Extremely High Vacuum System for Dynamical Surface Analysis

In order to investigate surface structures dynamically, it is necessary to reduce the influence of adsorbates on the surface. We have developed an extremely high vacuum (XHV) system that maintains the required pressure even during dynamical reflection high energy electron diffraction (RHEED) observations. The main analysis chamber was evacuated by a Ti sublimation pump and a 4.2 K class cryosorption pump, and the XHV condition (< 1X 10~¹² Torr) could be kept for longer than 200 h without any additional operations. To reduce the outgassing from the components of the pump such as the casing wall and cryopanels, the cryosorption pump was modified to allow baking. Addition of a RHEED system has been done successfully without degrading the XHV condition by using a differential pumping system for a hot cathode electron gun. The total pressure has been kept below 4X10“¹² Torr even when specimens were heated to 1000 K. By using this analysis system, we can observe solid surfaces dynamically by electron diffraction.