Correlation between sp²/sp³ Ratio or Hydrogen Content and Water Contact Angle in Hydrogenated DLC Film

Abstract

Water contact angle has been measured to indirectly assess the sp²/sp³ ratio and hydrogen content of DLCH film under post N₂ annealed treatment with O₂ content under 100 ppm. XPS spectrum is used to measure the C1s bonding type and calculate the sp²/sp³ ratio. The surface morphology of DLCH film was examined by SEM and AFM. From experimental results, it seems the surface morphology was not a critical factor on water contact angle value, at least for DLCH film. A quantitative correlation between water contact angle and sp²/sp³ ratio of DLCH film is established from which the hydrogen content can be estimated by the sp²/sp³ ratio as well as Angus equation.