Effect of micromorphology on transport properties of Nb-doped anatase TiO_2 films: A transmission electron microscopy study

摘要

We investigate the transport properties and micromorphology of polycrystalline Nb-doped anatase TiO_2 (TNO) transparent conductive films, as a function of working pressure (p_w) 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 p_w of 1 Pa showed an inhomogeneous micromorphology and a substantially low Hall mobility (μ_H) of However, films deposited at a low pw of 0.75 and 0.5 Pa exhibited less inhomogeneity in the micromorphologies and a high μ_H of 3.8 and 9.2 cm~2V~(-1) s~(-1), respectively. These results indicate that the inhomogeneous micromorphology acts as an additional carrier scattering source. The p_w dependence of the micromorphology demonstrates that the inhomogeneous micromorphology originates from density fluctuation rather than sputter damage. The working pressure (p_w) of sputtering significantly affects the micromorphology and, thus, the Hall mobility (μ_H) of Nb-doped anatase TiO_2 (TNO) transparent conductive thin films.