Analytical characterization of CuInS(2) semiconductor material

Systematic analytical procedures have been developed for determination of the stoichiometry of CuInS(2) and estimation of trace elements, including dopants and impurities, in the material. Samples of CuInS(2) are digested in an oxidizing acid to ensure completely transformation into Cu(2+), In(3+) and SO(4)(2-) ions. The stoichiometry determination is made sequentially by controlled potential electro-deposition of copper, followed by its EDTA titration, titrimetric determination of indium and gravimetric determination of sulphate, in a single sample solution. The relative errors for the determination of Cu and In are found to be -0.08% and +0.11% respectively, fulfilling the requirement for accurate stoichiometry assessment; that for S is -0.66%, which though rather high is still acceptable. For the determination of trace elements in CuInS(2), multistage combined procedures are employed. Cu in the sample solution is removed by electro-deposition and In by extraction of HInBr(4) with isopropyl ether, then most of the trace elements are finally determined by atomic-absorption spectrometry, and the rest by neutron-activation analysis. All the steps involved in the procedures have been optimized by using radioisotopes as tracers. By the procedures developed, a wide range of trace elements in CuInS(2), down to submicrogram level, can be determined.