Controllable Formation of (004)-Orientated Nb:TiO for High-Performance Transparent Conductive Oxide Thin Films with Tunable Near-Infrared Transmittance.

A niobium-doped titanium dioxide (Nb:TiO, NTO) film is a promising candidate material for indium-free transparent conductive oxide (TCO) films. It is challenging and interesting to control (004)-oriented growth to decrease resistivity. In this work, NTO films with different fractions of preferential (004) orientation (η) were controllably prepared by direct current sputtering. Notably, the direction of local-ordering of ions-packing could be adjusted by slightly changing the angle between the sputtering source and the glass substrate, which is identified as a key factor to determine the growth direction of a columnar crystal as well as the η of films. Hall effect measurements indicate that NTO films with the highest η present the lowest resistivity (6.4 × 10 Ω cm), which originates from super-high carrier concentration (2.9 × 10 cm) and mobility (3.4 cm V s). The corresponding low sheet resistance (10.3 Ω sq) makes it a potential material for commercial TCO films. We also observe that films with higher η show lower transmittance in the near-infrared region.