SCANNING TUNNELING MICROSCOPE COMBINED WITH SCANNING ELECTRON-MICROSCOPE FOR THE STUDY OF GRAIN-BOUNDARIES

An instrument that incorporates a scanning electron microscope (SEM) and a scanning tunneling microscope (STM) in an ultrahigh vacuum environment was designed to address the specific difficulties of imaging heterogeneous surfaces. A sample may be mounted in the STM for simultaneous STM and SEM imaging, or transferred to a manipulator where other surface analytical tools may be utilized. The STM is based on a viton-stainless-steel stack design and the SEM employs a 5 kV, electrostatic-lens electron gun. The sample mount is fixed, while the tip can be positioned in three orthogonal directions. Macroscopic positioning of the tip is accomplished using two orthogonal linear piezoelectric ''inchworm'' motors and a stepper motor, whereas microscopic positioning is accomplished with a piezoelectric tube scanner