Sahar Moradi - Department of Physics, Faculty of Science, Urmia University, Urmia, Iran.
Hassan Sedghi - Department of Physics, Faculty of Science, Urmia University, Urmia, Iran.
Jamshid Asadi - Department of Physics, Faculty of Science, Urmia University, Urmia, Iran.

Optical properties of sol-gel spin coated Co-doped SnO2 thin film deposited on the glass substrate was investigated by using spectroscopic ellipsometry (SE) technique. SE measurements are done at three various incidence angles of light including 67.5°, 70° and 72.5°. Influeces of the incidence angle of light emitted by SE device on optical constants including the reflectance, refractive index, extinction and absorption coefficents were studied. By absorption coefficient values obtained from SE measurements and using Tauc equation, we determined the band gap energy values. Results showed the increase of incidence angle of light from 67.5° to 72.5° leads to decrease of the bandgap energy from 3.5 to 3.4 ev.

sol-gel, spin coating, spectroscopic ellipsometry, co-doped SnO2, incidence angle, band gap energy