INFLUENCE OF POST-DEPOSITION ANNEALING ON THE INDIUM TIN OXIDE THIN FILMS GROWN BY PULSED LASER DEPOSITION

Abstract

Transparent thin-film Indium Tin Oxides (ITO) were prepared on glass substrates using a pulsed laser deposition (PLD) process with an average thickness of 150 nm. Post-deposition annealing was performed on the samples in a wide range of temperatures from 250 to 6500C. The surface structures of as-deposited and annealed ITO films were analyzed using the x-ray diffraction (XRD). Atomic Force Microscopy (AFM) was carried out on all samples to verify any change in the grain sizes, and in the roughness of the oxide thin film surfaces. The transmittance spectra of the annealed samples were also investigated using spectrophotometer measurements. Energy band gaps Eg were calculated from the optical spectra for all films. It was found that the optical band gap values decreased as the annealing temperature was increased. To compare the effect of the annealing on refractive index n and extinction coefficient k properties, additional measurements were done on the samples pre and post annealing using an ellipsometer. It is noted that the annealed ITO films resulted in a noticeable improvement in the crystalline structure and an increase in the surface roughness. Furthermore, their maintained good optical properties made them very favorable to be used in different disciplines such as anodes of the solar cells and as protective coatings in space windows.