Optimization of electrical conductivity of SnS thin film of 0.2 < t ≤ 0.4 μm thickness for field effect transistor application

This study is focused on the investigation of SnS thin film for transistor application. Electron traps, associated to the grain boundary effect, alter the electrical conductivity of the SnS semiconductor thin film, thereby militating on the attainment of the threshold voltage required for operation as a transistor. SnS semiconductor thin films of 0.20, 0.25, 0.30, 0.35, 0.40 μm thickness were deposited using aerosol assisted chemical vapour deposition on glass substrates. Surface profilometry, scanning electron microscopy, energy dispersive X-ray spectroscopy and hall measurements were used to characterize the thickness, microstructure, elemental composition and electrical properties of the SnS thin films. SnS thin films were found to consist of Sn and S elements whose composition varied with increase in thickness. The film conductivity was found to vary with grain size and grain boundary, which is a function of the film thickness by itself. The SnS film of 0.4 μm thickness shows optimal grain growth with a grain size of 130.31 nm signifying an optimum for the as-deposited SnS films as the larger grains reduce the number of grain boundaries and charge trap density allowing charge carriers to move freely in the lattice, thereby causing a reduction in resistivity and increase in conductivity of the films which is essential for obtaining the threshold voltage for a transistor semiconductor channel layer. The carrier concentration of 1.438 x 10¹³ c^-3, conductivity of 2.768 x 10^-6 (Ωcm)^-1 due to low resistivity of 3.612 x 10⁵ Ωcm of 0.4 μm SnS thin film thickness is optimum and favours the attainment of the threshold voltage for a field effect transistor operation: hence, making possible the application of SnS thin films as semiconductor channel layers in a field effect transistor. (author)