Formation of carriers in Ti-oxide thin films by substitution reactions

Abstract

Conductive Ti-oxide thin films are produced using a reactive sputtering and post-annealing process. The lowest resistivity of Ti-oxide thin films (2.30 × 10–2 Ω-cm) can be achieved after annealing for 1 h at 400 °C in ambient O2. Additionally, the Hall measurement results indicate that the carrier concentration increases during the initial 1-h annealing process before decreasing during subsequent annealing. By curve fitting the Ols core-level peaks in the x ray photoelectron spectroscopy (XPS) spectrum of the annealed Ti-oxide thin films, we found that the oxygen (O) vacancy concentration monotonically increases with annealing time, which differs from the behavior of the carrier concentration regarding annealing time. This means that the O-vacancy mechanism alone cannot explain the formation of carriers in Ti-oxide thin films. By curve-fitting core-level Ti peaks in the XPS spectrum of annealed Ti-oxide thin films, a Ti3+-to-Ti4+ substitution reaction in the TiO2 phase of the Ti-oxide thin film after annealing plays the dominant role in the formation of conduction carriers. Instead of the O-vacancy mechanism, the Ti3+-to-Ti4+ substitution mechanism can explain the concentration of carriers in Ti-oxide thin films following annealing.

Preparation of SrTiO3/Bi2S3 Heterojunction for Efficient Photocatalytic Hydrogen Production

“…The Ti 2p profiles exhibit the two characteristic peaks at 458.24 and 464.1 eV attributed to Ti 2p 3/2 and Ti 2p 1/2 binding energies, respectively. This reveals that Ti is in the Ti 4+ state (Figure c) Figure d shows the O 1s core spectrum and it consists of two peaks at 529.3 and 531.5 eV due to the presence of lattice oxygen species and surface-adsorbed oxygen species, respectively.…”

Surface phenomenon of CeO2-added V2O5/TiO2 catalyst based chemical vapor condensation (CVC) for enhanced selective catalytic reduction at low temperatures

“…2, which was prepared using data from a previous paper by Cha et al [11] In the XPS Ce 3d spectra, we re-determined that V 2 O 5 -CeO 2 /CVC-TiO 2 has a larger intensity area of Ce 3+ ions than V 2 O 5 -CeO 2 /P25-TiO 2 . Liu et al [14] reported that Ti 3+ creates a free carrier (%electron) when oxidized to Ti 4+ . In addition, according to previous studies by Cha et al [13,16], the TiO 2 synthesized via CVC had a higher ratio of Ti 3+ ions and contained more free carriers, and had a clear effect on the oxide ion state of the loading material.…”

Growth and Characterization of Reactive DC Magnetron Sputtered Aluminum Titanate Thin Films

“…The core level binding energy of 74.2 eV of Al 2p suggested the occurrence of Al 3+ in oxidation state. It is to be noted that the core levels binding energies Ti 2p 3/2 and Ti 2p 1/2 were 458.2 eV and 464.0 eV respectively in DC magnetron sputtered TiO 2 films [15,16], while in DC magnetron sputtered (Ta 2 O 5 ) 0.85 (TiO 2 ) 0.15 films the binding energies were 458.7 eV and 464.3 eV [17]. The chemical composition of the asdeposited films was determined from the core level binding energy peak area and the sensitivity factors of the constituent elements of aluminum, titanium and oxygen [18].…”