Substrate-induced changes of structural and optical properties of SnS films prepared by glancing angle deposition

Tin (II) sulfide (SnS) films were prepared using physical vapor deposition coupled with glancing angle deposition technique at zero and high oblique incident vapor angles (α = 65° and 85°). The resulting films were all nanostructured with thin nano-sheets. The thickness of the nano-sheets increased upon deposition angle increment due to shadowing and re-emission effects. In order to investigate substrate-induced changes, the films were deposited on glass, indium tin oxide, and fluorinated tin oxide substrates. The X-ray diffraction analysis indicated that the thin films coated at different incident angles and substrates were crystallized in single phase with orthorhombic structure while a change of the growth orientation observed in the samples prepared at α = 65° and 85°. In addition, the presence of Sn2S3 phase in some samples was also detected. The top and cross-sectional images of the samples, obtained by field emission scanning electron microscopy, confirmed considerable changes in the structure and morphology of individual nano-plates as which was a function of the incident deposition angle and substrate type. Atomic force microscopy analysis confirmed that the substrate type and deposition angle have an effect on the apparent average surface roughness and porosity. The optical band-gaps of the samples prepared at α ≥ 65° were higher than those prepared at α = 0°. In near-IR spectral range, significant changes in the refractive index of all the samples deposited at α = 85° were observed.