An investigation of Li-bearing Cu--Ag, Cu--Ti, and W--Al--Ti thin films deposited by ion-beam sputtering and ion plating

The development of erosion resistant thin films for magnetic fusion device applications is investigated using ion-beam sputter deposition and ion plating techniques for fabricating Li-bearing thin films on stainless steel substrates. Ion-beam sputter deposition was performed using bulk targets consisting of Cu--Li--Ag, Cu--Li--Ti, and W--AlLi--Ti for selected substrate temperatures. Ion plating was also used to deposit Cu and Ti/Cu films on stainless steel substrates. The deposited films were then heat-treated in Li atmosphere at various temperatures for producing Li-bearing films. Analyses of Auger electron spectra have revealed that ion-beam sputter deposited Cu--Li--Ti and Cu--Li--Ag films contain approximately 18 at. % Li, being uniform throughout the thin film and almost equal to the bulk Li concentration (22 at. %) of the respective target materials. Subsequent heating of the Cu--Li--Ti films indicates Li segregates to the surface forming a regenerative Li overlayer. In the case of ion-beam sputter deposited W based films, the presence of Li in the films has been detected by the sputter neutral mass spectroscopy. The ion-plated/Li-treated Cu and Cu/Ti thin films have been shown via Auger profiling to contain 12--18 at. % Li and 8--15 at. % Li, respectively. In the case of the Cu--Ti--Li films, Li existed in the metal state when relatively large local concentration of Ti was present, while Li predominantly exists as an oxide in Ti-deficient regions of the film