Properties of Ion Beam Deposited Tetrahedral Fluorinated Amorphous Carbon Films (ta-C:F)

Abstract

ABSTRACTWe have studied the growth and the properties of ta-C:F films prepared by the deposition of mass separated 12C+ and 19F+ ions as a function of the F concentration CF. The films are always strongly F-deficient due to the formation of volatile CFx, molecules during the deposition process. CF ≈ 25 at.% is obtained for an ion charge ratio of C+:F+ = 1:1. The mass density strongly decreases from 2.9 g/cm3 for ta-C to 1.1 g/cm3 for films with CF ≈ 23 at.%, whereas the electron density related plasmon energy only varies slightly between 31.8 eV and 29 eV. Therefore, films with small CF have both a high mass and high electron density resulting in diamond-like properties. The discrepancy between low mass density and high electron density for films with large cF can be explained by voids. The thickness and composition of films with CF below 20 at.% remains unchanged for vacuum annealing to temperatures of 600 °C for 10 minutes. Loss of F was observed for films with cF above 20 at.%. The compressive film stress decreases with increasing CF, and is further reduced by annealing.