Effects of negative low substrate bias voltage on the structure and properties of fluorinated amorphous carbon films synthesized by plasma immersion ion implantation and deposition

Fluorinated amorphous carbon films (a-C:F) were fabricated from CF4 and CH4 mixtures under different substrate bias voltage, using plasma immersion ion implantation (PIII) apparatus. Film composition and structure were characterized by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopies. Surface morphology and roughness were analyzed by atomic force microscopy (AFM). Film hardness was measured by nano-indentation. Contact angles were measured by sessile drop method to evaluate hydrophobicity. With the increase of the bias voltage, the fluorine content was gradually decreased in the film, and the film structure was transformed gradually from polymer-like to diamond-like. At the same time, hardness values progressively increased, and the film surface become smoother. However, evident improvements of hydrophobic properties cannot be achieved only by the variation of the substrate bias voltage in a low range.