Effect of substrate orientation on CdS homoepitaxy by molecular dynamics.

CdS homoepitaxy growth was performed by molecular dynamics using different substrate orientations and structures in order to analyze the CdS crystallinity. As anticipated from thermodynamics of homoepitaxy, highly crystalline films with only point defects were obtained on substrates with rectangular surface geometries, including [ 11 2 ¯ ] zinc blende (ZB), [ 10 1 ¯ 0 ] wurtzite (WZ), [ 11 2 ¯ 0 ] WZ, [ 110 ] ZB, [ 010 ] ZB, and [ 1 10 1 1 10 ] ZB. In contrast, films grown on substrates with hexagonal surface geometries, corresponding to the [ 0001 ] WZ and [ 111 ] ZB growth directions, showed structures with a large number of defects including; anti-sites, vacancies, stacking faults, twinning, and polytypism. WZ and ZB transitions and grain boundaries are identified using a lattice identification algorithm and represented graphically in a structural map. A dislocation analysis was performed to detect, identify, and quantify linear defects within the atomistic data. Systematic simulations using different temperatures, deposition rates, and substrate polarities were perform to analyze the trends of dislocation densities on [ 0001 ] WZ direction and showed persistent polytypism. The polytypism observed in the films grown on the substrates with hexagonal surface geometry is attributed to the similar formation energies of the WZ and ZB phases. [ABSTRACT FROM AUTHOR]