Observation of Hidden Parts of Dislocation Loops in Thin Pb Films by Means of Scanning Tunneling Spectroscopy

Local electronic properties of quasi-two-dimensional Pb(111) islands with screw dislocations different types on their surfaces were experimentally studied by means low-temperature scanning tunneling microscopy and spectroscopy in the regime constant current. A comparison topography map, maps current variation differential conductance acquired simultaneously allows one to visualize hidden parts dislocation loops under sample surface. We demonstrate that two closely-positioned opposite Burgers vectors can either (i) connect each other sub-surface loop or (ii) generate independent edge lines which run towards perimeter Pb island. In addition, we found a dislocation, does not produce outcoming loops. Screw are source non-quantized local thickness terraces, affecting properties.