Enhanced near-band-edge emission from a-plane ZnO thin films on SrTiO3 substrates

Epitaxial ZnO with controlled orientations is highly concerned, and we report epitaxial growth of (0001)- and (11-20)-oriented ZnO films, respectively, on (111)- and (100)-SrTiO3 (STO) substrates using pulsed laser deposition. The epitaxial growth of (11-20)-ZnO films on (100)-STO, with in-plane orientation relationship of ZnO [0001]//STO [110] and ZnO [10-10]//STO [1-10], is realized. It is revealed that the (11-20)-ZnO films have much stronger photo-luminescence (PL) intensity than those of the (0001)-oriented ones, while the electric conductance remains comparable with the latter. The electrical and PL properties of the (11-20)-ZnO films are correlated with the in-plane polarity.