ABSTRACT
Chemical deposition (CD) of films is not a new technique. As early as 1835, Liebig reported the first deposition of silver-the silver mirror deposition-using a chemical solution technique [1]. The first reported CD of a compound semiconductor film appears to be formation of “lüsterfarben” (lustrous colors) on various metals from thiosulphate solutions of lead acetate, copper sulphate, and antimony tartrate, giving films of PbS, Cu-S or Sb-S, which possessed “splendid” colors (interference colors resulting from various thicknesses of the deposited films) [2]. More “recent” studies of this general process have invoked an electrochemical mechanism for some thiosulphate depositions, based on the dependence of deposition on either the nature (standard electrochemical potential) of the metal substrate or on a contacting non-noble metal (which can be looked at as an internal electrochemical deposition) [3-5]. However, while it is probable that an electrochemical or mixed electrochemical/chemical mechanism may be applicable on some metal substrates, some of these depositions do appear to be true CD processes. PbS is probably the clearest of these; others were Cu2S, Ag-S, Bi-S, Sb-S. Fe, Ni, and Co all formed apparent sulphide films on Fe substrates, while ammonium molybdate deposited a film from a thiosulphate solution that did not contain S and was probably an oxide. Beutel and Kutzelnigg cover a wide range of depo-
sitions from thiosulphate solutions-both CD and electrochemical [5]. Only in a few cases were these films characterized other than by color.
