Simplified Besocke scanning tunneling microscope with linear approach geometry

Besocke-style scanning tunneling microscopes are used in low and variable temperature applications because they are compact and the tip-sample spacing is insensitive to thermal drift. It is demonstrated that the economical Besocke design can be simplified even further if a linear approach geometry is used. In this geometry, the sample has only to be moved along two orthogonal axes and just 11 wires are required to control both tip-sample approach and image acquisition. This simplifies the control electronics, increases the reliability of the microscope and, if the microscope is operated in a cryostat, it weakens the thermal link between low and room temperature. Nevertheless, all of the advantages of the Besocke design are retained including thermal compensation of the tip-sample spacing. A self-aligning mechanism is also described that automatically locates the sample relative to the scanner before tip-sample approach. This feature is particularly useful because the microscope is designed for remote operation in a cryostat where there is restricted visual access. Graphite was used as a test surface and images are presented of beta-site corrugation and moire supermeshes. (C) 2004 American Institute of Physics.