Electronically designed amorphous carbon and silicon

Prasai, K.; Biswas, Parthapratim; Drabold, D. A.

doi:10.1002/pssa.201532973

Cited by 12 publications

(9 citation statements)

References 42 publications

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“…al. and others 36,37 have used electronic information to aid in modeling amorphous system. Conversely, EDOS obtained for our models validate accuracy of our models.…”

Section: B Electronic Propertiesmentioning

confidence: 99%

Large and realistic models of amorphous silicon

Igram

Bhattarai

Biswas

et al. 2018

Journal of Non-Crystalline Solids

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Amorphous silicon (a-Si) models are analyzed for structural, electronic and vibrational characteristics. Several models of various sizes have been computationally fabricated for this analysis. It is shown that a recently developed structural modeling algorithm known as force-enhanced atomic refinement (FEAR) provides results in agreement with experimental neutron and x-ray diffraction data while producing a total energy below conventional schemes. We also show that a large model (∼ 500 atoms) and a complete basis is necessary to properly describe vibrational and thermal properties. We compute the density for a-Si, and compare with experimental results.

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“…al. and others 36,37 have used electronic information to aid in modeling amorphous system. Conversely, EDOS obtained for our models validate accuracy of our models.…”

Section: B Electronic Propertiesmentioning

confidence: 99%

Large and realistic models of amorphous silicon

Igram

Bhattarai

Biswas

et al. 2018

Journal of Non-Crystalline Solids

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“…To understand the electronic structure of the models, we examine the total density of states (DoS), partial DoS and inverse participation ratio (IPR). These calculations not only help us check the validity of the model, but can also be used for a priori information to model amorphous materials 27,28 . The plot of the DoS in Fig.…”

Section: B Electronic Propertiesmentioning

confidence: 99%

Structure and charge transport of amorphous $Cu$-doped $Ta_2O_5$ : An ab initio study

Thapa,

Bhattarai,

Kozicki

et al. 2020

Preprint

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In this paper, we present ab initio computer models of Cu -doped amorphous T a2O5 , a promising candidate for Conducting Bridge Random Access Memory (CBRAM) memory devices, and study the structural, electronic, charge transport and vibrational properties based on plane-wave density functional methods. We offer an atomistic picture of the process of phase segregation/separation between Cu and T a2O5 subnetworks. Electronic calculations show that the models are conducting with extended Kohn-Sham orbitals around the Fermi level. In addition to that, we also characterize the electronic transport using the Kubo-Greenwood formula modified suitably to calculate the space-projected conductivity (SPC) 1 . Our SPC calculations show that Cu clusters and under-coordinated T a adjoining the Cu are the conduction-active parts of the network. We also report information about the dependence of the electrical conductivity on the connectivity of the Cu submatrix. Vibrational calculations for one of the models has been undertaken with an emphasis on localization and animation of representative modes.

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“…This has produced models that have remarkably fewer defects in the model. For more on the calculations, please refer to [32,75].…”

Section: Bsmentioning

confidence: 99%

Electrons and phonons in amorphous semiconductors

Prasai

Biswas

Drabold

2016

Semicond. Sci. Technol.

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The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using current tools of a first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon (a-Si), amorphous selenium (a-Se) and amorphous gallium nitride (a-GaN). In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally induced fluctuations in energy eigenvalues obtained from the density-functional theory (i.e. Kohn-Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of a-GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous examples. Next, we explore the consequences of changing the charge state of a system as a proxy for tracking photoinduced structural changes in the materials. Where transport is concerned, we lend insight into the Meyer-Neldel compensation rule and discuss a thermally averaged Kubo-Greenwood formula as a means to estimate electrical conductivity and especially its temperature dependence. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann-Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify a low-energy amorphous phase of silicon including several coordination defects, yet with a gap close to that of good quality a-Si models.

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Electronically designed amorphous carbon and silicon

Cited by 12 publications

References 42 publications

Large and realistic models of amorphous silicon

Large and realistic models of amorphous silicon

Structure and charge transport of amorphous $Cu$-doped $Ta_2O_5$ : An ab initio study

Electrons and phonons in amorphous semiconductors

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