Structural, Optical and Sensing Properties of Cr-Doped TiO2 Thin Films
Undoped and chromium (Cr)-doped TiO2 thin films were deposited at room temperature by the RF magnetron sputtering method onto oxidized silicon. The composition, microstructure and surface morphology of the sputter-deposited films were studied by means of X-ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM) respectively. The deposited films were found to be mainly amorphous. The Cr incorporation induces a more compact films compared to undoped ones. Using variable angle spectroscopic ellipsometry the optical constants (n and k) and energy band gap of the Cr-doped films were found to depend on their Cr content. Thus, the band gap of the TiO2:Cr films can be varied from 3.3 eV to 1.89 eV by increasing their Cr content. The TiO2:Cr films were integrated into gas sensing devices and their sensing properties (sensor response, response and recovery time) towards ethanol were systematically investigated as a function of their Cr content. This has led to identify an optimum Cr-doping condition, which corresponds not only to the highest sensor response but also to the shortest response and recovery time of the sensors. The deposited TiO2 films shows an n-type conducting behaviour for Cr doping concentration lower than 13% however a p-type conduction is observed at higher doping content.
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Document Type: Research Article
Publication date: 2011-10-01
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