SiOx plasma thin film deposition using a low-temperature cascade arc torch

Plasma thin films were deposited from gas mixtures of hexamethyldisiloxane (HMDSO) and oxygen (O2) using a low-temperature cascade arc torch (LTCAT). Various properties of the deposited HMDSO plasma coatings, including refractive index (RI), surface contact angle, and hardness were evaluated. The characterization results using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, ellipsometry, and water contact angle measurements indicated that, with increased O2 addition, the deposited HMDSO plasma thin films were of inorganic SiOx nature. It was also found that, in the LTCAT plasma system, O2 addition significantly improves the hardness of the resulting HMDSO plasma coatings. The film hardness of the deposited HMDSO plasma coatings measured by a standard pencil test (ASTM D3363-05) reached 6H with increased O2 addition in the HMDSO/O2 gas mixture. Such hard plasma coatings could be potentially used for many important industrial applications, such as anti-scratch coatings on plastic glasses and various plastic lens materials.