Characteristics of indium-tin oxide thin films grown on flexible plastic substrates at room temperature

Transparent and conductive indium-tin oxide (ITO) thin films were deposited on polyethersulfone (PES) flexible plastic substrates by DC magnetron sputtering. The crystalline structure and optical-electric characteristics were investigated to achieve the optimum room-temperature growth conditions. The crystalline orientation and the surface morphology were characterized by X-ray diffraction (XRD) and the atomic force microscopy (AFM), respectively. The ITO/substrate interfaces were observed by scanning electron microscopy (SEM). In addition, the resistivity, the Hall effect, and the optical transmittance were measured to characterize the photo-electric properties of as grown films. It is found that the ITO films are epitaxially grown with the orientations < 222 >, < 400 >, and < 440 > perpendicular to the film plane. Moreover, the resistivity of thin film decreases with an increase in the (2 2 2) diffraction intensity. The obtained optimum growth conditions for the room-temperature deposition are: DC power = 300 W, deposition pressure = 2.0 mTorr, and the gas of Ar:O-2 = 100:1. With the optimum conditions, the resistivity of 6.42 x 10(-3) Omega CM, carrier concentration of 1.13 x 10(19) cm(-3), and transmittance of 851%,, for films grown on PES substrates are obtained. Comparing the results with those reported by other workers, we conclude that improved photo-electric properties of ITO films can be obtained by using the DC magnetron Sputtering technique at room temperature. (c) 2007 Elsevier Ltd. All rights reserved.