Island formation at the initial stages of epitaxial ZnS films grown by single source chemical vapor deposition

Chemical vapor deposition of single-source precursor zinc diethyldithiocarbamate Zn[S₂CN(C₂H₅)₂]₂ and subsequent decomposition on heated Si(111) has been shown to produce epitaxial ZnS films. During the initial growth studies, X-ray photoemission spectroscopy indicated a relatively high concentration of carbon at the interface, which decreased with increasing film thickness. The interfacial carbon is attributed to chemisorption of byproducts during precursor decomposition. The higher than expected binding energy of Zn 2p3/2 for the ultrathin films (~5 Å) approached the bulk ZnS value as film thickness increased (~2000 Å). This was ascribed to changes in crystallite size, which resulted in different core-hole screenings. The combined results are related to a kinetic process in which various carbon-terminated sites on Si(111) surface inhibited the two-dimensional coalescence of ZnS clusters. The films were initially grown via formation of epitaxial three-dimensional islands. Our results suggest that while the precursor chemistry and associated byproduct concentration can significantly influence the growth mechanism, the epitaxial driving force is sufficiently strong to overcome such chemical defects at the interface.