Synthesis, structural, linear and nonlinear optical properties of chromium doped SnO2 thin films

Abstract The present work concentrates on some physical investigation of the undoped and Cr doped SnO 2 thin films deposited onto precleaned glass substrates by the spray pyrolysis system. The physical properties of the undoped and Cr doped SnO 2 thin films were investigated by the X-ray diffraction (XRD), atomic force electron microscope (AFM), field emission scanning electron microscope (FESEM), four-probe method and double beam spectrophotometer. The undoped and Cr doped SnO 2 films display a polycrystalline nature with orthorhombic crystal structure. The linear optical constants energy gap E g , refractive index n , absorption coefficient α , static refractive index n o , oscillation energy E o , dispersion energy E d and the Urbach energy of the undoped and Cr doped SnO 2 thin films were evaluated. The investigated films exhibit a direct energy gap and their values decrease with the increasing of Cr doping content while the Urbach energy follows a reverse behavior. On the other hand, the nonlinear optical constants (third-order nonlinear susceptibility χ ( 3 ) and nonlinear refractive index n 2 ) have been increased with increasing the Cr doping content. Finally, it has been found that the sheet resistance and conductivity of the synthesized thin films were enhanced by increasing the Cr doping content. The 5 wt% Cr doped SnO 2 thin film has a high value of the figure of merit among other films.