Pilot experiments on In atoms softlanded on Cu(100)

We performed a number of experiments to determine the properties of the soft-landing ion beam and to characterise the produced samples. In above figure we plotted the ion current as function of the potential difference between the ion source and the target, for different atomic species and ion discharge currents. The ion current has been normalised to the unretarded ion beam. The data are used to estimate the deposition energy of the softlanded ions, assuming that zero transmission corresponds to a deposition energy of 0 eV. According to these data, the plasma potential in the ion source is approximately 5 - 10 eV higher than the discharge potential over the plasma.

It turned out that the exact value of this excess potential is very sensitive to the ion source conditions. For exemple, a decrease of the axial magnetic field applied over the ion plasma from 150 to 50 G, results in an increase of the excess potentiel from 3 to 18 V (see next figure).

The homogeneity of a thin In overlayer on Cu(100) was checked with RBS, indicating that (see figure)

• the layer thickness agrees within 20% with the number of deposited In ions
• the layer thickness varies less than 20% over the beam spot
• the size of the beam spot is about 0.5 cm²

The chemical purity of the deposited material is very good. From the Auger spectrum shown above we calculate impurity concentrations of < 0.03 ML C, < 0.02 ML O and < 0.01 ML Cl.