Fluorination of Copper Surface and ESCA Study

The fluoride film on copper surface fluorinated by fluorine gas and anode polarization in hydrogen fluoride solution has been studied by means of X-ray photoelectron spectroscopy, Xray diffractometry and scanning electron microscopy. The fluoride film is mainly composed of CuF2 containing oxygen species such as Cu2O. The films adsorbs oxygen and moisture on exposure to air and results in the formation of CuF2[sm middot]2 H2O, which changes the transparent film to black. ESCA study shows that more oxygen than stoichiometry is included on the surface of the fluoride film. The ratio of O/Cu increases and that of F/O decreases when it is exposed to air. The fluorine species in the film is dissolved as fluoride ion when a sample is immersed into water, acid or basic solution. Under the condition of ESCA measurement, CuF2 film is not reduced by X-ray irradiation but is reduced by Ar+ ion bombardment.