Properties of cadmium sulphide films grown by single-source metalorganic chemical vapour deposition with dithiocarbamate precursors

CdS films were grown by MOCVD using dialkyldithiocarbamate precursors. A novel precursor Cd(S(2)CNMe(n)Bu)(2), more volatile than the simpler diethyldithiocarbamate was employed in most growth experiments, much earlier work being re-investigated in this study. CdS films were characterised by optical spectrophotometry, thickness determinations, X-ray diffraction, scanning electron microscopy, and electrical measurements. Both precursors gave similar results in film growth on glass substrates over 2 h at 450 and 500 degrees C. Films deposited on glass at 500 degrees C have mean thicknesses in the range 150-700 nm, columnar microstructures, and consist of hexagonal CdS with very pronounced, uniaxial (0001)-orientation. Electrical properties are consistent with trap-dominated behaviour, as evidenced by small photo-induced conductivity enhancements and hysteretic current-voltage characteristics. Typical resistivities at 40 degrees C are similar to 4 x 10(4) Omega . cm in the dark and similar to 6 x 10(3) Omega . cm under illumination. Epitaxial CdS film growth on InP substrates was examined, using Cd(S(2)CNMe(n)Bu)(2) as the precursor. A film grown on InP (111)P at 500 degrees C was characterised using a three-axis X-ray diffractometer. These measurements indicated triaxial orientation described by the relationships CdS (0001)parallel to InP (111) and CdS [<10(1)over bar 0>]parallel to InP [11(2) over bar].