The effect of argon pressure on the structural and photocatalytic characteristics of TiO2 thin films deposited by d.c. magnetron sputtering

Abstract

TiO 2 thin films of 200 -300 nm thickness were deposited by d.c. magnetron sputtering onto glass substrates from a semiconducting TiO 2Àx target in pure Ar using pressures between 0.1 and 1.0 Pa. The obtained TiO 2 coatings are transparent and have refractive indices between 2.5 and 1.9. Post deposition heat treatment at different temperatures was performed to achieve crystallization of anatase TiO 2 . The as-deposited and heat treated films were examined with UV -VIS (transmission), SEM and XRD to investigate the influence of the argon pressure during deposition on the structural development during heat treatment. Additionally, the photocatalytic activity of the films was tested by measuring the decomposition rate of ethanol in a controlled gas atmosphere simulating air, and was related to their respective microstructures. D

Atomic layer deposition of TiO2-nanomembrane-based photocatalysts with enhanced performance

“…4(a)). The increase of the XRD peak intensity indicates the presence of anatase TiO 2 with better crystallinity, [21][22][23][24] which are beneficial to the photocatalysis performance, as will be discussed later. Fig.…”

“…22,25-27 TiO 2 crystallinity will increase with increasing grain size due to the decreasing of the grain boundaries as defect states. 22 The defects can act as trap sites for the photogenerated charge carriers, increasing their probability of recombination. 22,28 Therefore, TiO 2 with fewer defect leads to increasing lifetime of charge carriers, and consequently more separated electrons and holes can migrate to the photocatalyst surface that are beneficial for reduction and oxidation processes in the decomposition of MO.…”

“…22 The defects can act as trap sites for the photogenerated charge carriers, increasing their probability of recombination. 22,28 Therefore, TiO 2 with fewer defect leads to increasing lifetime of charge carriers, and consequently more separated electrons and holes can migrate to the photocatalyst surface that are beneficial for reduction and oxidation processes in the decomposition of MO. 4,19,[29][30][31] In our previous study, 32 although it cannot be observed directly in XRD, the asprepared (without calcination) TiO 2 with fewer ALD cycles has a lower degree of local order, on the contrary more ALD cycles leading to an improvement of the degree of local order.…”

“…The degree of crystallization improves with increasing grain size as the influence of the grain boundaries decrease. 22 In addition, in the crystalline growth during calcination, the increase of nanomembrane thickness leading to an enhancement of the grain size due to a vertical growth. As a result, the degree of crystallization and the catalytic activity increases by raising the TiO 2 thickness (from 50 to 1000 ALD cycles, Figs.…”

Modeling evaporation, ion-beam assist, and magnetron sputtering of TiO2 thin films over realistic timescales

“…Argon ion bombardment during deposition also affects the density and stoichiometry of the resulting thin film. 8,10 Experimental evidence exists to confirm that during both deposition processes, the argon assist or plasma plays a definitive role in the growth production. Argon inclusion has been shown to improve the density of films because of the argon bombardment transferring momentum to the substrate, thus enhancing surface mobility.…”