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

An instrument that incorporates a scanning electron microscope (SEM) a nd a scanning tunneling microscope (STM) in an ultrahigh vacuum enviro nment was designed to address the specific difficulties of imaging het erogeneous surfaces. A sample may be mounted in the STM for simultaneo us STM and SEM imaging, or transferred to a manipulator where other su rface analytical tools may be utilized. The STM is based on a viton-st ainless-steel stack design and the SEM employs a 5 kV, electrostatic-l ens electron gun. The sample mount is fixed, while the tip can be posi tioned in three orthogonal directions. Macroscopic positioning of the tip is accomplished using two orthogonal linear piezoelectric ''inchwo rm'' motors and a stepper motor, whereas microscopic positioning is ac complished with a piezoelectric tube scanner