Optical properties of nitrogen-doped SnO2 films:: Effect of the electronegativity on refractive index and band gap

The optical properties of nitrogen-doped SnO2 films with different N-2/(N-2+O-2) gas ratios grown by reactive sputtering were studied by spectroscopy ellipsometry. The optical dielectric functions of the films were simulated by the Tauc-Lorentz model. It was found that the refractive index and extinction coefficient of nitrogen-doped SnO2 films increase and the band gap has a redshift with the increase of the N-2 ratios. The general influences of the electronegativity and bond ionicity on the band gap, the refractive index in the spectral region below the fundamental absorption edge of nitrogen-doped SnO2, and other doped semiconductors are demonstrated. (C) 2008 American Institute of Physics.