Optical properties of Zn-terminated ZnO bulk

Optical properties of ZnO bulk grown by hydrothermal method were investigated on the Zn-terminated surface by using Raman scattering and photoluminescence (PL). The typical Raman peak of E-2(high) mode was observed at 436.20 cm(-1). Also, the peak 576.20 cm-(1) was found to correspond to the LO phonon of A(1) mode. This peak was caused by the defects of O-vacancy, Zn-interstitial, or these complexes. The PL peak positions of B- and A-excitons are shifted to the shorter-wavelength side with decreasing temperature. The obtained PL intensity of excitons was exponentially reduced and the linewidth of the B-exciton broadened, with increasing temperature. This is thought to be the vibration mode of LO phonon, which may be participated in quenching process. Also, the empirical band gap was found to be E-g(T) = E-g(O) - alphaT(2)/(beta + T), where alpha and beta were turned out to be 5.70 x 10(-4) eV/K and 420 K, respectively. (C) 2003 Elsevier B.V. All rights reserved.