Influence of RF power on the growth mechanism, preferential orientation and optoelectronic properties of nanocrystalline ITO films

Nanocrystalline ITO thin films were deposited by the RF sputtering technique using various RF power values keeping the substrates at room temperature. An indepth study of the influence of RF power on the preferential orientation, optical, electrical and surface morphological properties was conducted by varying the RF power from 50 W to a maximum of 350 W. X-ray diffraction results confirmed the formation of nanocrystalline ITO films at all RF power values. At 250 W, the ITO films showed preferential orientation along (400) plane. Below and above this power, the films showed (222) orientation. It was observed from the optical transmittance studies that the bandgap value increased from 3.55 to 3.70 eV when the RF power was varied from 50 to 250 W. The resistivity value showed a minimum of 4.2 x 10(-3) Omega cm and the grain size reached a maximum of 125 nm for the ITO film deposited at 250 W. The XPS, EDAX and AFM results revealed the formation of stoichiometric and smooth ITO films, which contained nano-sized grains distributed uniformly all over the surface. These results show that the nanocrystalline ITO films deposited with 250 W RF power under the optimized conditions at room temperature, have the required optoelectronic and surface morphological properties useful for the fabrication of devices at a relatively lower temperature. (C) 2010 Elsevier B.V. All rights reserved.