The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
J. Furthmüller - One of the best experts on this subject based on the ideXlab platform.
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efficient iterative schemes for ab initio total energy calculations using a plane wave basis set
Physical Review B, 1996Co-Authors: Georg Kresse, J. FurthmüllerAbstract:We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and Amorphous Semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and Semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
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Efficiency of ab-initio total energy calculations for metals and Semiconductors using a plane-wave basis set
Computational Materials Science, 1996Co-Authors: Georg Kresse, J. FurthmüllerAbstract:We present a detailed description and comparison of algorithms for performing ab-initio quantum-mechanical calculations using pseudopotentials and a plane-wave basis set. We will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temperature density-functional theory, (b) iterative methods for the diagonalization of the Konn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atomsscaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge density including a new special 'preconditioning' optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. We have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio molecular-dynamics package). The program and the techniques have been used successfully for a large number of different systems (liquid and Amorphous Semiconductors, liquid simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and Semiconductors) and turned out to be very reliable.
Georg Kresse - One of the best experts on this subject based on the ideXlab platform.
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efficient iterative schemes for ab initio total energy calculations using a plane wave basis set
Physical Review B, 1996Co-Authors: Georg Kresse, J. FurthmüllerAbstract:We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and Amorphous Semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and Semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
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Efficiency of ab-initio total energy calculations for metals and Semiconductors using a plane-wave basis set
Computational Materials Science, 1996Co-Authors: Georg Kresse, J. FurthmüllerAbstract:We present a detailed description and comparison of algorithms for performing ab-initio quantum-mechanical calculations using pseudopotentials and a plane-wave basis set. We will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temperature density-functional theory, (b) iterative methods for the diagonalization of the Konn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atomsscaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge density including a new special 'preconditioning' optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. We have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio molecular-dynamics package). The program and the techniques have been used successfully for a large number of different systems (liquid and Amorphous Semiconductors, liquid simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and Semiconductors) and turned out to be very reliable.
Hideo Hosono - One of the best experts on this subject based on the ideXlab platform.
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material design of p type transparent Amorphous semiconductor cu sn i
Advanced Materials, 2018Co-Authors: Masato Sasase, Hideo HosonoAbstract:: Transparent Amorphous Semiconductors (TAS) that can be fabricated at low temperature are key materials in the practical application of transparent flexible electronics. Although various n-type TAS materials with excellent performance, such as Amorphous In-Ga-Zn-O (a-IGZO), are already known, no complementary p-type TAS has been realized to date. Here, a material design concept for p-type TAS materials is proposed utilizing the pseudo s-orbital nature of spatially spreading iodine 5p orbitals and Amorphous Sn-containing CuI (a-CuSnI) thin film is reported as an example. The resulting a-CuSnI thin films fabricated by spin coating at low temperature (140 °C) have a smooth surface. The Hall mobility increases with the hole concentration and the largest mobility of ≈9 cm2 V-1 s-1 is obtained, which is comparable with that of conventional n-type TAS.
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Transparent Amorphous oxide Semiconductors: Materials design, electronic structure, and device applications
2017 75th Annual Device Research Conference (DRC), 2017Co-Authors: Hideo HosonoAbstract:In 1995, I presented a materials design concept for transparent Amorphous oxide Semiconductors with a large electron mobility (TAOS) at the 16'h International conference on Amorphous Semiconductors along with concrete example materials of TAOS and the paper was published in 1996 [1[. The basic concept of TAOS is that large electron mobility should be retained even in Amorphous materials if the conduction band minimum is mainly composed of spatially large spread of metal ns-orbitals.1 The validity of this design concept was demonstrated by analysis of electronic structure using photoemission experiments combined with calculations based on X-ray structural analysis[2].
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material characteristics and applications of transparent Amorphous oxide Semiconductors
Npg Asia Materials, 2010Co-Authors: Toshio Kamiya, Hideo HosonoAbstract:Transparent Amorphous oxide Semiconductors have unique electron transport properties, such as large electron mobility (10–50 cm2/Vs) and the absence of a Hall voltage sign anomaly, that are not seen in conventional Amorphous Semiconductors. This class of materials has been attracting much attention as a channel layer in thin-film transistors (TFTs) utilizing the above features along with the processing advantage that thin films can be deposited at low temperatures by conventional sputtering methods. The primary driving force for this trend is a rapidly emerging demand for backplane TFTs that can drive the next generation of flat-panel displays. This article reviews the recent advances in fundamental science of these materials and their TFT applications. Emphasis is placed on the view that high ionicity in chemical bonding and large spherical spread of unoccupied metal s orbitals in p-block metal oxides lead to the realization of electronic structures that are advantageous for n-channel TFT applications. Amorphous oxide Semiconductors are compared with conventional hydrogenated Amorphous silicon, which is used widely as the channel material for backplane TFTs in current liquid-crystal displays.
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ionic Amorphous oxide Semiconductors material design carrier transport and device application
Journal of Non-crystalline Solids, 2006Co-Authors: Hideo HosonoAbstract:Abstract Recently we have reported the room temperature fabrication of transparent and flexible thin film transistors on a polyethylene terephthalate (PET) film substrate using an ionic Amorphous oxide semiconductor (IAOS) in an In2O3–ZnO–Ga2O3 system. These transistors exhibit a field effect mobility of ∼10 cm2 (V s)−1, which is higher by an order of magnitude than those of hydrogenated Amorphous Si and pentacene transistors. This article describes a chemical design concept of IAOS, and its unique electron transport properties, and electronic structure, by comparing them with those of conventional Amorphous Semiconductors. High potential of IAOS for flexible electronics is addressed.
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carrier transport and electronic structure in Amorphous oxide semiconductor a ingazno4
Thin Solid Films, 2005Co-Authors: Akihiro Takagi, Hiromichi Ohta, Kenji Nomura, Toshio Kamiya, Masahiro Hirano, Hiroshi Yanagi, Hideo HosonoAbstract:Abstract Carrier transport properties in Amorphous oxide semiconductor InGaZnO 4 (a-IGZO) thin films were investigated in detail using temperature dependence of Hall measurements. It was found that Hall mobility increased distinctly as carrier concentration increased. Unlikely conventional Amorphous Semiconductors such as a-Si/H, definite normal Hall voltage signals were observed on the films with carrier concentrations ( N e )>10 16 cm −3 , and Hall mobilities as large as 15 cm 2 (Vs) −1 were attained in the films with N e >10 20 cm −3 . When N e was less than 10 19 cm −3 , the temperature dependence of Hall mobility showed thermally-activated behavior in spite that carrier concentration was independent of temperature. While, it changed to almost degenerate conduction at N e >10 18 cm −3 . These behaviors are similar to those observed in single-crystalline IGZO, and are explained by percolation conduction through distributed potential barriers which are formed in the vicinity of the conduction band bottom due to the randomness of the Amorphous structure. The effective mass of a-IGZO was estimated to be ∼0.34 m e ( m e is the mass of free electron) from optical data, which is almost the same as that of crystalline IGZO (∼0.32 m e ).
F C Marques - One of the best experts on this subject based on the ideXlab platform.
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coefficient of thermal expansion and elastic modulus of thin films
Journal of Applied Physics, 1999Co-Authors: M M De Lima, R G Lacerda, J Vilcarromero, F C MarquesAbstract:The coefficient of thermal expansion (CTE), biaxial modulus, and stress of some Amorphous Semiconductors (a-Si:H, a-C:H, a-Ge:H, and a-GeCx:H) and metallic (Ag and Al) thin films were studied. The thermal expansion and the biaxial modulus were measured by the thermally induced bending technique. The stress of the metallic films, deposited by thermal evaporation (Ag and Al), is tensile, while that of the Amorphous films deposited by sputtering (a-Si:H, a-Ge:H, and a-GeCx:H) and by glow discharge (a-C:H) is compressive. We observed that the coefficient of thermal expansion of the tetrahedral Amorphous thin films prepared in this work, as well as that of the films reported in literature, depend on the network strain. The CTE of tensile films is smaller than that of their corresponding crystalline Semiconductors, but it is higher for compressive films. On the other hand, we found out that the elastic biaxial modulus of the Amorphous and metallic films is systematically smaller than that of their crystalline c...
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coefficient of thermal expansion and elastic modulus of thin films
Journal of Applied Physics, 1999Co-Authors: M M De Lima, R G Lacerda, J Vilcarromero, F C MarquesAbstract:The coefficient of thermal expansion (CTE), biaxial modulus, and stress of some Amorphous Semiconductors (a-Si:H, a-C:H, a-Ge:H, and a-GeCx:H) and metallic (Ag and Al) thin films were studied. The thermal expansion and the biaxial modulus were measured by the thermally induced bending technique. The stress of the metallic films, deposited by thermal evaporation (Ag and Al), is tensile, while that of the Amorphous films deposited by sputtering (a-Si:H, a-Ge:H, and a-GeCx:H) and by glow discharge (a-C:H) is compressive. We observed that the coefficient of thermal expansion of the tetrahedral Amorphous thin films prepared in this work, as well as that of the films reported in literature, depend on the network strain. The CTE of tensile films is smaller than that of their corresponding crystalline Semiconductors, but it is higher for compressive films. On the other hand, we found out that the elastic biaxial modulus of the Amorphous and metallic films is systematically smaller than that of their crystalline counterparts. This behavior stands for other films reported in the literature that were prepared by different techniques and deposition conditions. These differences were attributed to the reduction of the coordination number and to the presence of defects, such as voids and dangling bonds, in Amorphous films. On the other hand, columnar structure and microcrystallinity account for the reduced elasticity of the metallic films.
M M De Lima - One of the best experts on this subject based on the ideXlab platform.
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coefficient of thermal expansion and elastic modulus of thin films
Journal of Applied Physics, 1999Co-Authors: M M De Lima, R G Lacerda, J Vilcarromero, F C MarquesAbstract:The coefficient of thermal expansion (CTE), biaxial modulus, and stress of some Amorphous Semiconductors (a-Si:H, a-C:H, a-Ge:H, and a-GeCx:H) and metallic (Ag and Al) thin films were studied. The thermal expansion and the biaxial modulus were measured by the thermally induced bending technique. The stress of the metallic films, deposited by thermal evaporation (Ag and Al), is tensile, while that of the Amorphous films deposited by sputtering (a-Si:H, a-Ge:H, and a-GeCx:H) and by glow discharge (a-C:H) is compressive. We observed that the coefficient of thermal expansion of the tetrahedral Amorphous thin films prepared in this work, as well as that of the films reported in literature, depend on the network strain. The CTE of tensile films is smaller than that of their corresponding crystalline Semiconductors, but it is higher for compressive films. On the other hand, we found out that the elastic biaxial modulus of the Amorphous and metallic films is systematically smaller than that of their crystalline c...
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coefficient of thermal expansion and elastic modulus of thin films
Journal of Applied Physics, 1999Co-Authors: M M De Lima, R G Lacerda, J Vilcarromero, F C MarquesAbstract:The coefficient of thermal expansion (CTE), biaxial modulus, and stress of some Amorphous Semiconductors (a-Si:H, a-C:H, a-Ge:H, and a-GeCx:H) and metallic (Ag and Al) thin films were studied. The thermal expansion and the biaxial modulus were measured by the thermally induced bending technique. The stress of the metallic films, deposited by thermal evaporation (Ag and Al), is tensile, while that of the Amorphous films deposited by sputtering (a-Si:H, a-Ge:H, and a-GeCx:H) and by glow discharge (a-C:H) is compressive. We observed that the coefficient of thermal expansion of the tetrahedral Amorphous thin films prepared in this work, as well as that of the films reported in literature, depend on the network strain. The CTE of tensile films is smaller than that of their corresponding crystalline Semiconductors, but it is higher for compressive films. On the other hand, we found out that the elastic biaxial modulus of the Amorphous and metallic films is systematically smaller than that of their crystalline counterparts. This behavior stands for other films reported in the literature that were prepared by different techniques and deposition conditions. These differences were attributed to the reduction of the coordination number and to the presence of defects, such as voids and dangling bonds, in Amorphous films. On the other hand, columnar structure and microcrystallinity account for the reduced elasticity of the metallic films.