Structure evolution in chemical vapor-deposited ZnS films

The evolution of the crystallographic structure of ZnS films (thickness approximate to 2 mum) grown on Si(100) wafers by the single-source chemical vapor deposition (CVD) of zinc dimethyldithiocarbamate precursor has been examined. X-ray and electron diffraction indicated that the films were cubic (sphalerite) and oriented preferentially along the (111) direction. Transmission electron microscopy (TEM) indicated that the films were composed of a uniformly distributed array of columns approximately 300-500 nm wide. High-resolution TEM at the interface showed that these columns were attached to the substrate surface via smaller columns (similar to50-100 nm wide). The density of crystallographic defects in the bulk columns was lower than that in the interfacial columns. Orientation of the crystallites occurred at a much earlier stage in film growth compared to theoretical predictions for evaporative deposited films, suggesting that the presence of impurities during chemical vapor deposition may influence the structural evolution of the film.