Generation of extremely photo-luminescent CuBr crystallites in the CuCl/KBr system (CuCl film on KBr crystal)

The behavior of thermally-induced generation of extremely photo-luminescent CuBr crystallites in the previously reported CuCl/KBr system has been investigated by in situ optical absorption and photoluminescence (PL) spectroscopy. Upon suitable annealing of the system, CuCl can be fully changed into CuBr characterized by extremely-high-intensity PL. The PL spectrum is generally composed of three emission bands due to free-exciton, bound-exciton and defect-related emissions, with their intensity ratio depending on the annealing history. For a suitably-annealed system, in which the bound-exciton emission is maximized and the defect-related one is minimized at 17 K, extremely-high-intensity free-exciton PL is observed at room temperature. The integrated intensity of the room temperature free-exciton PL is similar to 10(3) times larger than that of CuCl, despite the general recognition that PL from CuBr is much weaker than that from CuCl. (c) 2007 Elsevier B.V. All rights reserved.