Plasma surface fluorination of ultrananocrystalline diamond films

Ultrananocrystalline diamond films have been subjected to CHF3 and SF6 rf plasmas in order to achieve a fluorine terminated surface. Major parameter varied in this study was besides the nature of the process gas the exposure time. The treated surfaces have been investigated by contact angle and atomic force microscopy measurements; X-ray photoelectron spectroscopy has been used to determine the surface composition and to get insight into the bonding environments of the treated surfaces. Both plasma treatments lead to similar results. The surfaces are fluorinated by fluorine containing groups, namely CF, CF2, and CF3, with F concentrations of about 20%. This leads to high contact angles of 95-110 degrees; the surfaces are slightly etched and became somewhat smoother. Nevertheless, there are distinct differences between the surface obtained by the CHF3 and SF6 treatments, respectively, the nature of which will be discussed in this paper, together with the underlaying mechanisms. (C) 2016 Elsevier B.V. All rights reserved.