Influence of doping on the photoactive properties of magnetron-sputtered titania coatings: Experimental and theoretical study

Abstract

The UCD community has made this article openly available. Please share how this access benefits you. Your story matters! (@ucd_oa) Some rights reserved. For more information, please see the item record link above. PHYSICAL REVIEW B 86, 115306 (2012) Influence of doping on the photoactive properties of magnetron-sputtered titania coatings:Experimental and theoretical study Titanium dioxide (TiO 2 ) thin films, doped with chromium (Cr) and codoped with chromium-carbon (Cr, C) and chromium-nitrogen (Cr, N) of various concentrations, were deposited using magnetron sputtering. Postdeposition thermal treatments were carried out at 450• C for 5 h to change the as-deposited amorphous coatings to their crystalline form. The crystalline phase was found to be dependent on the amount and type of dopant present. Ultraviolet-visible (UV-Vis) absorption data and band gap energies calculated by spectroscopic ellipsometry showed that, on increasing Cr concentration, a shift of the absorption edge towards visible light and a reduction of the band gap occurred. This was further improved by codoping of Cr with either N or C, with the latter case exhibiting more photo-activity towards visible light. In addition, hybrid density functional theory (DFT) calculations were performed for Cr-, N-. and C-monodoping, together with Cr-C and Cr-N codoping, in both rutile and anatase phases of crystalline titania. Using this method, absorption coefficients and band gaps were determined to explore photo-activity. Very good, semiquantitative agreement was found between the DFT and experimental approaches for these quantities, underlining the key role of state-of-the-art quantum calculations in interpreting and guiding experimental studies of doping in metal oxides.

Photo-active and optical properties of bismuth ferrite (BiFeO3): An experimental and theoretical study

“…McDonnell et al [34], both with an exact-exchange contribution of 25%. However, in this study we "tune" the exact-exchange contribution parameter "α" in eqn.…”

“…PBEsol has been used due to its superior geometry prediction vis-à-vis PBE exchange-correlation in solids [32,33] leading to more accurate Born-Oppenheimer forces acting on the electronic wave-functions, and providing the best feasible estimation of electronic properties. To avoid the expensive calculation of long-range HF exchange, this term is replaced by long-range PBEsol exchange; details are inferred in the earlier work [34].…”

The influence of Ti- and Si-doping on the structure, morphology and photo-response properties of α-Fe2O3 for efficient water-splitting: Insights from experiment and first-principles calculations

“…PBEsol has been used due to its superior geometry prediction vis-à-vis PBE exchange-correlation in solids [21,22] leading to more accurate Born-Oppenheimer forces acting on the electronic wave-functions, and providing the best feasible estimation of electronic properties. To avoid the expensive calculation of long-range HF exchange, this term is replaced by long-range PBEsol exchange; further details may be obtained from earlier work applied to photovoltaic properties of titania [23]. In any event, this choice of parameters for HSE06-PBEsol is identical to the recent work of Schimka et al [24], who have found that this works well for a range of solids, and also of McDonnell et al [23], both with an exactexchange contribution of 25%.…”

“…To avoid the expensive calculation of long-range HF exchange, this term is replaced by long-range PBEsol exchange; further details may be obtained from earlier work applied to photovoltaic properties of titania [23]. In any event, this choice of parameters for HSE06-PBEsol is identical to the recent work of Schimka et al [24], who have found that this works well for a range of solids, and also of McDonnell et al [23], both with an exactexchange contribution of 25%. However, it is also possible to change the proportion of exact exchange to tailor the band-gap and optical properties for optimal agreement with experiment; for instance, 10% proportions were used in recent work for bismuth-containing compounds [25,26].…”

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

“…Hydrogen, boron, carbon, nitrogen, fluorine, iodine, sulfur, and phosphorus have been used in this capacity, but nitrogen has been studied most extensively. Until now, various approaches to incorporate nitrogen atoms into titania have been reported, such as doping during film sputtering [131], annealing under ammonia gas [12], ion implantation [132,133], hydrazine treatment [134][135][136], urea treatment [137][138][139], treatment of sol-gel titania with nitrogen-containing organics [140], electrochemical processing [141], chemical vapor deposition [142], and plasma techniques [11,13,35,[143][144][145][146][147][148][149][150]. Most of the above doping methods require high temperature treatment and complicated or expensive equipment.…”