Optical and electrical characterization of r.f. sputtered ITO films developed as art protection coatings

Transparent and conductive tin-doped indium oxide (ITO) films have been prepared by r.f. plasma sputtering technique in Ar and Ar + O₂ gas mixture. The influence of the deposition conditions, film thickness, and substrate heating, as well as the post-annealing treatment on the optical and electrical properties of the ITO films has been investigated.The present study has extended the optical behaviour characterization of the ITO films in a wide UV-VIS-IR spectral region in addition to the comprehensive optical studies of this material at shorter wavelengths.The optical constants: refractive index (n), extinction (k) and absorption (α) coefficient, and the optical band gap (E_go) have been calculated for the ITO films in the spectral range between 350 and 2500 nm. A combination of several well-known theoretical models has been applied to describe precisely the complex optical behaviour of ITO films in separate spectral parts. In this approach, a good overlapping between the experimental and the simulated spectra in the whole investigated spectral region has been achieved.The deposition conditions and the optical and electrical properties of the ITO films have been optimized with respect to the requirements for their applications in art protection coatings.