Diffusion Behavior of Cumulative He Doped in Cu/W Multilayer Nanofilms at Room Temperature**Supported by the National Natural Science Foundation of China under Grant Nos 11275132, 51171124 and 11505121, the International Science and Technology Cooperation Program of China under Grant No 2014DFR50710, and the Scientific and Technical Supporting Programs Funded by the Science and Technology Department of Sichuan Province under Grant

Abstract

Cu/W multilayer nanofilms are prepared in pure Ar and He/Ar mixing atmosphere by the rf magnetron sputtering method. The cross-sectional morphology and the defect distribution of the Cu/W multilayer nanofilms are characterized by scanning electron microscopy and Doppler broadening positron annihilation spectroscopy. The results show that plenty of point defects can be produced by introducing He during the growth of the multilayer nanofilms. With the increasing natural storage time, He located in the near surface of the Cu/W multilayer nanofilm at room temperature could be released gradually and induce the segregation of He-related defects due to the diffusion of He and defects. However, more He in the deep region spread along the interface of the Cu/W multilayer nanofilm. Meanwhile, the layer interfaces can still maintain their stability.