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| Home > Publications database > Spektroskopische Untersuchung des Zustandes von Helium in Blasen in Aluminium und Nickel |
| Book/Report | FZJ-2018-01945 |
1982
Kernforschungsanlage Jülich, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/17708
Report No.: Juel-1814
Abstract: The physical state of helium in small bubbles in aluminium and nickel films (500 - 1000 $\mathring{A}$ thick) with average He concentrations between 1 and 30 at .%has been investigated by transmission electron energy-loss spectroscopy (EELS) with 50 and 200 KeV electrons using a new UHV-spectrometer, transmission electronmicroscopy (TEM), and proton . The proportionality factor is (24 $\pm$ 5) $\mathring{A}^{3}$ eV. The maximum He density has been observed in the smallestbubbles with diameter of about 10 ~ . We found a maximum density of (0.14 $\pm$ 0.03) $\mathring{A}^{3}$ in Al and up to 0.20 $\mathring{A}^{-3}$ in Ni which is 10 times as high as the density of liquid He at 4.2 K and 1 bar. Using an equation of state for extremely dense He these densities correspond to He pressures in thebubbles of 130 Kbar in Al and 500 Kbar in Ni. These values are close to the limits of the material strength of the metals. Applying the relation between $\Delta$E and n on the dose and temperature dependence of the He 1S-2P transition shows that during room temperature implantation bubble nucleation in Al takes place predominantly for He concentrations C$_{He}$ < 6 at .%. In excess of 6 at .% the bubble concentration decreases rapidly with increasing C$_{He}$ indicating the onset of bubble migration and coalescence. In the annealing temperature range 20°C < T < 200°C the He bubbles grow by emission of interstitial loops while for T > 200°C bubble growth is controlled by thermal vacancy absorption. In addition plasmon excitations on the bubble surfaces in Al have been investigated. Excitation eigenmodes with 1 > 1 have been observed for the first time.
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