Optical Properties of Undoped and Indium-doped Tin Oxide Thin Films

Abstract

Thin films of Tin Oxide (SnO 2 ), having thickness of 200 nm, were formed on to glass substrates by thermal evaporation of high-purity SnO 2 powder in vacuum at various substrate temperatures (T S ), ranging between 25 and 200C. SnO 2 films with varying thickness were also prepared for a fixed T S = 100C. Further, doping of SnO 2 films with Indium (In) was accomplished through solid state diffusion process by successive deposition of SnO 2 and In films and subsequent annealing at 200C for 10 minutes. Both undoped and doped films were characterized optically by UV-VIS-NIR spectrophotometry in the photon wavelength ranging from 300 to 2500 nm. In the visible photon wavelength range, the average optical transmittance (T%) of the films with varying T S was found to be 85%. The maximum value of T % was found to be 89 % around the wavelength of 700nm. The variation of absorption coefficient with photon energy in the fundamental absorption region is the steepest for T S = 100C. The sub-band gap (SBG) absorption is also minimum for this T s . A fluctuating behavior of the band gap energy (E g ) with T s is observed attaining the highest value of 3.59 eV for T s = 100C. The band gap energy increases with thickness but T% in the visible range decreases. The T% in the visible range varies inversely with indium doping, being highest for undoped films. The E g increases upto 2 wt% In doping and gradually decreases for enhanced doping. It seems reasonable to conclude that In doping does not bring favorable optical characteristics. Undoped SnO 2 films having thickness of 200 nm and formed at substrate temperature of 100C yield essential acceptable properties for photovoltaic applications.

Effect of thickness on the optical properties of Gaas thin films

“…The maximum value of T% was found to be 80 for the film of thickness 500 nm. Indium-doped tin Oxide films showed T% as 89 (Chowdhury et al 2011). The behavior of the absorbance spectra is opposite completely to that of the transmittance spectra as shown in Fig.…”

Effect of Surface Passivation on Electrical Properties of Pd-F:SnO2 Thin Films Prepared by Spray Pyrolysis Technique

“…In this study SnO2 based thin films were prepared for gas sensing applications. SnO2 based thin films are polycrystalline with tetragonal rutile structure, non-stoichiometric, degenerate n-type semiconductor [2][3][4]. The films are transparent within the visible range of the spectrum and are chemically inert, mechanically hard and can withstand high temperatures [3,5,6].…”

Influence of Surface Passivation on Optical Properties of Spray Pyrolysis Deposited Pd-F:SnO2

“…SnO 2 based thin films have n-type conductivity that can be manipulated from normal to degenerate by suitably doping SnO 2 thin films with appropriate amount of noble metal (Pt, Pd), semi-metal (Sb, In, Bi) and halogens (F, Cl) [4]. SnO 2 based thin films are polycrystalline with tetragonal rutile structure and non-stoichiometric semiconductors [5,6,7]. Tin oxide can exist in two structures belonging to direct and indirect optical transitions, with different band gaps; a direct band gap that ranges from 3.6 to 4.6eV [8] at room temperature and indirect band gap of about 2.6eV [9].…”