Interaction of energetic oxygen ions with the beryllium tungsten alloy Be2W

In this study, the interaction of energetic oxygen ions with the beryllium tungsten alloy Be2W is investigated by depth resolved x ray photo electron spectroscopy. A 4 nm tungsten layer is deposited on polycrystalline beryllium. By alloying at 900 K for 60 min, Be2W is formed. In successive steps, oxygen ions are implanted with 500 and 1000 V acceleration voltage with a fluence of 5 x 10 14 cm 2 in each step. Between the single implantation steps the sample is heated for 30 min at 600 K. Depth resolved photoelectron spectroscopy is performed after each experimental step. The W 4f and Be 1s spectra reveal the formation of berylliumtungstate BeWO4 already at room temperature RT in significant amounts due to energy deposition of implanted oxygen ions. No indication of oxygen diffusion at RT is observed. In previous experiments in thermal equilibrium, the ternary compound has proven to be stable at temperatures up to 1073 K. Contrary to these results, annealing at 600 K leads to decomposition of the BeWO4 formed by energetic oxygen ions. After decomposition at 600 K, oxygen stays in the sample bound as Be