Atomic-scale disproportionation in amorphous silicon monoxide.

Akihiko Hirata,Shinji Kohara,Toshihiro Asada,Mingwei Chen,Chihiro Yogi,Takeshi Fujita,Masazumi Arao,Yongwen Tan,Hideto Imai

doi:10.1038/ncomms11591

Abstract

Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

Highlights

Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications
It has been long known that the heat of combustion of amorphous Silicon monoxide (SiO) is significantly higher than that of an equilibrium mixture of amorphous Si and SiO2 and, importantly, the X-ray diffraction (XRD) patterns of amorphous SiO cannot be interpreted by the summation of amorphous Si and SiO2 spectra[10]
In this study we employ our recently developed angstrom-beam electron diffraction (ABED) method[23,24] to investigate the local structure of amorphous SiO, which is supplemented by synchrotron high-energy XRD (HEXRD) and computational simulations based on molecular dynamics (MD) and reverse Monte Carlo (RMC) calculations

Summary

Introduction

Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrombeam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. We develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. In this study we employ our recently developed angstrom-beam electron diffraction (ABED) method[23,24] to investigate the local structure of amorphous SiO, which is supplemented by synchrotron high-energy XRD (HEXRD) and computational simulations based on molecular dynamics (MD) and reverse Monte Carlo (RMC) calculations. On the basis of ABED and HEXRD experiments, we develop a heterostructure model of the disproportionated amorphous SiO which well explains the structure and properties of the amorphous material

Methods

Results

Conclusion