Density functional simulations of structure and polymorphism in Ga/Sb films

Thin films of gallium/antimony alloys are promising candidates for phase change memories requiring rapid crystallization at high crystallization temperatures. Prominent examples are the stoichiometric form GaSb and alloys near the eutectic composition GaSb7, but little is known about their amorphous structures or the differences between the 'as-deposited' (AD) and 'melt-quenched' (MQ) forms. We have generated these structures using 528-atom density functional/molecular dynamics simulations, and we have studied in detail and compared structural parameters (pair distribution functions, structure factors, coordination numbers, bond and ring size distributions) and electronic properties (densities of states, bond orders) for all structures. There is good agreement with x-ray diffraction data from deposited films of GaSb, and there is evidence for Sb segregation in GaSb7.