Tunneling tips imaged by scanning tunneling microscopy

Abstract

Electrochemically etched tips commonly used for scanning tunneling microscopy (STM) have been investigated by STM itself. By appropriate positioning, the topography of the apex of the tips could be investigated, leading to a typical value for the tip radius of 300 nm. Different techniques have been attempted to untangle the convoluted STM image. By rotating one tip relative to the other, or by exchanging one tip and leaving the other in place, some distinct features can be attributed to the one or the other tip. Furthermore, the profile of the tip could be investigated by scanning over the edge of a cleaved crystal. Beside the fundamental interest in the tip structure itself, this configuration offers the unique feature of unambiguous relocation of the scanned area when the tip investigated in that experiment has been removed and reinstalled to the microscope.