Structural, Morphological and Optical Properties of Sn3Sb2S6 Thin Films Synthesized by Oblique Angle Deposition

The oblique angle deposition technique has attracted a lot attention in many different applications due to its unique advantage of programmable nano-columns. In this work we use this technique to investigate the physical properties of obliquely thermal evaporated Sn3Sb2S6 thin films deposited onto unheated glass and silicon substrates, inclined from the flux vapor source at the deposition angles 0 degrees, 40 degrees, 60 degrees, 75 degrees and 85 degrees. X-ray diffraction (XRD) and UV-Visible and near infrared (UV-Vis-IFR) analysis were used respectively to characterize the structural and optical properties of the layers. The influence of flux angle on the surface morphology and the microstructure was investigated by using scanning electron microscopy. The optical constants were obtained from analysis of the experimental recorded transmission and reflectance spectral data over the wavelength range 300 nm to 1800 nm. The band gaps of the synthesized thin films were found to be direct allowed transitions and increased from 1.44 eV to 1.66 eV with increasing gamma from 0 degrees to 85 degrees, respectively. The absorption coefficients of the films are in the range of 10(5) cm(-1) to 10(6) cm(-1). The refractive indexes were evaluated in the transparent region in terms of the envelope method suggested by the Swanepoel model. It has been found that the refractive index decreases from 2.66 to 2.06 with increasing deposition angle from 0 degrees to 85 degrees, respectively. The relationship between the flux incident angles gamma and the column angle beta was also explored. The oblique angle deposition films showed an inclined columnar structure, with columns tilting in the direction of the incident flux. The effective packing densities of the synthesized Sn3Sb2S6 thin films were calculated using Bruggeman effective medium approximation.