Influence of oxygen growth pressure on laser ablated Cr-doped In2O3 thin films

We present a systematic investigation of the effects of oxygen growth pressure on the structural, optical, and electrical properties of In2O3:Cr thin. lms grown by pulsed laser deposition. X-ray diffraction analysis showed increases in lattice constant from 10.103 angstrom to 10.337 angstrom, and in particle size from 13.9 nm to 35.5 nm as the oxygen growth pressure increased from 7.5 x 10 (6) Torr to 7.5 x 10 (3) Torr, respectively. The observed shift in the X-ray diffraction peaks to lower angles was assumed to be caused by the reduction in the lattice defect density, precisely oxygen vacancies. The optical transparency increased with partial oxygen pressure (Po-2), and an average transmittance of similar to 85% was obtained at 7.5 x 10 (3) Torr. The. lms are highly conducting with resistivity as low as 2 x 10 (4) Omega cm and mobility as high as 133 cm/V s. Temperature dependent resistivity measurements in the 45 < T < 300 K temperature range reveal that. lms grown at 7.5 x 10(-6) <= Po-2 <= 7.5 x 10(-4) Torr exhibit negative temperature coefficient of resistivity (TCR) below approximately T = 60 K, T = 120 K, T = 160 K; then positive TCR in the temperature intervals 60 < T < 300 K, 120 < T < 300 K, and 160 < T < 300 K, respectively. This suggests that two disparate mechanisms govern electrical dc transport in the two temperature regions. Film grown at Po-2 of 7.5 x 10 (3) Torr displayed typical semiconducting behavior with negative TCR in the whole temperature region. (C) 2009 Elsevier B. V. All rights reserved.