DEVELOPMENT AND APPLICATIONS OF A 300-KEV ULTRAHIGH-VACUUM HIGH-RESOLUTION ELECTRON-MICROSCOPE

A commercial 300 keV high-resolution electron microscope has been modified for ultrahigh-vacuum operation by the provision of a novel specimen chamber, additional treatment- and cryochambers and extra pumping capacity. Measured vacuum levels after bakeout cycles are in the mid to low 10(-9)) Torr range. The side-entry-type specimen holder incorporates a flexible bellows connection to minimize vibrations and thermal drift problems. The interpretable resolution of the microscope of 0.20 nm has been retained after completion of the UHV conversion, and the microscope has subsequently been used in the profile imaging and reflection microscopy geometries to study a variety of semiconductor, oxide and metal surfaces and surface reactions. These include the 7x7 Si{111} and 1x1 GaP(110) surface reconstructions, and phase transitions between 2x1 and 3x1 reconstructions of the CdTe(100) surface. The effects of electron irradiation, and also annealing, on MgO and rutile surfaces have been documented.