Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl ₄ /O ₂ /N ₂ Gas Mixtures

Low-pressure dielectric barrier discharge (DBD) TiCl ₄ /O ₂ and N ₂ plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A home- made large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15 ^o . Compared to titanium oxide films deposited in TiCl ₄ /O ₂ gas mixtures, those in TiCl ₄ /O ₂ /N ₂ gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl ₄ /O ₂ /N ₂ gas mixtures with the addition of 50% N 2 and 20% TiCl 4 is still smaller than 20 ^o, while that of undoped titanium oxide films is larger than 64 o when they are measured after one week. The low-pressure TiCl 4 /O 2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film’s fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl ₄ /O ₂ DBD plasmas at various power supply driving frequencies are presented.