel to domain walls, which results in the formation of a heterophase structure. For PbTiO3 and BaTiO3 films, the stability ranges of polydomain and heterophase states are determined. Dielectric anomalies accompanying misfit-strain-driven structural transformations are described.
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Affiliation(s)
- NA Pertsev
- A. F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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42
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Hoppe H, Zulicke U, Schon G. Andreev reflection in strong magnetic fields. PHYSICAL REVIEW LETTERS 2000; 84:1804-1807. [PMID: 11017630 DOI: 10.1103/physrevlett.84.1804] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/1999] [Indexed: 05/23/2023]
Abstract
We have studied the interplay of Andreev reflection and cyclotron motion of quasiparticles at a superconductor-normal-metal interface with a strong magnetic field applied parallel to the interface. Bound states are formed due to the confinement introduced by both the external magnetic field and the superconducting gap. These bound states are a coherent superposition of electron and hole edge excitations similar to those realized in finite quantum-Hall samples. We find the energy spectrum for these Andreev edge states and calculate transport properties.
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Affiliation(s)
- H Hoppe
- Institut fur Theoretische Festkorperphysik, Universitat Karlsruhe, D-76128 Karlsruhe, Germany
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43
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Zhang SB, Branz HM. Nonradiative electron-hole recombination by a low-barrier pathway in hydrogenated silicon semiconductors. PHYSICAL REVIEW LETTERS 2000; 84:967-970. [PMID: 11017417 DOI: 10.1103/physrevlett.84.967] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/1999] [Indexed: 05/23/2023]
Abstract
A microscopic pathway for nonradiative electron-hole recombination by large structural reconfiguration in hydrogenated Si is found with first-principles calculations. Trapped-biexciton formation leads to a low-barrier reconfiguration of the H atom, accompanied by crossing of doubly occupied electron and hole levels in the band gap. This crossing represents the nonradiative recombination of the carriers, without multiphonon emission. The proposal provides a mechanism for carrier-induced H emission during metastable degradation of hydrogenated amorphous silicon.
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Affiliation(s)
- SB Zhang
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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44
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Robinson Brown A, Doren DJ. Energetics of silicon hydrides on the Si(100)-(2×1) surface. J Chem Phys 1998. [DOI: 10.1063/1.476814] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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45
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Cheng CL, Lin JC, Chang HC. The absolute absorption strength and vibrational coupling of CH stretching on diamond C(111). J Chem Phys 1997. [DOI: 10.1063/1.473701] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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46
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Schubert M, Rheinländer B, Franke E, Pietzonka I, Skriniarová J, Gottschalch V. Direct-gap reduction and valence-band splitting of ordered indirect-gap AlInP2 studied by dark-field spectroscopy. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:17616-17619. [PMID: 9985887 DOI: 10.1103/physrevb.54.17616] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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47
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Mestres N, Alsina F, Pascual J, Bluet JM, Camassel J, Geng C, Scholz F. Edge-on micro-Raman assessment of trigonal modes in partially ordered GaInP2. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:17754-17758. [PMID: 9985905 DOI: 10.1103/physrevb.54.17754] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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48
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Gavioli L, Betti MG, Mariani C. Dynamics-Induced Surface Metallization of Si(100). PHYSICAL REVIEW LETTERS 1996; 77:3869-3872. [PMID: 10062329 DOI: 10.1103/physrevlett.77.3869] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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49
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Bassi M, Camagni P, Rolli R, Samoggia G, Parmigiani F, Dhalenne G, Revcolevschi A. Optical absorption of CuGeO3. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:R11030-R11033. [PMID: 9984978 DOI: 10.1103/physrevb.54.r11030] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Winkelholz C, Fazio R, Hekking FW, Schön G. Anomalous Density of States of a Luttinger Liquid in Contact with a Superconductor. PHYSICAL REVIEW LETTERS 1996; 77:3200-3203. [PMID: 10062159 DOI: 10.1103/physrevlett.77.3200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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