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Rutile and anatase phase TiO2 films obtained on unheated substrates by matched pulse mode and pulse parameters in reactive magnetron sputtering

: Frach, P.; Zywitzki, O.; Goedicke, K.; Gottfried, C.; Klinkenberg, S.; Sahm, H.; Modes, T.

Klages, C.-P.; Gläser, H.J. ; Fraunhofer-Institut für Schicht- und Oberflächentechnik -IST-, Braunschweig; Fraunhofer-Institut für Elektronenstrahl- und Plasmatechnik -FEP-, Dresden:
4th International Conference on Coatings on Glass 2002. Proceedings : Advanced Coatings on Glass & Plastics for Large-Area High-Volume Products, November 3 - November 7, 2002, Braunschweig, Germany
Braunschweig, 2002
International Conference on Coatings on Glass (ICCG) <4, 2002, Braunschweig>
Conference Paper
Fraunhofer FEP ()

Crystalline TiO2 films are in the focus of interest because of their specific properties compared to amorphous films. The rutile phase exhibits high refractive index, high hardness and high value of Young's modulus. Therefore and because of the high dielectric constant and thermal stability it became interesting for optical coatings [1-6], microelectronic applications [7] and protective layers [8]. The hydrophilic and photocatalytic behavior [9-11] of anatase phase TiO2 films allows to create products with new properties like easy to clean surfaces, "self-cleaning" windows, anti-fogging glass, self-sterilizing and antibacterial tiles or photocatalytic air cleaning and water purification devices.
According to the state of the art the use of elevated temperature during deposition or annealing after deposition above 300°C is necessary to obtain crystalline TiO2 layers by vacuum deposition methods [12, 13]. Therefore these processes are limited to temperature resistant substrates like glass. On the other hand there is a call for optical, photocatalytic and hydrophilic layers on temperature sensitive materials. Zeman [14] made investigations using rf reactive sputtering technique on unheated substrates to achieve crystalline TiO2 films. Unfortunately the deposition rate is very low with this method (< 3.2 nm/min).
A lot of applications require a high rate deposition technique, because of the large surfaces to be coated. The aim of our work was to use the reactive medium frequency pulse magnetron sputtering (PMS) technique for the high rate deposition of crystalline TiO2 films on unheated substrates. Recent observations lead us to the conclusion that pulse mode and duty cycle significantly influence the particle bombardment onto the growing film on the substrate [15]. Therefore the influence of these new parameters on the film structure and different film properties of TiO2 films should be investigated.