Fluorination of polycrystalline diamond films and powders. An investigation using FTIR spectroscopy, SEM, energy-filtered TEM, XPS and fluorine-18 radiotracer methods

Abstract

Polycrystalline diamond films and diamond powders, treated with elementary fluorine, chlorine trifluoride or anhydrous hydrogen fluoride under various conditions, have been examined using spectroscopic and microscopy techniques. Formation of C–F bonds occurs when F₂ or ClF₃ are used, the surface groups present being tentatively identified from XPS and FTIR measurements. Surprisingly, the interaction between HF and diamond is substantial and its extent has been quantified using fluorine-18 labelling. Hydrogen fluoride deposited on diamond is labile with respect to exchange with H¹⁸F and undergoes slow hydrolysis on exposure to moist air. This treatment, therefore, results in an unusual hydrophilic surface. In contrast, there is no observable [¹⁸F] exchange between F-terminated diamond and HF.