Controlling the surface topology and hence the hydrophobicity of amorphous carbon thin films

Amorphous carbon films with different surface topologies were synthesized on a Si substrate by plasma enhanced chemical vapor deposition at various pressures using acetylene as a carbon precursor. The samples were characterized by scanning electron microscopy, atomic force microscopy and Fourier transformed infrared spectroscopy. The contact angles for water with the as-prepared carbon films were measured and found to vary in the range 40-145^o. The surface energies of the as-prepared carbon films have been calculated using the Owens method in the hydrophilic region for the two liquids namely water and glycerol. It was found that with the decrease of polar component of the surface energy the surface gradually became hydrophobic. The contact angle was also found to be independent of the pH of water from extremely acidic to extremely basic.