Optical properties of ZnO crystals containing internal strains

The way in which in-grown strain impacts the optical properties of crystals can be revealed when combined with annealing studies. During the annealing process strains may be relieved, and when they are, the intrinsic energy b ands adjust to these changes. These changes are readily detected by reflect ion measurements. Energy changes in the intrinsic bands may also be reflect ed in the extrinsic optical transitions. In this paper we show how stress c hanges during the annealing process can be used to develop a model that exp lains the origin of emission lines at 3.2898 and 3.2176 eV. (C) 1999 Elsevi er Science B.V. All rights reserved.