The optical properties of nanostructured SnO2 films deposited by sol gel dip coating method

In this work, undoped and In doped SnO2 films were fabricated by sol-gel method through dip coating on borofloat glass substrates. The undoped SnO2 films were deposited in air between 400 and 600oC to get optimum deposition temperature in terms of crystal quality and hence In-doped SnO2 films were deposited in air at 600oC. The effect of both deposition temperature and In content on structural, morphological, optical and electrical properties was investigated. X-ray diffraction patterns of the films show that the films are polycrystalline and hexagonal in structure. Structural parameters such as grain size, lattice parameters and texture coefficients were calculated. Surface morphology was investigated by a field emission scanning electron microscope (FESEM). The compositional analysis of the films was confirmed by energy dispersive X-ray spectrometer (EDS). The optical band gaps of the SnO2 films were determined by using the analysis of optical absorption spectra. Films have the direct transition and the optical band gaps of the films are found to be between 3.61 and 3.88 eV. The optical band gap tended to decrease with increasing In content. The Van der Pauw method was used to measure the sheet resistance of the films.