The Effects of CF4 Partial Pressure on the Hydrophobic Thin Film Formation on Carbon Steel by Surface Treatment and Coating Method with Linear Microwave Ar/CH4/CF4 Plasma

In order to give hydrophobic surface properties on carbon steel, the fluorinated amorphous carbon films were prepared by using linear 2.45GHz microwave PECVD device. Two different process approaches have been tested. One is direct deposition of a-C:H:F films using admixture of Ar/CH4/CF4 working gases and the other is surface treatment using CF4 plasma after deposition of aC:H film with Ar/CH4 binary gas system. Ar/CF4 plasma treated surface with high CF4 gas ratio shows best hydrophobicity and durability of hydrophobicity. Nanometer scale surface roughness seems one of the most important factors for hydrophobicity within our experimental conditions. The properties of aC: H: F films and CF4 plasma treated a-C: H films were investigated in terms of surface roughness, hardness, microstructure, chemical bonding, atomic bonding structure between carbon and fluorine, adhesion and water contact angle by using atomic force microscopy (AFM), nano-indentation, Raman analysis and X-ray photoelectron spectroscopy (XPS).