Optical properties of amorphous fluorinated carbon films prepared by electron cyclotron resonance plasma

The optical property of amorphous fluorinated carbon (alpha -C: F) films ar e investigated, which are prepared by microwave electron cyclotron resonanc e ( ECR) plasma chemical vapor deposition ( CVD) using trifluromethane ( CH F3) and benzene (C6H6) as source gases. The optical energy gap E-g of the a lpha -C:F films deposited at 140-700W powers and CHF3 : C6H6 = 1: 1-10:1 ar e between 1.76 and 2.85eV. The amount of fluorine in the films has an effec t on optical absorption and energy gap The absorption edge increases as the amount of fluorine is raised. The optical energy gap E-g is mainly determi ned by CF bond in the films, which results in the change of the density of states in band tail of the valence band.