Influence of the film thickness on the structure, optical and electrical properties of ITO coatings deposited by sputtering at room temperature on glass and plastic substrates

Transparent and conductive indium tin oxide (ITO) films with thickness between 0.2 and 0.7 mu m were deposited by sputtering at room temperature on glass and polyethylene terephthalate (PET) substrates. All films were polycrystalline, with crystallite size increasing and lattice distortion decreasing when the film thickness was increased. Besides, transmission in the near-infrared region is found to be decreasing and carrier concentration increasing when the film thickness was increased. For the same thickness, the lattice distortion is slightly lower and the carrier concentration higher for the layers grown on PET substrates. A direct relationship between the lattice distortion and the free carrier concentration has been established, applying to the films grown on glass and plastic substrates. By adjusting ITO coating thickness, sheet resistance below 15 Omega sq(-1) and average visible transmittance about 90% have been achieved by sputtering at room temperature.