Photoluminescence study of ZnO nanowires grown by thermal evaporation on pulsed laser deposited ZnO buffer layer

The ZnO nanowires are grown by thermal evaporation on pulsed laser deposited ZnO buffer layer on silicon. Photoluminescence of ZnO nanowires is studied at various temperatures in the range from 6 K to room temperature and varying excitation intensities. At 6 K, the photoluminescence profile of ZnO nanowires shows bound exciton, free excitons (FXAn=1,FXAn=2), longitudinal optical phonon replicas (FXAn=1-mLO, m=1, 2, 3) of free exciton (FXAn=1), and donor acceptor pairs. The first longitudinal optical phonon replica (FXAn=1-1LO) dominates at room temperature. Photoluminescence peak shifts by 47 meV from free exciton energy with the increase in temperature to room temperature.