Ultra-high vacuum electron microscope study on Micro-processes of surface and crystal growth.

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A new high resolution UHV (ultra-high vacuum ) electron microscope has been developed for in-situ surface study at atomic level resolution. The microscope has the vacuum of <10^(-8)> level after baking at 100 ゜ C and the resolution of 0.22 nm. With deposition facilities, metals and semiconductor materials were deposited on substrate surfaces places at the specimen position in-situ in the microscope. Surface processes, then, are imaged in transmission and reflection electron microscopy and diffraction.We performed in-situ surface studies for Si(111)7x7 reconstruction and the phase transition, for metal adsorption on Si surface and for metal cluster. By transmission electron diffraction, the reconstructed Si(111)7x7 surface was found to have dimer adatom stacking-fault (DAS) structure. Adsorption processes of Ag, Au, Cu and Al on the 7x7 surface were observed by reflection electron microscopy. Surface steps were found to work as the nucleation site. Phase transition of Si(111)7x7 process was observed by high resolution reflection microscopy, 2.3 nm spaced superlattice fringes being resolved. The phase boundary between the 7x7 and "1x1" structure was found to be vary narrow throughout the transition process. In addition to these studies, structures and dynamical behavior of clusters consisting a few to several tens of Au atoms were seen at atomic level.The high resolution UHV electron microscopy, thus, is useful for basic and applied surface science.