Copper oxy-sulfide and copper sulfate thin films as transparent p-type conductive electrodes.

Starting from evaporated Cu layers, oxidation and sulfurization processes were developed by reaction at 250 °C with O 2 or elemental sulfur to obtain Cu 2 O and CuS thin films, respectively, with p-type conductivity and visible transparency. With the aim of achieving mixed compounds that combine the best properties of oxides (transparency) and sulfides (metal-like conductivity), different methods were tested, including Cu 2 O sulfurization, CuS oxidation and direct Cu sulfoxidation. The crystalline structure, morphology and optical and electrical characteristics of the various samples were studied comparatively. CuSO 4 crystals with a mean size above 40 nm were obtained by sulfoxidation, showing higher transmittance and lower resistance than the Cu 2 O film shaped by crystallites of ∼13 nm. Moreover, a superior electrode quality was achieved after CuS oxidation, which produces a mixture of small Cu 2 O and larger Cu 2 S nanocrystals with visible transmittance as high as the pure oxide and a hole density close to the sulfide. [ABSTRACT FROM AUTHOR]