In order to tune the carrier concentrations, Cu-rich Cu2+x
Se targets (x=0, 0.01, 0.03, 0.05, 0.1, 0.3) were prepared by a solid-state reaction method . Cu2-y
Se thin films were grown on (110)-oriented LSAT (a=b=c=3.868Å) single-crystalline substrates by pulsed laser deposition, using a KrF excimer laser (248nm, Lamda Physik COMPexPro 201). Film deposition has been carried out on the substrate at 600 degC under 0.5Pa argon pressure with a subsequent in situ annealing process at 600 degC for 30min. The laser energy intensity and repetition rate were about 6J/cm2 and 5Hz, respectively. The base pressure of the chamber was about 2×10−4
Pa.