Preparation of TiO2 thin films by laser ablation for photocatalytic applications

Abstract

Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputteringBandgap renormalization in titania modified nanostructured tungsten oxide thin films prepared by pulsed laser deposition technique for solar cell applications J. Appl. Phys.Thin titanium dioxide ͑TiO 2 ͒ films were deposited by pulsed KrF excimer laser ablation deposition system using a titanium oxide target. The effects of substrate temperature and oxygen partial pressure on the phase formations of various microstructures were investigated by x-ray diffraction ͑XRD͒, scanning electron microscopy ͑SEM͒, Raman scattering spectroscopy, and UV-Vis spectrophotometer. The film structures range from amorphous to mixed phase of anatase and rutile to pure anatase. Increasing the substrate temperature improves the quality of anatase phase of crystalline TiO 2 films. The oxygen pressure in the range between 15 and 60 mTorr shows a single anatase phase in TiO 2 films while the rutile and anatase mixed phases were observed elsewhere. The band gap of TiO 2 films varied from 2.72 to 3.27 eV with increasing oxygen partial pressure while the film structures changed from rutile phase to anatase phase. The surface area of TiO 2 films increased as oxygen partial pressure in film deposition. The photocatalytic performance evaluated by degradation of methylene blue in UV light was distinguishable in the TiO 2 films with high anatase phase and surface area.

Formation of Photocatalytically Active TiO₂ Layers on Ti–Nb Alloys by Two-Step Thermal Oxidation

“…The reported k values and those found herein are in agreement; however, the effect of anatase fraction on the k value was not shown in Ref. 23. Jung and Park 24) studied the decomposition of trichloroethylene using the photocatalytic activity of TiO 2 synthesized by the sol-gel method and reported that TiO 2 with an anatase fraction of 0.9 exhibited a superior decomposition rate than that with a single-phase anatase.…”

“…In Fig. 8, the rate constants of MB decomposition on the anatase-type TiO 2 layer ( f A = 1), fabricated by the pulsed laser ablation method, 23) are shown for comparison, where the irradiation conditions, such as the UV light source irradiance of 1.6 mW·cm ¹2 and the initial MB concentration of 0.031 mM, Formation of Photocatalytically Active TiO 2 Layers on TiNb Alloys by Two-Step Thermal Oxidation were close to those used in this study. The reported k values and those found herein are in agreement; however, the effect of anatase fraction on the k value was not shown in Ref.…”

Non-equilibrium Growth Processes of Porous TiO2 Nanocrystal-films during Pulsed Laser Ablation

“…Control of both crystal and aggregated structures are desired for catalytic applications. However the effects of background gas on the crystal structure and/or morphology of TiO 2 are described in many literatures, the correlation between structure and preparation conditions is discussed rather empirically [7][8][9][10][11][12]. The formation processes of atomic microstructure and aggregated nanocrystals have been clarified for PLA of silicon target in H 2 gas [6].…”

Effect of Target Sintering Temperature on the Morphological and Optical Properties of Pulsed Laser Deposited TiO2 Thin Films

“…The transformation to rutile phase is irreversible, and the melting point of TiO 2 is 1858 • C [8,14,15]. Furthermore, the currently known methods to crystallize amorphous TiO 2 films into anatase or rutile phases require the annealing step, including oxygen plasma treatment [16][17][18]. Anatase crystals exhibit excellent optical properties, higher photocatalytic activity and gas sensing properties than rutile ones, and a lower electron-hole recombination rate.…”