Solution-processed NiS thin films: structural, morphological, compositional and optical analysis

Abstract

The present work elucidates a study on the synthesis and characterization of nanostructured NiS thin films, an optical absorber material. NiS films have been deposited on glass substrates using a simple and cost-effective chemical solution route. The deposition process has been accomplished using an aqueous solution of nickel chloride, thiourea, ammonia and Triton. As-deposited and thermally annealed films have been characterized using X-ray diffractometry, Fourier transform infrared spectrometry, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, and UV–visible spectrometry. It has been observed that the deposited films are nanocrystalline in nature and belong to the rhombohedral structure of the millerite phase. The diffraction peaks become more sharp, discrete and intense whereas the crystallite size increases from 9.89 to 11.78 nm with annealing treatment. Some variations in the infrared peaks have been observed with annealing. The characteristic peak for Ni–S vibration has been observed at ∼604 cm−1. The surface of the films is smooth, uniform, and free from cracks and pinholes. The optical absorbance analysis has confirmed that NiS films possess a direct optical band gap whose values vary from 1.50 to 1.45 eV with annealing.