Thermal evaporated Copper Iodide (CuI) thin films: A note on the disorder evaluated through the temperature dependent electrical properties

Copper Iodide (CuI) thin films are p-type transparent conductors. In the present investigation, the physical properties of thermally evaporated (at 300 K) γ-phase copper iodide (CuI) thin films (of thickness 120 nm) prepared on the quartz substrates have been reported. The grain size (from SEM measurements) is ~ 80 nm. The (direct) optical band gap of CuI is 3.0 eV; the films show >70% transmission in the wavelength range 550–1000 nm and have low electrical resistance 72 mΩ cm. The Photo-luminescence spectra (with excitation wavelength 325 nm) shows a violet emission at ~ 409.4 nm (corresponds to the near band edge emission) and a shoulder peak centered at 417.4 nm (indicates the trap level near to the valence band edge induced by Iodine). The Hall mobility and carrier density of holes (from room temperature Hall measurements) in CuI thin films calculated are 1.46 cm2/V/s and 5.8×1019 cm−3 respectively. The disorder in the CuI thin films is evaluated by the temperature dependent (20–300 K) electrical resistivity measurements. The surface work-function of the CuI thin films measured by Kelvin probe technique; a non-destructive and sensitive surface analytical technique, is 4.71 eV (with reference to the gold probe).