Electrical properties of vacuum-annealed titanium-doped indium oxide films

Titanium-doped indium oxide (ITiO) films were deposited on Corning glass 2000 substrates at room temperature by radio frequency magnetron sputtering followed by vacuum post-annealing. With increasing deposition power, the as-deposited films showed an increasingly crystalline nature. As-deposited amorphous ITiO films obtained at 20 W began to crystallize at the annealing temperature of 155 degrees C. Although there was no significant change in the crystalline structure of the films, electron mobility improved gradually with further increase in the annealing temperature. After post-annealing at 580 degrees C, the highest electron mobility of 50 cm(2) V(-1) s(-1) was obtained. Compared with the amorphous ITiO films, the ITiO films with a certain degree of crystallinity obtained at high deposition power were less affected by the vacuum annealing. Their electron mobility also improved due to post-annealing, but the increase was insignificant. After post-annealing, the optical transmission of the 325 nm-thick ITiO films showed approximately 80% at wavelengths ranging from 530 to 1100 nm, while the sheet resistance decreased to 10 Omega/sq. This makes them suitable for use as transparent conductive oxide layers of low bandgap solar cells. (c) 2011 Elsevier B. V. All rights reserved.