Influence of Substrate Temperature on Electrical and Optical Properties of Sputtered Binary SnO 2 -Al 2 O 3 Thin Films on Slide Glasses

Abstract SnO 2 -Al 2 O 3 (SAO) binary thin films were prepared on slide glasses substrates by RF magnetron sputtering. The influence of the substrate temperature on the surface morphology, crystal structures, electrical and optical properties were analyzed by the scanning electron microscopy (SEM) images, X-ray diffraction (XRD) patterns, four-probe measuring, UV-IR and photoluminescence (PL) spectra. With increasing substrate temperature, the grain sizes of SAO binary films are increased. Uniform patterns and large size grains indicate a better surface morphology and crystallinity of SAO films, which are verified by SEM and XRD investigations. All the films have a high average transmittivity of ∼80%∼90% in visible light region 400∼800 nm. The calculated band gap is in a range of ∼4.11∼4.14 eV, and the measured sheet resistances of SAO films are in a range of ∼7.0×10 4 to ∼9.4×10 4 Ω/□. At proper sputtering temperature, the band gap can be widened, and the sheet resistances can be reduced. The PL emissions from the films in UV and red bands were also observed. These polycrystalline SAO films can be used in the application of transparent conductive oxide (TCO) films, solar cell windows, sensors, as well as lighter emitters.