Niobium doped TiO2: Intrinsic transparent metallic anatase versus highly resistive rutile phase.

We report on the structural, electrical, and optical properties of 5% niobium doped TiO₂ thin films grown on various substrates by pulsed laser deposition. The epitaxial anatase Nb:TiO₂ film on LaAlO₃ is shown to be an intrinsic transparent metal and its metallic property arises from Nb substitution into Ti site as evidenced by the Rutherford backscattering channeling result. In contrast, the rutile Nb:TiO₂ thin films show insulating behaviors with 2–3 orders higher room temperature electrical resistivity and ∼30 times lower mobility. A blueshift in the optical absorption edge is observed in both phases, though of differing magnitude. [ABSTRACT FROM AUTHOR]