LASER TREATMENT OF DIAMOND FILMS

Diamond thin films promise excellent performance in several applicatio n fields such as high-temperature and high-frequency electronics, prot ective coatings for components exposed to aggressive ambient condition s, and electrode materials in electrochemistry. However, these interes ting perspectives are presently limited by the polycrystalline morphol ogy of deposited films that include a noticeable surface roughness and the presence of pinholes. The objectives of this work are to get a de eper understanding of the interactions and effects of intense radiatio n on wide band gap materials, and to explore the conditions that may b etter smooth the surface roughness and fill the pinholes. A comparison is made between the effects induced on HF-CVD deposited diamond films by radiation of energy values larger (ArF, lambda = 193 nm, h nu cong ruent to 6.4 eV) and smaller(Nd:YAG, lambda = 532 nm, h nu congruent t o 2.3 eV) than the electronic energy gap (h nu congruent to 5.4 eV). T hese are analyzed by SEM and Raman spectroscopy. The radiation of the Nd:YAG laser leaves the diamond thin film largely unaffected and is hi ghly absorbed by the silicon substrate. The ArF laser radiation, on th e other hand, shows a much larger absorption, probably associated with an electronic transition from the valence band to the vacuum, which c annot be performed at first order by electronic transitions induced by Nd:YAG radiation. (C) 1998 Elsevier Science B.V.