Layered films consisting of transparent conducting oxides, Ga-doped ZnO (GZO) and Nb-doped TiO2 (TNO), were fabricated on glass substrates and their electrical properties were investigated. As-deposited TNO/GZO films showed the mean resistivity of TNO and GZO films. Thermal annealing reduced the resistivity of these films; however, TNO/GZO films exhibited the lowest value among them. The carrier concentration and Hall mobility of TNO/GZO films increased with the reduction in electrical resistivity. The thickness dependence, annealing temperature dependence, and crystalline orientation of the TNO and GZO layers in TNO/GZO films indicated that the improvement of the electrical properties of the GZO underlayer contributed to the resistivity reduction behavior of TNO/GZO films induced by thermal annealing.

Nb-doped TiO2 (TNO) films, Ga-doped ZnO (GZO) films and TNO/GZO layered films were fabricated on glass substrates and electrical properties of TNO/GZO layered films were investigated in terms of interaction between TNO and GZO layers. By a thermal annealing in vacuum, the observed resistivity of the TNO/GZO layered films was lower than that of the single layered films fabricated and annealed at the same conditions. The resistivity reduction observed in the layered structure is not explained by the parallel connection of the TNO and GZO layers, indicating that there exists an interaction between these two layers. The TNO/GZO films with low resistivity have still been transparent.

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