Control of the optical and crystalline properties of TiO2 in visible-light active TiO2/TiN bi-layer thin-film stacks

Abstract

Multi-layered thin films of TiO2 and TiN were created by rf reactive magnetron sputtering, and their crystalline, optical, and photoelectrochemical properties were measured. The overall composition of the films (TiO2-to-TiN ratio) was kept constant with the height of each film. The number of layers and thickness of each layer was controlled to create bi-layer thin films that were composed of: 9 bi-layers, 18 bi-layers, 27 bi-layers, 36 bi-layers, and 45 bi-layers. XRD patterns were observed for each film after annealing to measure the grain size and composition of anatase and rutile as a function of temperature. It was found that the phase-transition temperature is able to be substantially controlled (between 550 °C and 850 °C) for the anatase to rutile transition by varying the number of layers/thickness of each layer. In addition, bi-layer stacking significantly affected the film’s optical properties by lowering the bandgap into the visible-light region, and also showed up to three times the improvement in photoelectrochemical performance under uv and visible irradiation. Overall, bi-layer stacking of TiO2/TiN films has shown a unique and highly desirable control over several important physical characteristics that can be beneficial for many applications, such as high-temperature sensors and optoelectronic devices.

Enhanced visible light photoactivity and charge separation in TiO2/TiN bilayer thin films

“…As discussed by A. Fujishima and K. Honda [44], the photo-induced oxidation reactions at TiO 2 surfaces are mainly due to water splitting and the value of photocurrent can therefore be directly related to the kinetics of O 2 generation. multistack is still more efficient to generate higher photocurrent than the 9 bilayers under white light (UV) as well as visible light irradiation, which is consistent with our previous results [17]. The 18 bilayers could generate a photocurrent up to 2.5 times higher than that generated by the 9 bilayers.…”

“…In this study, we optimized a unique organization of TiO 2 /TiN bilayer thin films that show significant enhancement in visible light photocurrent generation and photocatalytic activity compared to similar films made in a previous work [17]. Films were deposited with 9 bilayers, and 18 bilayers having all the same total height (500 ± 50 nm) and with different thicknesses of the TiN and TiO 2 layers.…”

Improved osteoblast compatibility of medical‐grade polyetheretherketone using arc ionplated rutile/anatase titanium dioxide films for spinal implants

“…One shall however bear in mind that there might be amorphous phase coexists in the deposited film, regardless of the coating parameters, and the resultant in vitro test may synergistically be affected by the coexistence of crystalline TiO 2 structure and amorphous TiO 2 structure. Nevertheless, Smith et al 21 and Bayati et al 22 also carried out TiO 2 crystal structure composition in bilayer stacking of TiO 2 /TiN films and S-doped TiO 2 nanoporous layers and concluded that the property presents a consistency with the change in phase structure composition.…”

Tuning the optical bandgap of TiO2-TiN composite films as photocatalyst in the visible light

“…32 It could be interpreted that the film mixed with TiO 2 and TiN is an indirect semiconductor. 33 The Tauc 34 plot of (αE) 1/2 versus the photon energy (E = hν) is shown by Figure 4(c), from which the optical band gap of the films can be derived. Figure 4(d) shows the optical band gap of the films as a function of the annealing time.…”