Structural and stimulated emission characteristics of diameter-controlled ZnO nanowires using buffer structure

Abstract

The diameter of ZnO nanowires grown by chemical vapour deposition was controlled by employing CrN buffer structures on the c-Al(2)O(3) substrate. The nanosized CrN islands with different morphologies were prepared by nitridation of thickness-controlled Cr film in NH(3) atmosphere. The ZnO nanowires grew normal to the surface of the CrN/c-Al(2)O(3) templates due to reduction in the lattice mismatch between ZnO and c-Al(2)O(3) by the CrN buffer layer. Investigation of the interface between CrN and ZnO by high resolution transmission electron microscopy revealed the presence of reactive layers such as ZnCr(2)O(4) and Cr(2)O(3). The diameter of nanowires significantly affected their stimulated emission characteristics. At room temperature, the threshold intensity for stimulated emission increased from 35 to above 500kW cm(-2) as the diameter of ZnO nanowires decreases from 223 to 77 nm. This dependence of threshold intensity for stimulated emission from nanowires is caused by an increase in the surface recombination and/or enhanced leakage of optical field in narrower nanowires.