The Design of an Ultra-High Vacuum Specimen Environment for High Resolution Transmission Electron Microscopy.

A JEOL 200CX High Resolution Transmission Electron Microscope with point-to-point resolution 2.5angstroms has been modified to achieve an ultra-high vacuum specimen environment (~ 10 sup -9 tau). In-situ heating and evaporation are provided in the specimen viewing position, where high resolution can be maintained at temperatures exceeding 600C. Our design employs complete differential pumping of the specimen chamber and the use of a He-cooled cryo-shield at the specimen for best vacuum attainment. Our design philosophy permits the instrument to be used for a wide variety of in-situ experiments, including low-pressure ( 10 sup -1 tau) gas reaction.