Chemical vapour deposition of copper(I) iodide on c-plane sapphire using ethyl iodide and 2-iodo-2-methylpropane

Abstract

In this paper, we report the deposition of copper(I) iodide (CuI) on c-plane sapphire by chemical vapour deposition (CVD). Single crystals of $\gamma$-CuI with an out-of-plane orientation of 111, as determined by X-ray diffraction, were grown on the substrate. The copper precursor used was bis(N,N’-di-sec-butylacetamidinato) dicopper(I). Two different iodine precursors, ethyl iodide (EtI) and 2-iodo-2-methylpropane (^tBuI), are discussed in detail. X-ray diffraction and laser scanning microscopy images show the influence of precursor and growth conditions on the morphology and growth rate of CuI. Using ^tBuI the growth temperature could be lowered and the formation of crystals with flat hexagonal and trigonal shape could be observed. At growth temperatures T_growth $\le$ 230 °C, another CuI phase in addition to $\gamma$-CuI is observed by X-ray diffraction. Photoluminescence measurements show a sharp peak at 380 nm (3.26 eV) that can be assigned to bound excitons of the other CuI phase.