Optical brazing technique for bonding diamond films to zinc sulfide

摘要

Diamond films can be used as infrared-transmittance protective coatings on ZnS. However, a direct deposition of diamond films on ZnS by chemical vapor deposition has been proved to be impossible. One effective method to realize this application is to bond diamond film with ZnS by optical brazing, in which the chalcogenide glass (Se-As-S) is used as adhesive. In this paper, the diamond films were prepared by microwave plasma-enhanced chemical vapor deposition. The adhesive films were deposited on ZnS (or on diamond film) by evaporation. To our knowledge, this is the first time to report this method. It was found that the thickness of the adhesive can be easily controlled and the diamond films were conveniently bonded to ZnS plates having different sizes. A 76-mm diameter diamond film was successfully bonded to ZnS by the present technique. The bonded optical disk showed good adhesion and infrared transmittance. The average transmittance is over 67% in the interested infrared wavelength range from 8 to 12 #mu#m. The influence of bonding temperature and chalcogenide film thickness on the transmittances of the bonded structure are investigated.