XPS STUDY OF COPPER SULFIDES INSERTED INTO A LANGMUIR-BLODGETT MATRIX

X-ray photoelectron spectroscopy (XPS) is used to characterize copper sulphides inserted into Langmuir-Blodgett (LB) films of behenic acid. Comparisons are made between samples exhibiting very different electri cal conductivity but synthesized by the same method. Sulphur atoms wit h two different environments are found: divalent sulphur S2- and dimer sulphur (S2)2-, higher concentrations of dimer sulphur (S2)2- being p resent in insulating samples. Chemical bonding of copper in LB films i s compared with CuS and Cu2S powders. The copper to sulphur ratio and the divalent to dimer sulphur ratio are obtained from various samples and lead to the formula: Cu2S, xS2 with x ranging from 0.5 to 0.8.