Fabrication of Anatase TiO 2 Thin Film Using Pulsed DC Magnetron Sputtering
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Fabrication of Anatase TiO2 Thin Film Using Pulsed DC Magnetron Sputtering Ibrahim A. Al-Homoudi1, Linfeng Zhang2, Erik F. McCullen2, Changhe Huang2, L. Rimai2, R.J. Baird2, K.Y.Simon Ng3, R. Naik4, G.W. Auner2, G. Newaz1 (1) Mechanical Engineering Dept.; (2) Electrical and Computer Engineering Dept; (3) Chemical Engineering and Material Science Dept.; (4) Physics and Astronomy Dept.
Wayne State University, Detroit, Michigan, 48202. Abstract TiO2 thin films (500 – 1000 nm in thickness) were deposited using pulsed DC magnetron reactive sputtering, on glass substrates. The depositions used a Ti source in an Ar+O2 gas mixture with different parameters of power (350 - 500W), substrate temperature (no additional heat - 400°C), growth pressure (3.0 - 5.0 mTorr) and oxygen gas flow rate (6.0 - 8.0 sccm). The x-ray diffractions (XRD) show amorphous and/or anatase phases depending on the deposition conditions. The films were found to be amorphous at lower substrate temperature and at lower powers. The sample with 4 mTorr, 400W of power, a substrate temperature of 250 C with 7.0 sccm of oxygen flow has the best crystalline quality. The temperature dependent electrical conductivity measurement in air for the above films shows an exponential increase in conductivity with temperature. Introduction Recently, titanium dioxide (TiO2) materials have attracted more attention because of the extensive use in a great variety of applications. TiO2 thin films are attractive for optical and electronic applications because they have a high refractive index, a high dielectric constant and good physical and chemical stability [1]. Thin films of TiO2 used as capacitor dielectrics, heat reflecting layers and waveguides have been shown to be resistant to corrosive and mechanical attack and to be stable over long time periods [2]. Jun and Duren [3] used a TiO2–Nb2O5 composite as an oxygen sensing device with excellent step response. SnO2–TiO2 mixed oxide thin films were prepared as gas sensor for hydrogen detection in air and argon [4]. Ferroni et. al. [5] used TiO2 thin films to detect 20 ppm of NO2 in the temperature range of 350-800°C, suitable for monitoring composition of engine exhaust. TiO2 is a markedly inert, stable compound found in nature in three crystalline forms rutile, anatase (both tetragonal) and brookite (orthorhombic). Anatase is a semiconductor with a band gap Eg= 3.2 eV and has also been shown to have significant and rapid electrical response to ethanol in the temperature range between 300 and 400ºC [6]. Carotta et al. [7] fabricated thick films of nanostructured TiO2 anatase for environmental monitoring application. The response was highest for the films with the lowest grain size. A number of different techniques have been employed to synthesize TiO2 thin films, such as DC and RF reactive magnetron sputtering [5,8], Chemical Vapor Deposition (CVD) [9], ion beam assisted deposition (IBSD) [10], electron-beam (E-B) evaporation [11] and ion-assisted deposition (IAD) [12]. This study deals with structural and morphol
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