Modification of YBa2Cu3O7-δ wires using a scanning tunneling microscope:: Process and electrical transport effects

Wires of the high temperature superconductor YBa2Cu3O7-delta (YBCO) were fabricated by electron beam lithography and were subsequently modified further on a sub-100 nm scale using the scanning tunneling microscope (STM). The process responsible for this modification has been shown to be field enhanced corrosion of the YBCO surface in the presence of CO2 and H2O. The intention of this work is to investigate the effect of the STM induced modifications on the electrical transport behavior of the YBCO wires with current-voltage characteristics (CVCs) measured at 77 and 4.2 K. Different types of CVCs can be distinguished, depending on the size of the cut into the wire generated by the STM. The measured characteristics will be explained by thermal self-heating at locations of the wire induced by the STM. Thus, the STM modifications initiate thermal domains in the wire where the Joule heat emission generated at sufficient high current values raise the temperature of the wire above its critical temperature. Furthermore, a steplike structure in the CVC of a STM fabricated nanobridge is detected, which we attribute to an increase of the number of vortex trajectories as the transport current through the wire is increased: (C) 1998 American Vacuum Society. [S0734-211X(98)04706-4].