Indium molybdenum oxide thin films: A comparative study by two different RF sputtering systems

Indium molybdenum oxide thin films were deposited using different radio-frequency sputtering units on glass substrates at room temperature from an In2O3 (95 wt.%): Mo (5 wt.%) target. The film thickness ranges between 160 and 275 nm. The chamber volume of Unit-1 was ∝2.4 times larger than that of Unit-2. Apart from the chamber volume, a significant difference between the two units was the sputtering pressure. The films were characterized by their structural, morphological, optical, and electrical properties. A strong reflection from (222) plane was obtained for the ∝275 nm thick films deposited in Unit-1. The films deposited with <275 nm thickness and those deposited in Unit-2 are close to amorphous with a small crystalline fraction. The surface of the films deposited in Unit-1 is comprised of randomly arranged crystallites, which is restructured with the increasing film thickness to become a well defined ''rice field'' like structure (275 nm thick). The films deposited in Unit-2 are comprised of many holes on the surface that is presumably due to back sputtering. The average visible transmittance calculated in the wavelength between 400 and 800 nm ranges from 70 to 82%. The optical band gap is found to vary between 3.80 and 3.86 eV. The lowest bulk resistivity of the films deposited in Unit-1 was increased from ∝4.06 x 10-3 to 4.07 x 10-1 Ωcm when deposited in Unit-2. The carrier concentration was decreased from 1.31 x 1020 to 1.03 x 1018 cm-3 but the Hall mobility increased from 11.7 to 15.0 cm2V-1s-1. (Abstract Copyright [2009], Wiley Periodicals, Inc.)