Close space sublimation growth of single-phase CuI thin films: Evaluation of structural and electronic properties.

Binary metal halide, Copper iodide (CuI) is a versatile p-type transparent conductor that has been shown exceptional functionalities towards optoelectronic and thermoelectric applications. Properties such as transparency and conductivity are very sensitive to the morphology, and Cu and I defects. In this study, we report success in preparation of CuI thin films through cost effective close space flux sublimation of CuI powders in vapor transport tube furnace under the optimized pressure (10 mBar with N2 flow) and temperature (490 °C). As-deposited samples are found to show CuI phase along with fraction of Cu3N impurity phase. However, post iodization led to transformation into single phase CuI with subtle changes in lattice constant and Cu-I bond length, as revealed from X-ray diffraction and Raman spectroscopy. The bandgap of the thin film is estimated as 2.95 eV, and four-point electrical measurements show conducting behavior establishing the continuity of thin films. The success in CuI thin film preparation through close space sublimation could pave a way to prepare large area films at low cost. [ABSTRACT FROM AUTHOR]