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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Gallium-antimony (GaSb) alloys are crucial for phase change memories due to their rapid crystallization at high temperatures.
• Understanding the amorphous structures of GaSb and its alloys, specifically 'as-deposited' (AD) and 'melt-quenched' (MQ) forms, is vital for optimizing memory performance.
• Limited knowledge exists regarding the structural and electronic differences between AD and MQ amorphous GaSb and related alloys.

Purpose of the Study:

• To generate and compare the amorphous structures of stoichiometric GaSb and eutectic GaSb(7) in both as-deposited (AD) and melt-quenched (MQ) forms.
• To investigate the detailed structural parameters, including pair distribution functions, coordination numbers, and ring size distributions.
• To analyze the electronic properties, such as densities of states and bond orders, for these amorphous structures.

Main Methods:

• Utilized 528-atom density functional/molecular dynamics simulations to generate amorphous structures.
• Performed detailed comparative analysis of structural parameters (pair distribution functions, structure factors, coordination numbers, bond and ring size distributions).
• Evaluated electronic properties, including densities of states and bond orders.

Main Results:

• Generated and characterized amorphous structures for GaSb and GaSb(7) in both AD and MQ states.
• Observed good agreement between simulated structural data and experimental X-ray diffraction results for deposited GaSb films.
• Identified distinct structural and electronic differences between AD and MQ forms, with evidence of Sb segregation in GaSb(7).

Conclusions:

• The study provides a detailed understanding of the amorphous structures and electronic properties of GaSb and GaSb(7) alloys.
• Simulation results align with experimental data, validating the computational approach for studying these materials.
• Findings offer insights into material design for advanced phase change memory applications by elucidating structural differences.