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 O-2 and N-2 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 10(18) and 10(19) 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 O-2 and N-2 flow rates reached 100% at wavelengths longer than 1000 nm. However, complete termination of Ti with N atoms failed to occur at low O-2 flow rates even when the N-2 flow rate was increased. The carrier concentration (n) of the TiON films could be varied in a wide range between 10(18) and 3 x 10(21) cm(-3). The n (x10(-19) cm(-3)) versus Hall mobility (mu) (cm(2) V-1 s(-1)) plot scaled as log mu = 1.23 - 0.38.log n between 1 x 10(18) and 1 x 10(20) cm(-3). The Hall mobility reached 20-50 cm(2) V-1 s(-1) at n = 10(18) cm(-3), which means this film is promising as an amorphous semiconductor. The log-log plot of resistivity (rho) (m omega cm) against n scaled as log rho = 1.74 - 0.87.log n.

Automated summary

This study investigated the characteristics of titanium oxynitride thin films. The films transformed from nanocrystalline to amorphous structure as the degree of oxidation and nitridation increased. The oxidation efficiency was higher than the nitridation efficiency. Under appropriate gas flow conditions, the films exhibited high optical transmittance. There was a logarithmic relationship between the carrier concentration and Hall mobility of the films.