Reactive Twin-magnetron Sputtering of Ti_(1-x)Nb_xO_2 Transparent Conducting Oxide Films

摘要

We obtained Ti_(1-x)Nb_xO_2 (TNO) by doping Nb to TiO_2. TNO transparent conducting film was fabricated by reactive mid-frequency (MF) twin-magnetron sputtering method with assistance of a multicell anode layer ion sources, and the sputtering process was controlled by plasma emission monitor (PEM). The films were characterized by Xray diffraction (XRD), atomic force morphology (AFM), spectroscopic ellipsometry, spectrophotometer and xray photoelectron spectroscopy (XPS). The behaviors of the carrier concentration and mobility of TNO thin films were investigated by means of the Hall technique. The results demonstrate that the reactive process can be controlled stably during the metaloxide transition with monitor of PEM, and the disadvantages of titanium target poison and anode disappear were also successfully overcome. Polycrystalline TNO thin films with 0.03 ≤x≤0.06 show a resistivity (ρ) of lower than 2.0×10~3 Ωcm, and internal optical transmittance higher than 90% at 600 nm. The first-principle band calculations demonstrate that Ti2p, Nb3d and Ti3d states are strongly hybridized with each other to form nature conduction band, substituted Nb atoms are ionized and release electrons into the hybridized conduction band without forming midgap state.