Electrical and spectroscopic properties of amorphous copper sulfide films treated with iodine, lithium iodide and sodium iodide

Chemical modification of amorphous CuS films supported on polyethylene subs trate was performed by treatment with I-2, LiI and NaI in organic solvents. The electrical conductivities of the resulting films exhibited a metal-lik e temperature dependence down to approximate to 120 K, while the untreated films had a resistance minimum at approximate to 250 K. The X-ray photoelec tron spectra showed that the copper atoms were in the Cu(I) state in all of the materials studied. Upon treatment with I-2, a major part of CuS was co nverted to CuI, and the co-existence of two chemical species enhanced elect rical conduction. In films treated with LiI in acetone, the alkali metal io n was involved in a quasi-stoichiometric manner. The amorphous CuS was chem ically active and its chemical modifications gave new materials. (C) 2000 E lsevier Science S.A. All rights reserved.