XPS Se 3d peaks in Na-added Bridgman CuInSe2+x

XPS measurements were made on samples from multi-crystalized ingots grown from Bridgman melts, having a composition corresponding to the formula CuInSe_2+x, containing added quantities of elemental sodium or Na₂Se. Special attention was paid to the XPS peaks Se 3d, Na 1s and O 1s. In particular, two main Se 3d peaks were observed at binding energies of 54.5 and 59 eV. The first of these, previously assigned to ternary CuInSe₂, increased with etching depth from the ingot surface but was little affected by the presence of Na. However, the second peak only appeared when Na or Na₂Se had been added to the melt. The 59 eV peak also increased somewhat with contaminant oxygen content and was assigned tentatively to Na₂SeO₃.