Crystal structure and photoluminescence of ZnSe and ZnSe:Mn nanocrystals obtained by combustion synthesis

Abstract

ZnSe and ZnSe:Mn nanocrystals were obtained by combustion synthesis (self-propagating high-temperature synthesis) using current pulses to initiate a reaction with amplitudes of ∼35 A and ∼40 A. The magnitude of the amplitude of the current pulse affects the size of the nanocrystals, their phase composition, the ratio of the cubic and hexagonal phases, the degree of microstresses and the density of dislocations. The inclusion of Mn dopants into ZnSe has little effect on the nanocrystal morphology and strongly influences the morphology of polycrystals. An EPR spectrum of Mn2+ ions with a hyperfine structure constant A = 6.55 mТ and a g-factor g = 2.0055, which is due to Mn2+ ions in a cubic environment, was found in self-activated and doped ZnSe and ZnSe: Mn nanocrystals. It was found that increasing the amplitude of the current pulse, which initiates the combustion synthesis reaction, increases the intensity of the diffusion processes and more effective isovalent substitution of Zn2+ ions by Mn2+ ions in the crystal lattice of ZnSe nanocrystals. The photoluminescence spectra of ZnSe and ZnSe:Mn nanocrystals were investigated, and individual emission bands were detected in the integral spectra. There were three such individual bands in the photoluminescence spectrum of ZnSe nanocrystals. Their maxima were characterized using the following parameters: λ max = 592 nm (E = 2.095 eV), λ max = 543 nm (E = 2.282 eV), and λ max = 505 nm (E = 2.455 eV). Six individual emission bands were detected in the photoluminescence spectra of ZnSe:Mn nanocrystals with the parameters: λ max = 675. 5 nm (E = 1.835 eV), λ max = 642.5 nm (E = 1.929 eV), λ max = 613 nm (E = 2.022 eV), λ max = 583.5 nm (E = 2.124 eV), λ max = 550 nm (E = 2.255 eV), λ max = 528.5 nm (E = 2.345 eV). This paper discusses the nature of the centers of radiative recombination of individual bands.