Some studies on highly transparent wide band gap indium molybdenum oxide thin films rf sputtered at room temperature

Transparent wide band gap indium molybdenum oxide (IMO) thin films were rf sputtered on glass substrates at room temperature. The films were studied as a function of sputtering power (ranging 40–180 W) and sputtering time (ranging 2.5–20 min). The film thickness was varied in the range 50–400 nm. The as-deposited films were characterized by their structural (XRD), morphological (AFM), electrical (Hall Effect measurements) and optical (visible-NIR spectroscopy) properties. XRD studies revealed that the films are amorphous for the sputtering power ≤ 100 W and the deposition time ≤ 5 min, and the rest are polycrystalline with a strong reflection from (222) plane showing a preferential orientation. A minimum bulk resistivity of 2.65 × 10 − 3 Ω cm and a maximum carrier concentration of 4.16 × 10 20 cm − 3 are obtained for the crystalline films sputtered at 180 W (10 min). Whereas a maximum mobility (19.5 cm 2 V − 1 s − 1 ) and average visible transmittance (∼ 85%) are obtained for the amorphous films sputtered at 80 W and 100 W respectively for 10 min. A minimum transmittance (∼ 18%) was obtained for the crystalline films sputtered at 180 W (∼ 305 nm thick). The optical band gap was found varying between 3.75 and 3.90 eV for various sputtering parameters. The obtained results are analyzed and corroborated with the structure of the films.