Preservation and Release Dose of Helium Implanted in Nanocrystal Titanium Film

Helium concentration profile, preservation dose and release rate from a nanocrystal titanium film implanted with helium at an energy of 100 keV and dose of 2.2×1018 cm-2 are measured by proton Rutherford backscattering technique in a range from room temperature to 400 ℃. The implanted helium may be stably preserved up to the 68 percent after keeping a long time of 210 d in the nanocrystal titanium film at the room temperature environment, and the HeTi atomic ratio reaches to 52.6%. When the temperature of specimen increases to 100 ℃, the helium concentration can be preserved to 89.6% of the keeping helium dose at room temperature and HeTi atomic ratio reaches 44%. Even if the specimen temperature up to 400 ℃, the helium concentration still can be preserved to 32.6% of the keeping helium dose at room temperature and the HeTi atomic ratio is 17.1%. Possible mechanism of helium effectively preserved in the nanocrystal titanium film is discussed based on the energy stability viewpoint.