Structural and optoelectronic properties of indium doped SnO2 thin films deposited by sol gel technique

Abstract

Indium doped tin oxide (SnO2:In) thin films were deposited on glass substrates by sol–gel dip coating technique. X-ray diffraction pattern of SnO2:In thin films annealed at 500 °C showed tetragonal phase with preferred orientation in T (110) plane. The grain size of tin oxide (SnO2) in SnO2:In thin films are found to be 6 nm which makes them suitable for gas sensing applications. AFM studies showed an inhibition of grain growth with increase in indium concentration. The rms roughness value of SnO2:In thin films are found to 1 % of film thickness which makes them suitable for optoelectronic applications. The film surface revealed a kurtosis values below 3 indicating relatively flat surface which make them favorable for the production of high-quality transparent conducting electrodes for organic light-emitting diodes and flexible displays. X-ray photoelectron spectroscopy gives Sn 3d, In 3d and O 1s spectra on SnO2:In thin film which revealed the presence of oxygen vacancies in the SnO2:In thin film. These SnO2:In films acquire n-type conductivity for 0–3 mol% indium doping concentration and p type for 5 and 7 mol% indium doping concentration in SnO2 films. An average transmittance of >80 % (in ultra-violet–Vis region) was observed for all the SnO2:In films he In doped SnO2 thin films demonstrated the tailoring of band gap values. Photoluminescence spectra of the films exhibited an increase in the emission intensity with increase in indium doping concentration which may be due structural defects or luminescent centers, such as nanocrystals and defects in the SnO2.