Real space information from fluctuation electron microscopy: applications to amorphoussilicon

Abstract

Ideal models of complex materials must satisfy all available information about the system.Generally, this information consists of experimental data, information implicit tosophisticated interatomic interactions and potentially other a priori information. By jointlyimposing first-principles or tight-binding information in conjunction with experimentaldata, we have developed a method: experimentally constrained molecular relaxation(ECMR) that uses all of the information available. We apply the method to model mediumrange order in amorphous silicon using fluctuation electron microscopy (FEM) data asexperimental information. The paracrystalline model of medium range order is examined,and a new model based on voids in amorphous silicon is proposed. Our worksuggests that films of amorphous silicon showing medium range order (in FEMexperiments) can be accurately represented by a continuous random network model withinhomogeneities consisting of ordered grains and voids dispersed in the network.