Structural study of undoped and (Mn, In)-doped SnO2 thin films grown by RF sputtering

Undoped and 5%(Mn, In)-doped SnO2 thin films were deposited on Si(1 0 0) and Al2O3 (R-cut) by RF magnetron sputtering at different deposition power, sputtering gas mixture and substrate temperature. X-ray reflectivity, was used to determine the films thickness (10-130 nm) and roughness (similar to 1 nm). The combination of X-ray diffraction and Mossbauer techniques evidenced the presence of Sn4+ in an amorphous environment, for as-grown films obtained at low power and temperature, and the formation of crystalline SnO2 for annealed films. As the deposition power, substrate temperature or O-2 proportion are increased, SnO2 nanocrystals are formed. Epitaxial SnO2 films are obtained on Al2O3 at 550 degrees C. The amorphous films are quite uniform but a more columnar growth is detected for increasing deposition power. No secondary phases or segregation of dopants were detected. (c) 2008 Elsevier B.V. All rights reserved.