Electrical and Optical properties of ITO Films Prepared by Ion-Assisted Deposition at Ambient Substrate Temperatures

Abstract

Traditionally, to achieve low resistivity and high transmission indium-tin oxide (ITO) films were deposited at elevated substrate temperatures about 400o C. In some cases, films deposited at low substrate temperatures can then annealed at higher temperature to achieve lower resistivity. In this paper thin films of ITO with various oxygen flow rates were prepared by ion-assisted electron beam evaporation at ambient substrate temperature. The electrical and optical properties of ITO thin films have been investigated as a function of oxygen flow rate, rate of deposition and the layer thickness. The transmittance and optical band-gap energy were measured by spectrophotometer, whereas the sheet resistance was measured using four-point probe method. It has been found that at 25 sccm oxygen flow, 0.4 nm/sec rate of deposition and 140 nm layer thickness were suitable for improving the properties of ITO films. The optical transmittance, optical band-gap and the resistivity were 92%, 4.2 eV and 175x10-4Ω-cm, respectively.