Effect of annealing on the grain growth and luminescent properties of SrS : Cu blue phosphors

Systematic studies of the postgrowth annealing of molecular beam epitaxial deposited SrS:Cu films are reported. In the as-grown SrS: Cu films, the gra in size was small and the luminescence very weak. A step-annealing procedur e in a H2S atmosphere was developed and found to be a very efficient way to improve the crystallinity and luminescent properties without damage to the low temperature glass substrate and insulator layer of the device. A model is presented in terms of the free energy of formation and the reaction kin etics of Cu with H2S. It was proposed that the weak luminescence in the as- grown films was attributed to Cu atoms segregated at the grain boundaries i n the SrS film. The oxidation of atomic Cu by H2S and the diffusion of Cuinto the SrS lattice during annealing were responsible for the grain growth and the improved luminescent properties. (C) 1999 American Institute of Ph ysics. [S0021-8979(99)04708-8].