Misfit Stress Relaxation Mechanism in GeO₂/Ge Systems: A Classical Molecular Simulation Study

Abstract

The stress relaxation mechanism at the GeO2/Ge interface is studied by means of classical molecular simulation employing empirical force-fields. In general, the chemistry in GeO2 is characterized by weaker bonds and softer bond angles than that in SiO2, which has been considered to lead to the relaxation of the GeO2 film on Ge substrate. However, Ge-O-Ge angle is stiffer than Si-O-Si angle, and has a narrower equilibrium angle of 133o than that of Si-O-Si of 144o. The present simulation results show that the narrow Ge-O-Ge bond contribute the reduction of the compressive stress in the GeO2 films. If the Ge-O-Ge bond angle had the same equilibrium angle with Si-O-Si angle, a higher residual stress would remain in the GeO2 films.

Phonon Dispersion in 〈100〉 Si Nanowire Covered with SiO2Film Calculated by Molecular Dynamics Simulation

“…31,32 The difference in overestimation between ESW and SW potential function is attributed to the parameter sets of the potential functions. In the ESW potential, three-body parameters for Si-Si-Si triplet are set to be higher than those of the original SW potential in order to reproduce more precisely the bond bending energies, 22,23 resulting that the ESW potential function shows the higher phonon energies. In this study, however, since we focus on the effects of the presence of SiO 2 layer on the phonon energy dispersion, the results of bulk Si (Fig.…”

“…The MD simulations on the Si/SiO 2 systems are carried out using an interatomic potential function for Si, O mixed systems. 22,23 The potential is an extended version of the SW potential for pure Si systems, 15 which is defined by the sum of two-and three-body potential energy terms that depend on local environments. All parameters in the potential function were determined to reproduce deformation energies of small cluster models by the ab-initio molecular orbital calculations.…”

“…In this work, we investigate the phonon energy dispersions in SiNWs covered with thin SiO 2 films. We have performed a series of molecular dynamics simulation employing our developed interatomic potential for Si-O mixed systems, 22,23 and conducted the Fourier transform of the MD data to extract the phonon dispersion relation and the vibrational density of states.…”

“…It has the same length along 100 direction as the NW models, and consists of 960 Si atoms. Three-dimensional periodic boundary condition is adopted, i.e., the system is replicated throughout space to an infinite lattice.The MD simulations on the Si/SiO 2 systems are carried out using an interatomic potential function for Si, O mixed systems 22,23. The potential is an extended version of the SW potential for pure Si systems,15 which is defined by the sum of two-and three-body potential energy terms that depend on local environments.…”

Structural model for the GeO2/Ge interface: A first-principles study

“…We concluded that the flexibility of the O-Ge-O bonds contributes to the relaxation of interface stress, resulting in a GeO 2 /Ge interface that is superior to the SiO 2 /Si one. Watanabe et al claimed, using the classical molecular-dynamics simulation, that the narrow equilibrium Ge-O-Ge bond angles contribute to the reduction in compressive stress in GeO 2 films as well as flexible O-Ge-O bonds [10]. Although a considerable number of first-principles studies on the GeO 2 /Ge interface have been conducted based on the calculations on SiO 2 /Si interfaces [7,[11][12][13][14][15], the atomic and electronic structures of the GeO 2 /Ge interface have not been identified experimentally because GeO 2 is both water-soluble and thermally unstable at elevated temperatures.…”