Effect of Annealing Temperature on the Properties of ITO/Au/ITO Films

Abstract

Transparent Sn-doped <TEX>$In_2O_3$</TEX> (ITO) single-layer and ITO/Au/ITO multilayer films were deposited on glass substrates by reactive magnetron sputtering to compare the properties of the films. They were then annealed in a vacuum of <TEX>$1{\times}10^{-2}\;Pa$</TEX> at temperatures ranging from 150 to <TEX>$450^{\circ}C$</TEX> for 20 min to determine the effect of the annealing temperature on the properties of the films. As-deposited 100 nm thick ITO films exhibit a sheet resistance of <TEX>$130{\Omega}/{\square}$</TEX> and optical transmittance of 77% at a wavelength length of 550 nm. By inserting a 5 nm-thick Au layer in ITO/metal/ITO (IMI) films, the sheet resistance was decreased to as low as <TEX>$20{\Omega}/{\square}$</TEX> and the optical transmittance was decreased to as little as 73% at 550 nm. Post-deposition annealing of ITO/Au/ITO films led to considerably lower electrical resistivity and higher optical transparency. In the Xray diffraction pattern, as-deposited ITO films did not show any diffraction peak, whereas as-deposited ITO/ Au/ITO films have Au (222) and <TEX>$In_2O_3$</TEX> (110) crystal planes. When the annealing temperature reached the 150 - <TEX>$450^{\circ}C$</TEX> range, the both diffraction peak intensities increased significantly. A sheet resistance of <TEX>$8{\Omega}/{\square}$</TEX> and an optical transmittance of 82% were obtained from the ITO/Au/ITO films annealed at <TEX>$450^{\circ}C$</TEX>.