Influence of Helium-Related Defects on Hydrogen Retention in Nano-Polycrystalline Tungsten Films

The influence of helium-related defects on hydrogen retention in magnetron sputtered nano-polycrystalline tungsten films,which had been sequentially irradiated by high energy helium and hydrogen ions,was investigated by means of X-ray diffraction(XRD),scanning electron microscope(SEM),elastic recoil detection(ERD) and slow positron beam analysis(SPBA).The results show that the helium ion implanted tungsten films would transform from β-W to α-W after annealing.After annealing at 873 K the release of helium atoms increased dramatically,while the open- volume defects and the degree of structural disorders in the films increased.Furthermore,the total retention of hydrogen in tungsten films decreased slightly with the decreasing of helium content.