Transparent conductive properties of TiON thin films

Titanium oxynitride (TiON) thin films were deposited on glass substrates by reactive sputtering of a Ti target under a flow of O2 and N2 gases. When the total number of O and N atoms bonded to Ti was small, the TiON films took on a nano-crystalline fcc structure primarily oriented toward the (200) direction. As the TiON films became more oxidized and/or nitrided, they gradually transformed into an amorphous state with their carrier concentration being between 1018 and 1019 cm−3. The efficiency of oxidization was six times higher than that of nitridation. The optical transmittance of TiON films deposited at RT under sufficient O2 and N2 flow rates reached 100% at wavelengths longer than 1000 nm. However, complete termination of Ti with N atoms failed to occur at low O2 flow rates even when the N2 flow rate was increased. The carrier concentration (n) of the TiON films could be varied in a wide range between 1018 and 3 × 1021 cm−3. The n (×10−19 cm−3) versus Hall mobility (μ) (cm2 V−1 s−1) plot scaled as log μ = 1.23 − 0.38⋅log n between 1 × 1018 and 1 × 1020 cm−3. The Hall mobility reached 20–50 cm2 V−1 s−1 at n = 1018 cm−3, which means this film is promising as an amorphous semiconductor. The log–log plot of resistivity (ρ) (mΩ cm) against n scaled as log ρ = 1.74 − 0.87⋅log n.