Effect of micromorphology on transport properties of Nb‐doped anatase TiO2 films: A transmission electron microscopy study

We investigate the transport properties and micromorphology of polycrystalline Nb‐doped anatase TiO2 (TNO) transparent conductive films, as a function of working pressure (pw) during sputtering. The TNO films were crystallized from amorphous precursors sputter‐deposited on unheated glass substrates. The micromorphologies of the TNO films were observed using a transmission electron microscope. The film deposited at a high pw of 1 Pa showed an inhomogeneous micromorphology, and a substantially low Hall mobility (μH) of 2.0 cm2V−1s−1. However, films deposited at a low pw of 0.75 and 0.5 Pa exhibited less inhomogeneity in the micromorphologies and a high μH of 3.8 and 9.2 cm2V−1s−1, respectively. These results indicate that the inhomogeneous micromorphology acts as an additional carrier scattering source. The pw dependence of the micromorphology demonstrates that the inhomogeneous micromorphology originates from density fluctuation rather than sputter damage. The working pressure (pw) of sputtering significantly affects the micromorphology and, thus, the Hall mobility (μH) of Nb‐doped anatase TiO2 (TNO) transparent conductive thin films.