Characterization of nanocrystalline Ti films deposited by DC magnetron sputtering onto FTO glass substrate
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Mehdi Abdi Physik Department, Technische Universität München, 85748 Garching, Germany (Received 3 March 2015; accepted 28 July 2015)
Titanium (Ti) thin films were deposited by DC magnetron sputtering at conventional conditions with different substrate temperature, deposition rate, and inert gas pressure. The compositional, structural, morphological, and optical properties of the Ti films were investigated. It is shown that the films were crystalline with a-Ti phase and hcp structure only. The crystallinity increased with increase in substrate and deposition rate. Analysis of the atomic force microscopy images shows that the films were uniform, crack free, and adhered well to the substrate. It is found that, a strong relation existed between the structural and optical properties of the films. The optical properties of the Ti films were most influenced under the deposition conditions. From this dependence, the optimum deposition conditions are obtained to prepare metallic, crystalline, and dense Ti films with smooth surface under conventional conditions.
I. INTRODUCTION
Recently, titanium (Ti) film has drawn extraordinary attention for its applications in microelectronics, microelectromechanical systems, and medical industry owing to its remarkable photoelectric performance, excellent corrosion resistance, and good mechanical properties.1–3 As the starting substrate materials for preparing TiO2 nanotube arrays by anodization, the quality (dense, uniform) of Ti films and their adherence to the substrate are critical to the formation process of titania nanotubes. Nowadays, TiO2 nanotube arrays on conductive glass substrates (fluorine-doped tin oxide, F:SnO2, FTO) had been widely used in electrochromic devices and dyesensitized solar cells.4,5 Many techniques devoted to prepare Ti films on the desired substrate have been developed. Among all these techniques, sputtering method has been extensively used to deposit Ti thin films on conductive glass substrates.6,7 Sputtering involves physical ejection of fine particles of a material such as its atoms or molecules from a pure target and their condensation and nucleation onto a substrate. Ti films produced by sputtering processes commonly exhibit a wide variety of micro- and nanostructural properties including grain size, lattice defects, crystallographic orientation, and surface morphology. The unique properties and various applications of Ti generally depend on its morphology, structure, and chemical Contributing Editor: Andrea M. Hodge a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.249 J. Mater. Res., Vol. 30, No. 20, Oct 28, 2015
nature. Therefore, so far several research groups have tried to analyze the physical and chemical characteristics of bulk Ti and Ti films.8–10 Many investigators have noted that the formation of films with a specific structure and morphology depends upon deposition conditions, such as substrate temperature, deposition rate, angle of incident, inert gas pressure, surface roughness of the substrate, and sputterin
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