Influence of target to substrate distance on the sputtered CuCl film properties

CuCl is a potential candidate for UV optoelectronic devices due to its superior optical properties and lattice matching with Si. Stoichiometric CuCl thin films of polycrystalline nature were grown by RF magnetron sputtering technique. The effect of varying the target to substrate distance on the compositional, structural and optoelectronic properties of the sputtered films was analysed. A critical target to substrate distance (dts) was observed and the film properties were clearly different above and below this distance. Based on the film properties, the optimum spacing of dts = 6 cm was found to yield stoichiometric and high optical quality films. The existence of more than one chemical bonding state was identified in nonstoichiometric, chlorine rich, films by analysing the Cu 2p3/2 core level XPS spectra. Chlorine rich samples were found to show a noticeable emission from deep levels at ∼ 515 nm in cathodoluminescence (CL) spectroscopy. An exciton mediated sharp UV luminescence (385 nm) emission was realized at room temperature in the stoichiometric CuCl thin films.