Global transition path search for dislocation formation in Ge on Si(001)

Maras, Émile; Trushin, Oleg; Stukowski, Alexander; Ala-Nissilä, Tapio; Jónsson, Hannes

doi:10.1016/j.cpc.2016.04.001

Cited by 352 publications

(155 citation statements)

References 62 publications

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“…Lower panel: vibrational density of states calculated (solid line) and measured [37] (gray shaded area). been extended to systems where the atoms ideally have fourfold coordination [36]. There, the analysis is carried out for second nearest neighbors rather than first nearest neighbors.…”

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confidence: 99%

Optimal atomic structure of amorphous silicon obtained from density functional theory calculations

2017

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Atomic structure of amorphous silicon consistent with several reported experimental measurements has been obtained from annealing simulations using electron density functional theory calculations and a systematic removal of weakly bound atoms. The excess energy and density with respect to the crystal are well reproduced in addition to radial distribution function, angular distribution functions, and vibrational density of states. No atom in the optimal configuration is locally in a crystalline environment as deduced by ring analysis and common neighbor analysis, but coordination defects are present at a level of 1%-2%. The simulated samples provide structural models of this archetypal disordered covalent material without preconceived notion of the atomic ordering or fitting to experimental data.Amorphous silicon (a-Si) is the archetypal disordered covalently bonded material. It is also widely used for industrial purposes, with numerous applications in electronics and photovoltaics. Both aspects have triggered an intense research activity during the last few decades. a-Si can be obtained using several preparation techniques, including ion implantation, laser melting followed by fast quenching, various growth methods, and indentation [1][2][3][4][5][6]. The characteristics of the a-Si samples depend on the preparation method [7]. For example, vapor deposition often gives samples that include voids. Also, a-Si obtained by ion implantation tends to include a significant amount of coordination defects. But, annealing of the various types of samples seems to bring them closer to some common, ideal a-Si structure. The nature of this state is, however, a matter of long standing controversy. In addition to gaining an understanding of the basic characteristics of covalently bonded disordered networks, good structural models are an important prerequisite for theoretical investigations of the electronic and mechanical properties of such materials [8].Several different procedures have been proposed to generate realistic atomic scale models of a-Si. One approach is to generate a continuous random network (CRN) which can be built using various algorithms to give a structure with only 4-fold coordinated atoms, i.e. containing no coordination defects [9][10][11]. Another structural model involves nanoscopic crystal grains embedded in a disordered matrix. Arguments in favor of the latter have recently been presented in connection with an analysis of ion implantation samples [5,12]. Finally, constraints derived from experimental data have been used to guide the construction of a-Si models [13][14][15].Most of the proposed models have been able to reproduce well some of the measured structural features such as the radial distribution function (RDF) and bond angle distributions. The RDF, however, cannot discriminate between the various topological networks [12], and detailed information about the angular distributions is hard to obtain from experiments. To progress further in the search for an optimal a-Si model, Drabold recently pro...

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confidence: 99%

Optimal atomic structure of amorphous silicon obtained from density functional theory calculations

2017

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“…The visualization is realized using the open visualization tool (OVITO) [32]. Identify diamond structure (IDS) [33] in OVITO is used to identify the atoms arranged in hexagonal (wurtzite) or cubic diamond (zinc blende) lattice. The algorithm analyzes the local environment of each atom up to the second neighbor shell to determine the local structural type.…”

Section: Analysis Methodsmentioning

confidence: 99%

Effect of Substrate Surface on Deposition of AlGaN: A Molecular Dynamics Simulation

et al. 2018

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The growth of AlGaN has been extensively studied, but corresponding research related to the effect of AlN substrate surface has rarely been reported in literature. In this article, the effects of AlN substrate surface on deposition of AlGaN films were investigated by molecular dynamics (MD) simulations. (0001) Al-terminated and 0001 N-terminated AlN were considered as substrates. The quality of surface morphology and atomic scale structure of deposited AlGaN film are discussed in detail. The results show that the surface morphology and crystal quality of AlGaN film grown on (0001) Al-terminated AlN surface are better than for that grown on 0001 N-terminated AlN surface under various growing temperatures and Al/Ga injection ratios between Al and Ga. This can be attributed to the higher mobility of Al and Ga adatoms on the (0001) Al-terminated AlN surface. These findings can provide guidance for the preparation of high-quality AlGaN thin films on AlN substrate.

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“…faults [35]. In order to display more clearly the defect region, the atoms with diamond structure are removed, and the local lattice structure is indicated by color: the cubic diamond structure (first neighbor) is in red, the cubic diamond structure (second neighbor) in blue, the hexagonal diamond structure in yellow, and the others in white.…”

Section: Simulation Detailsmentioning

confidence: 99%