Optical investigations on PVA capped SnS nanocrystalline films deposited by CBD process

Abstract

Tin monosulphide (SnS) nanocrystalline films, capped by polyvinyl alcohol (PVA) were successfully deposited on glass substrates using chemical bath deposition (CBD). The films were deposited at different deposition times that vary in the range, 45–90 min The XRD spectra indicated that PVA capped SnS layers were polycrystalline in nature and exhibiting orthorhombic structure. The average crystallite size was evaluated using W-H plots. Cross section view of SEM micrographs were used to determine the thickness of the films. The optical behaviour of all the deposited layers was investigated in relation to deposition time. The studies revealed a very high optical absorption coefficient of ∼105 cm−1 for all the deposited layers and the optical band gap varied from 1.79 eV to 1.55 eV with increase of deposition time. The band gap values obtained were higher than the bulk value of 1.3 eV, which is attributed to quantum confinement effect. The size of particles, calculated using Brus equation, varied marginally in the range, 5.8–8.4 nm with increase of growth time. The optical parameters such as refractive index, extinction coefficient, high frequency dielectric constant, optical carrier concentration, relaxation time and optical conductivity were also determined.