Phase development in sputter deposited titanium dioxide

Abstract

We report the formation of highly oriented rutile titanium dioxide films. Films of a primarily amorphous nature were grown on fused silica by rf reactive sputter deposition using a Ti target and rare gas (Ne or Ar)-O2 discharges. Post-deposition annealing was done at 350–1150 °C in air for 60 minute intervals, followed by an air cool. The phase mixture of the as-deposited films, determined by x-ray diffraction, was of two types: (I) amorphous + rutile + anatase, or (II) amorphous + rutile. All phases were highly oriented with (110) rutile planes and (101) anatase planes parallel to the substrate. Upon annealing, the amorphous component of films containing no anatase transformed entirely to rutile, even at temperatures where it is possible to form anatase, <800 °C, indicating that anatase requires ‘‘seeds’’ to form. The results of this study clearly demonstrate that the crystal structure of the as-deposited film determines the development of the rutile phase with post-deposition annealing.

An introduction to thin film processing using high-power impulse magnetron sputtering

“…11,[113][114][115][116] In general, TiO 2 films can grow in an amorphous and in two tetragonal crystalline structures; the rutile and the anatase phases, respectively. 117 The anatase phase exhibits interesting photocatalytic properties, 117 whereas the rutile phase exhibits one of the highest refractive indices in nature. 117 Deposition and/or annealing at high temperatures (700-900°C) have been reported to lead to the 110 formation of the rutile phase.…”

“…117 The anatase phase exhibits interesting photocatalytic properties, 117 whereas the rutile phase exhibits one of the highest refractive indices in nature. 117 Deposition and/or annealing at high temperatures (700-900°C) have been reported to lead to the 110 formation of the rutile phase. 117 The anatase phase is generally obtained at lower temperatures, 117 whereas deposition at room temperature often leads to the formation of amorphous films.…”

“…117 Deposition and/or annealing at high temperatures (700-900°C) have been reported to lead to the 110 formation of the rutile phase. 117 The anatase phase is generally obtained at lower temperatures, 117 whereas deposition at room temperature often leads to the formation of amorphous films. 117 In addition, the energetic bombardment by positively charged ions (facilitated by applying a negative bias voltage on the substrate) can promote the crystallization of TiO 2 films at room temperature.…”

“…117 The anatase phase is generally obtained at lower temperatures, 117 whereas deposition at room temperature often leads to the formation of amorphous films. 117 In addition, the energetic bombardment by positively charged ions (facilitated by applying a negative bias voltage on the substrate) can promote the crystallization of TiO 2 films at room temperature. 118 When HiPIMS is used, the rutile phase can be achieved even at room temperature, and the increase of the flux of energetic species toward the growing film favors the formation of the rutile at the expense of the anatase phase.…”

Effects of Annealing on the Morphology and Porosity of Porous TiO₂ Films Fabricated by Deposition of Aerosol Nanoparticles

“…9 Schematic illustration of the transformation of the film morphology larger than 14 nm (Zhang and Banfield, 1998;Hanaor and Sorrell, 2011). However, some investigations of the annealing effects on the transformation of TiO 2 films fabricated by sputter deposition (Wiggins et al, 1996), MOCVD (Won et al, 2001), and sol-gel dip-coating (Kim et al, 2002) reported that the transformation temperatures exceeded 600°C. Kumar et al (1993) investigated the difference in the transformation temperature between nanoparticle powder and nanoparticulate films both synthesized by the sol-gel method.…”