Development of a Millimeter-Scale Scanning Tunneling Microscope

Abstract

In measuring the roughness of machined surfaces with an scanning tunneling microscope (STM), it is necessary for the STM to have a large scanning area. In this report, a newly developed STM system which meets this requirement is described. It consists mainly of an X-Y stepping motor stage and three tunneling tips along a line, each of which is driven by a piezoactuator. The tip positioned at the midpoint is used as a measuring probe ; the right and the left ones are used as smoothing probes, which are not sensitive to surface roughness and are used to create a kind of reference surfaces. The STM is designed to cancel the relative shift in the z-direction due to thermal drift and/or vibration between the measuring tip and the specimen by means of the two smoothing tips. The basic characteristics of the STM system are investigated and measurements are attempted. The STM makes it possible to perform millimeter-scale scanning without visible reduction in resolution. Moreover, a new system combining an optical sensor with the STM is also constructed. With the use of this system, the results from our STM and those from the optical sensor can be compared closely.