Visible Light Photocatalysis of Nitrogen-Doped Titanium Oxide Films Prepared by Plasma-Enhanced Chemical Vapor Deposition

N-doped films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using titanium tetraisopropoxide and mixture. Two nitrogen bonding states, substitutional and interstitial nitrogen atoms, are observed and about 80% of nitrogen atoms exits the substitutional sites irrespective of nitrogen content. The transition temperature from the anatase to rutile becomes lower in the N-doped films compared with that of nondoped films. Visible light photocatalysis, both photocatalytic decomposition of organic compounds and photoinduced hydrophilicity, was observed in the N-doped films. It is considered that both nitrogen atoms substituted for oxygen atoms and crystalline structure contribute to the visible-light photocatalytic activity.