Abstract
Reduced titania phases such as Ti2O3, Ti3O5, and TixO2x-1 (the magńeli phase, 4 ≤ x ≤10) are collectively a promising class of materials due to the stoichiometric tunability of their electronic structure. This flexibility, combined with their relatively high electrical conductivity, high corrosion resistance, and photostability makes reduced titania a candidate for many applications. In this work, stable reduced titania films were synthesized on silicon substrates via pulsed laser deposition (PLD) under a forming gas environment at elevated temperatures. The atomic/electronic structure and the electrical properties of the PLD reduced titania films were investigated using four-point probe, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy (XAS), and ultraviolet photoelectron spectroscopy (UPS). The PLD films demonstrated a notable decrease in resistivity compared to those of stoichiometric TiO2 films reported in the literature. Raman spectroscopy and XAS revealed that the observed resistivities in these films are correlated to substoichiometric titania phases (Ti2O3 between 400-600 °C and the Ti3O5-like at 700 °C) present in them. UPS measurements on the sub-stoichiometric titania indicated a decrease in the work functions with a decrease in the titanium oxidation state. The ability to tune such electrical properties with careful control of preparation is key to using reduced titania as a flexible platform for material design.
