Abstract
Variability in the short-to-intermediate range order of pure amorphous silicon prepared by different
experimental and computational techniques is probed by measuring mass density, atomic
coordination, bond-angle deviation, and dihedral angle deviation. It is found that there is significant
variability in order parameters at these length scales in this archetypal covalently bonded,
monoatomic system. This diversity strongly reflects preparation technique and thermal history in
both experimental and simulated systems. Experiment and simulation do not fully quantitatively
agree, partly due to differences in the way parameters are accessed. However, qualitative agreement
in the trends is identified. Relaxed forms of amorphous silicon closely resemble continuous
random networks generated by a hybrid method of bond-switching Monte Carlo and molecular
dynamics simulation. As-prepared ion implanted amorphous silicon can be adequately modeled
using a structure generated from amorphization via ion bombardement using energetic recoils.
Preparation methods which narrowly avoid crystallization such as experimental pressure-induced
amorphization or simulated melt-quenching result in inhomogeneous structures that contain regions
with significant variations in atomic ordering. Ad hoc simulated structures containing small
(1 nm) diamond cubic crystal inclusions were found to possess relatively high bond-angle deviations
and low dihedral angle deviations, a trend that could not be reconciled with any experimental
material.
