Thermal annealing effects on ZnO films grown on graphene buffered Si substrates

ZnO films deposited on SiO2/Si substrate with a graphene single layer (GSL) were studied by using an ultra-high vacuum sputter. The as-prepared films were annealed at temperature ranges from 500 degrees C to 800 degrees C for 1 min under ambient N2 gas. When the annealing temperature was increased up to 800 degrees C, the root mean square roughness of the ZnO/Si sample surface decreased down to 3.4 nm, and the grain sizes increased about 50.8 nm with a clear grain boundary. From the photoluminescence (PL) spectra, the high intensity of near-band-edge UV emission at 380 nm (3.26 eV) and the broad band emission between 450 and 650 nm, known as the visible defect related PL band, decreased with increasing annealing temperature up to 800 degrees C. The ZnO thin films on the growth on the GSL and post-annealing at 700 degrees C for 1 min under ambient N2 gas had the best structural and optical properties.