Deposition of thin films of HgS from colloidal solutions

Abstract A method using colloidal solutions of HgS (created by means of two types of reactions) has been developed for depositing thin films of HgS, one of the few materials displaying “anomalous photoconductivity”. The most useful compositions of the solutions were found. The surface of very thin HgS films (up to about 0.7 μm) shows a pronounced roughness in the form of spheroids, while the underlying layers constitute a compact body. At a thickness of about 1 μm the surface becomes fairly smooth so that a reliable and unambiguously defined film thickness can be measured directly. At small thicknesses measurement of light absorption was used for an indirect evaluation of thickness. The effect of temperature on the growth rate is complicated and varies depending on the other conditions ( e.g. the concentrations of the solution components etc.) Except for the initial stage of growth (when the specific influence of the substrate material is felt) the thickness-time dependence is best approximated by a linear law. After about 24 h of deposition the depletion of the colloidal solution (because of coagulation) causes distortions in this law and the growth rate decreases markedly.