W. Vollenberg

Study of the discharge gas trapping during thin-film growth

Discharge gas trapping in thin films produced by sputtering is known to be due to high-energy neutrals bouncing back from the cathode. Qualitatively, the phenomenon is enhanced by raising the discharge voltage and is strongly dependent on the atomic masses of the discharge gas and of the cathode material. In addition to these known effects it is shown that, for a given gas, the trapped amount decreases with increasing melting temperature of the deposited material. The results obtained both by sample melting and laser ablation are presented and discussed.

Phase transition study of superheated planar arrays of tin cylinders

Abstract We have investigated the superheating and the supercooling fields of a planar array of tin cylinders with diameters ranging from 40 to 80 μm and thickness 8.3 μm evaporated onto a glass substrate and onto a kapton foil. Experimental values of the Ginzburg–Landau parameter have been obtained and compared with results from tin spheres. The spread of the superheating curves is below 5%.

Improvement of the phase transition homogeneity of superheated superconducting tin granules

Abstract A considerably improved phase transition homogeneity was observed with superheated superconducting Sn spheres as a result of laser melting and fast cooling. These spheres exhibited a very homogeneous phase transition behaviour independent of the orientation of the spheres with respect to the direction of the external magnetic field. Compared to previously untreated Sn spheres the spread of the phase transition boundaries was reduced by almost an order of magnitude. In addition, we studied mass production of Sn structures using vacuum evaporation and deposition. First encouraging results are reported.