Synthesis of model sodium sulfide films

We report the direct deposition of model sodium sulfide films by RF magnetron sputtering from Na2S and Na2S2 deposition targets. Analytical characterization and electrochemical cycling indicate that the deposited films are amorphous with stoichiometries that correspond to Na2S3 and Na2S2 formed from the Na2S and Na2S2 targets, respectively. We propose that the loss of Na in the case of the Na2S target is due to preferential sputtering of Na resulting from the higher energy required to break the Na–S bonds in Na2S. The development of thin film sodium sulfides opens a new route to understanding their fundamental properties, such as Na⁺ transport, conductivity, and reactivity.