Structural and optical properties of Zn₃P₂ thin films

Abstract

Conditions have been developed for the deposition of a stoichiometric thin film of zinc phosphide (Zn₃P₂) using electron beam evaporation. Structural properties of as-deposited and annealed thin films of zinc phosphide have been studied using electron and X-ray diffraction. The as-deposited film is non-crystalline, structural ordering starts on annealing at 200° C and the film becomes crystalline at 300° C with the structure matching that of the bulk material. Optical absorption has been investigated over the range 1 to 3 eV with emphasis on the region of interband absorption. The thin film absorption edge is found to be exponential for lower values of absorption coefficient. Analysis of thin film data showed that Zn₃P₂ is a direct-band-gap material. On annealing there is a shift in the band edge towards higher energy.