First-Principles Investigation of Low Energy<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>E</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math>Center Precursors in Amorphous Silica

Anderson, Nathan L.; Vedula, Ravi Pramod; Schultz, Peter A.; Ginhoven, Renée M. Van; Strachan, Alejandro

doi:10.1103/physrevlett.106.206402

Cited by 55 publications

(48 citation statements)

References 17 publications

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“…This large variability in the formation energies results from variability in local structure in the ensemble of structures and has been observed in other amorphous dielectrics. 37 To our knowledge this is the first report of defect formation energy in a-Si 3 N 4, so we compare our results to vacancy formation energy in crystalline Si 3 N 4 ploymorphs and point defects in a-SiO 2 . The heat of formation of the nitrogen vacancy in β-Si 3 N 4 was calculated to be 3.6 eV and formation energy for point defects in amorphous SiO 2 were predicted to vary between 1.7 eV and 6.8 eV.…”

Section: Distribution Of Defect Formation Energiesmentioning

confidence: 99%

“…[27][28][29][30][31][32][33][34][35][36] While structural, electronic, and vibrational properties based on these models have been extensively reported, comprehensive models capturing the effect of inherent local variability in the atomic structure and topological disorder of a-Si 3 N 4 are still lacking. Consequently, theoretical predictions of trap depths based on these models report few distinct levels in the band-gap, as opposed to a range of values as expected from the atomic variability of the amorphous network 37 and reported in recent TSCIS measurements. 26 In this paper, we generate and analyze an ensemble of well-equilibrated, statistically independent, a-Si 3 N 4 structures to characterize the effect of local variability on the structure, mechanical, and electronic properties.…”

Section: Introductionmentioning

confidence: 99%

“…The heat of formation of the nitrogen vacancy in β-Si 3 N 4 was calculated to be 3.6 eV and formation energy for point defects in amorphous SiO 2 were predicted to vary between 1.7 eV and 6.8 eV. 37 The lower defect formation energy in a-Si 3 N 4 relative to a-SiO 2 explains the comparatively high concentration of defects observed experimentally in a-Si 3 N 4 dielectrics compared to a-SiO 2 , a similar and more commonly used dielectric for electronic applications.…”

Section: Distribution Of Defect Formation Energiesmentioning

confidence: 99%

“…Similar approaches have been effectively used by other researchers for characterizing structural properties and defect formation energies in amorphous silica. [37][38][39][40] We use a combination of MD simulations with empirical potentials and ab initio structural relaxations to generate the ensemble of well equilibrated, stress-free stoichiometric a-Si 3 N 4 structures. Slow annealing via classical MD simulations followed by density functional theory (DFT) optimization leads to structures with small density of defects and several defect-free ones.…”

Section: Introductionmentioning

confidence: 99%

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Effect of topological disorder on structural, mechanical, and electronic properties of amorphous silicon nitride: An atomistic study

2012

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ABSTRACT:We present a first principles study of the effect of atomic variability on the structure, mechanical and electronic properties of amorphous silicon nitride. Using a combination of molecular dynamics and density functional theory calculations we predict an ensemble of statistically independent, well-relaxed and stress-free amorphous silicon nitride structures. We analyze the short, intermediate, and long-range order of the structures generated using radial distribution functions, ring statistics, bond angle distributions, and translational invariance parameters. Though energetically very similar, these structures span a wide range of densities (2.75-3.25 g/cm 3 ) and bulk moduli (115GPa to 220 GPa) in good agreement with the fabrication-dependent experimental range. Chemical bonds and atomic defects are identified via a combination of bond distance cutoff and maximally localized Wannier function analysis. A significant number of the amorphous structures generated (~30%) are defect-free providing an ideal reference to characterize the formation energy of the various point defects and their defect energy levels. An analysis of the Kohn-Sham density of states and energetics of the structures reveals that defects in amorphous dielectrics have a distribution of associated properties (e.g. formation energies and electronic energy levels) due to variations in local atomic structure; this should be taken into consideration in physics-based continuum models of these materials.

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Section: Distribution Of Defect Formation Energiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Distribution Of Defect Formation Energiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of topological disorder on structural, mechanical, and electronic properties of amorphous silicon nitride: An atomistic study

2012

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“…The simulation cells include a half-sphere of amorphous SiO 2 (the tip) 36 and a poly-(methyl-methacrylate) (PMMA) slab as shown in the snapshot in Figure 1. We use the LAMMPS MD package developed at Sandia National Laboratories 37 and the DREIDING force field to describe the interaction between atoms.…”

Section: Methodology a Computational Detailsmentioning

confidence: 99%

Molecular dynamic simulation of tip-polymer interaction in tapping-mode atomic force microscopy

Venturini

Strachan

2013

Journal of Applied Physics

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We present a molecular dynamic study of the interaction between an amorphous silica tip (SiO 2 ) and an amorphous poly-(methyl-methacrylate) substrate under conditions relevant for tapping-mode atomic force microscopy. To capture the actual dynamics of the tip, we use the dynamic contact simulation method [Kim et al., J. Appl. Phys. 112, 094325 (2012)]. We obtain force-displacement relationships both for neat polymer substrates and a sample with a sub-surface nanotube and extract the local stiffness and energy dissipation per cycle. The simulations capture non-trivial aspects of the interaction that originate from the viscoelastic nature of the polymer including an increase in repulsive interaction force during approach with tip velocity and an increase in adhesion during retraction with decreasing tip velocity. Scans of local stiffness and dissipation over the samples reveal intrinsic variability in the amorphous polymer but also the effect of local surface topography on the extracted properties as well as the ability of the method to detect a sub-surface nanotube. This insight and quantitative data should be valuable to interpret the results of atomic force microscopy studies. V C 2013 AIP Publishing LLC. [http://dx

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Silica, Silicate, and Aluminosilicate Glasses

Mahadevan¹,

Du²

2022

Atomistic Simulations of Glasses

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First-Principles Investigation of Low EnergyE′Center Precursors in Amorphous Silica

Cited by 55 publications

References 17 publications

Effect of topological disorder on structural, mechanical, and electronic properties of amorphous silicon nitride: An atomistic study

Effect of topological disorder on structural, mechanical, and electronic properties of amorphous silicon nitride: An atomistic study

Molecular dynamic simulation of tip-polymer interaction in tapping-mode atomic force microscopy

Silica, Silicate, and Aluminosilicate Glasses

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