Photoluminescence characteristics of as-synthesized and annealed ZnS:Cu,Al nanocrystals

Tri Tuan Nguyen, Xuan Anh Trinh, Le Hung Nguyen and Thanh Huy Pham

Abstract

As-synthesized ZnS:Cu,Al nanocrystals with average size of 2–3 nm show abroad emission band peaking at 445 nm (blue) and a shoulder at around 540 nm (green). Annealing the nanocrystals in nitrogen gas results in a reduction in the intensity of the blue emission while enhancing the intensity of the green emission band. The maximum of the green emission is first redshifted to around 590 nm when the annealing temperature is increased to 400 °C, and later blueshifted to 564 and 500 nm for the samples annealed at 500 °C and 600 °C for 1 h, respectively. The lower phase-transition temperature (from zinc blende to wurtzite) and the donor–acceptor pair luminescence process in nanocrystals are discussed