Effect of the oxygen deficiency of ceramic TiO_2−x targets on the deposition of TiO₂ thin films by DC magnetron sputtering

Abstract

The sputter deposition of stoichiometric TiO 2 thin films has been investigated, in view of photocatalytic application. DC magnetron sputtering from ceramic targets in an argon/oxygen atmosphere was chosen as the deposition technique. Composite TiO 2 -Ti targets with metallic Ti fraction from 0 to 70 wt% were prepared from TiO 2 and Ti powders following a standard ceramic procedure.The influence of target composition and sputter parameters on the film composition was examined by means of optical transmission measurements, XRD and XPS. From the former, optical absorption coefficients are calculated, which are used as a measure for the films' stoichiometry. Curve fitting of the Ti 2p 3/2 photoemission line yields the composition in terms of the presence of reduced species.Upon sputtering in argon, translucent layers are obtained for targets with up to 35 wt% Ti. For higher amounts, the optical absorption coefficient a at 550 nm increases and the layers become dark. With increasing metal Ti contribution and argon flow, more reduced Ti species contribute to the Ti 2p photoemission line.In reactive sputter mode, near-stoichiometric TiO 2−x films are obtained for low oxygen mole fractions. For higher oxygen contributions, reduced Ti species are increasingly present for all targets. This reduction is ascribed to active re-sputtering of the deposited layer by O − ions and the sputter yield difference between oxygen and titanium.

Porous titanium-hydroxyapatite composite coating obtained on titanium by cold gas spray with high bond strength for biomedical applications

“…However, some small peaks appeared that were attributed to oxide titanium phases, such as rutile and anatase (TiO2) as well as TiO, although the low intensity of both peaks indicate limited amount of these phases. The formation of TiO2 phase is generally caused by spontaneous oxidation of titanium and titanium alloys in contact with air, while the appearance of TiO could be attributed to the TiO2 reduction by Ti in an oxygen deficient atmosphere [62,69].…”

Sputter Deposition Processes

“…Another solution is using conductive substoichiometric targets (e.g. TiO 2-x with x of the order of 0.2 [45]) for which only a low reactive gas flow is required, and generally the deposition process does not show a hysteresis behavior. However, substoichiometric target processing is more expensive and complicated as these targets are mostly ceramics.…”

Structural properties and surface oxidation states of sputter‐deposited TiO2−x thin films

“…[7][8][9] TiO 2−x films are widely used in various fields like solar cells, photocatalysis, sensors, photoelectrolysis, memory application, and biomedical devices. [10][11][12][13][14][15][16][17] In particular, anatase (A) phase is an extensively used material for various applications like lithium-ion batteries, filters, antireflective, and high reflective coatings and has been widely studied. 13 Further, the presence of mixed anatase-rutile (A-R) phase leads to a synergetic effect between two phases that improves the photoactivity of TiO 2−x .…”

“…In the recent years, TiO 2− x thin films have been extensively studied because of their interesting photocatalytic, optical, and electrical properties 7–9 . TiO 2− x films are widely used in various fields like solar cells, photocatalysis, sensors, photoelectrolysis, memory application, and biomedical devices 10–17 . In particular, anatase (A) phase is an extensively used material for various applications like lithium‐ion batteries, filters, antireflective, and high reflective coatings and has been widely studied 13 .…”