Structural properties and surface oxidation states of sputter‐deposited TiO_2−x thin films

Abstract

Titanium dioxide (TiO2−x) films were deposited on silicon (100) substrates from pure titanium (Ti) targets using direct current magnetron sputtering technique. TiO2−x thin films were grown in the thickness range of 515–672 Å with varying sputter powers of 75 and 100 W, at both room temperature (RT) and 200°C substrate temperature (Ts). Structural and compositional characterization of the films, which included surface morphology and study of surface chemical states, was performed. The influences of sputter power and substrate temperature on these parameters were specifically analyzed. Grazing incidence X‐ray diffraction showed that the thin films were amorphous at RT and crystallinity could be achieved only at Ts. The latter showed anatase phase at sputter power of 75 W and transformed into anatase–rutile mixed phase at 100 W. The thickness, roughness, and mass density of the thin films were measured using X‐ray reflectivity. It was observed that for Ts films, the roughness and mass density increased with higher sputter power. Field emission scanning electron microscopy and atomic force microscopy also corroborated this surface roughness result. It was observed from X‐ray photoelectron spectroscopy that the core levels of Ti‐2p3/2 and O‐1s and their corresponding binding energies indicated that only one of the Ti oxidation states, i.e., Ti4+, existed in the films. This work provides insight about the growth of TiO2−x thin films influenced by Ts deposition and different sputter power.

Effect of substrate temperature and annealing on the growth of TiO2‐x thin films deposited by using DC‐magnetron sputtering technique

“…The films deposited with sputter powers of 75 and 100 W for 10 and 7 min, respectively; a detailed description of this technique can be seen in our earlier publication. 20 Afterwards, the films were held under a vacuum of 10 À4 Pa in a high vacuum tube furnace (in-house built) while being annealed at 300, 400 and 500 C. Initially, a vacuum pump was used to evacuate the vacuum tube furnace. After that, the heater was put on at a rate of 10 C per min.…”

“…The spectrometer was standardised by fixing the binding energy of the Au-4f7/2 line at 84.0 eV prior to data acquisition. 20 In order to get more information, the GIXRD patterns of the TiO 2-x films were annealed at 300, 400 and 500 C for both films deposited at RT and ST.…”

“…15 It also depends on the plasma parameters (such as particle densities, discharge current, electron and ion energy distributions and deposition rate), target-substrate distance, substrate temperature (ST), reaction atmosphere and the geometrical configuration of the system. [16][17][18][19] In a previous study, 20 we have shown that TiO 2-x films deposited with different sputter powers (75 and 100 W) at room temperature (RT) and 200 C ST have good quality, homogeneity and roughness.…”

“…The argon pressure used for the deposition was relatively high (1.2 Pa), and no external oxygen source was used. 20 The impact of annealing on the nanostructure characteristics of TiO 2-x thin films formed on Si by DC-magnetron sputtering deposition without the presence of oxygen has received little attention in the literature. It is anticipated that thermal annealing could be very important for structural modification of the films by forming polycrystalline structures with different grain sizes and crystallographic preferred orientations.…”

Plasma‐deposited AgOx‐doped TiOx coatings enable rapid antibacterial activity based on ROS generation

“…As seen in Figure 2c, plasma oxidation produced a distinct defective TiOx film (also named TiO 2 − x ) characterized by a high amount of Ti 3+ (accompanied by O vacancies) besides Ti 4+ (TiO 2 ) with a lower metallic character than the nonoxidized reference. [21,22,50] The selected amount of Ag as dopant on the TiOx support thus provides a promising catalyst with a large interface area between the oxidized Ag nano islets and the defective TiOx.…”