CdS and ZnS thin films were grown by an MOCVD method, using as the initial film-forming substance the vapour of chelate OMCs of ML₂-type, where: M is a metal, L is a ligand. Such chelate OMCs are, basically, either Cd- or Zn-diethildithiocarbomate. They have significant volatility and form the sulphides of corresponding metals under thermal heating of more than 300°C.

Deposition was carried out in a vertical quartz reactor in a quasi closed volume on a silicon substrate, with (100) orientation heated by a resistive heater. Thickness was checked by the interference method and was 0.5-1.5 µm.

Stoichiometry, film composition and homogeneity with depth were studied by the method of High Vacuum Thermal Mass spectrometry. Quantitative and qualitative data were obtained on desorption processes of components evaporating from the surface of samples by means of an Isotope Induction Mass-spectrometer Ml-1201 (USSR). The resolution of this system was more than 5000 amu. The sensitivity was greater than 10¹⁰ sec^-1.

CdS and ZnS films were exposed to heating by the thermal resistive heater within a temperature range of 660 to 860 K. The spectrum composition of evaporation products and relationship of evaporation flow of metal (N_m) and non-metal (N_x) were analysed. In addition, the relationship of NS₂/NS evaporation was analysed. When beginning the measurements, the evaporation dynamics of atoms and molecules and their ratio at fixed temperature was recorded. These measurements were then repeated when changing the temperature of films during a short time interval. The relation between evaporation of film components CdS at T=700 K and ZnS at T=750 K during the 5 hours of annealing showed that N_m/N_x in this interval for CdS is equal to 1±0.015 and for ZnS film is equal to 1.01±0.018. This suggested that there is high stoichiometry and homogeneity of composition over practically the whole depth of these films. The ratio NS₂/NS was 9-10 for CdS films in contrast to 2-3 for evaporation ZnS films. When changing the temperature of CdS and ZnS films, the relation of N_m/N_x and NS₂/NS evaporation continued to be invariable.

These results are in agreement with electron theory for the desorption of binary semiconductor compounds in vacuum proposed previously in our laboratory. This indicates that not only is there the good stoichiometry of film composition, but also that electrons and holes are in equilibrium in relation to defect subsystems of the films under investigation.

The desorption activation energies of film components were found to be similar and accounted for 3±0.1eV for CdS film and 2.17±0.2eV for ZnS, which is 1.5-2 times large than for the corresponding crystals.

No added atoms, impurities were found among the CdS and ZnS film products of evaporation with in the instrument's relative sensitivity (higher than 0.005%).

The presence of microimpurities was analysed by methods of Time of Flight Massspectrometry with Laser Excitation of the Specimen (non-commercial device, vacuum 10^-9 Torr, mass registration 1-300 amu, resolution 300, sensitivity ~10^l6 sm^-3, depth of analysis ~1µm) and ICP-MS (non-commercial device). The following impurities were found: C ~7x10^l7 sm³, N ~2x10^l7 sm³, O ~l.1x10¹⁹ sm³.