Strain, luminescence, and electrical properties of $Zn_{1-x}Mn_xS$ nanocrystalline films prepared on silicon wafers

Abstract

Nanocrystalline $Zn_{1−x}Mn_xS$ films (0 \leq x \leq 0.25) were deposited on silicon wafers at 473 K using a simple resistive thermal evaporation technique. Morphological and structural measurements revealed that all the films investigated were nanocrystalline with a cubic structure. The lattice parameter increased linearly with Mn concentration. The surface roughness of all the films was shown to be in the range 1.2–3.5 nm. A blueshift in the photoluminescence was observed in the films with increasing Mn concentration along with an intense ultraviolet emission and orange-yellow emission, which are ascribed to the quantum confinement effect. The composition had a significant influence on the orange-yellow emission intensity as well as peak positions. The excitation wavelength of all the samples was 330 nm and emission wavelengths were observed around 410–560 nm. The presence of many recombination sites, surface areas, and defect types leads to broad band photoluminescence emission lines instead of sharp bands. The electrical resistivity as well as activation energy decreased with increasing Mn concentration