Semiconducting behavior of niobium-doped titanium oxide in the amorphous state

Electrical properties of Nb-doped titanium oxide films were evaluated with respect to annealing temperatures. Although an amorphous phase is preserved up to 450°C, x-ray absorption spectroscopy analyses indicate that crystal field splitting in the conduction band begins to take place at this temperature. Such molecular orbital ordering effects induce a semiconducting behavior, which is manifested by working thin film transistor devices with field effect mobility values as high as 0.64 cm ²/Vs. X-ray photoelectron spectroscopy studies disclose a drastic increase in Nb ⁺⁵ states upon heat treatment, and these may be attributed to oxygen deficient states that generate free electrons.