Structural and optical properties of Cu implanted Ge thin films

Effects of rapid thermal annealing (RTA) on 100 keV Cu implanted germanium (Ge) thin films were studied in the present report. The Cu ion implantation into Ge films was carried out at different ion fluences 5 x 1015 and 1 x 1016 ions/cm2. Subsequently, the implanted samples were subjected to RTA at 600 degrees C. XRD and Raman results illustrate the amorphization of implanted films, whereas RTA results in crystallization. Crystallite size increases from 10.5 to 11.6 nm with fluence for RTA-treated samples. The bandgap of pristine film is 0.73 eV, which gets narrowed to 0.59 eV with an increase in ion fluence. RTA leads to increase in band gap up to 1.16 eV due to recovery of lattice damage and recrystallization of films. XPS analysis of RTA-treated implanted films reveals the presence of Ge, Ge suboxides, and Cu. The broad PL emission in the visible region signifies the possible use of Ge for optoelectronic applications.