Opto-electrical characterizations of DC-sputtered ITO thin films

The effect of various thicknesses (6nm-74nm) on the optical, electrical, and surface topology properties of Tin-doped Indium Oxide (ITO) thin conductive films (TCF) on Si and glass substrates has been studied. The ITO thin films were prepared by direct-current (DC) sputtering at room temperature using 1-meter diameter high vacuum coating chamber at GSFC. The Ar partial pressure was 2 × 10^-3 Torr and DC power was kept at 200W. The film resistivity was measured by a four-point probe method at room temperature. Transmittance of ITO films on glass were characterized in the 200-2500nm range through optical spectrophotometry. Optical properties (n, k) were derived through ellipsometry. The surface topology and morphology were examined by scanning white light interferometry (SWILI) and atomic force microscopy (AFM). As an exemplary result, the transmittance of glass substrate coated with a 22.9 nm thick ITO thin film, normalized to the transmittance of the bare glass substrate, is 0.985 at λ=550nm and 0.988 at λ=1064nm. This sample presents a resistivity of 7.29 × 10^-4 Ω-cm, and a surface roughness of 0.4 nm.