Deuterium plasma exposure of thin oxide films on tungsten - oxygen removal and deuterium uptake

•Intact WO3/W interfaces prevent deuterium (D) uptake into metallic tungsten (W).•55 nm thick oxide: Interface is stable during D plasma exposure at 5 eV/D; 370 K.•Reduction increases strongly at higher temperature (500 K) or D energy (38 eV/D).•D uptake into W increases with area fraction of (partially) reduced interface.•Native W oxide may affect D uptake in laboratory studies but not in fusion reactors.