SURFACE OBSERVATION OF MO NANOCRYSTALS DEPOSITED ON SI(111) THIN-FILMS BY A NEWLY DEVELOPED ULTRAHIGH-VACUUM FIELD-EMISSION TRANSMISSION ELECTRON-MICROSCOPE

An ultrahigh vacuum field-emission transmission electron microscope (U HV-FE-TEM) has been newly developed for the observation of semiconduct or surfaces. It provides ultrahigh vacuum environment of 2.0 x 10(-8) Pa for surface studies, in addition to high contrast electron probe wi th large beam current for high-resolution transmission electron micros copy (HRTEM). Nanometric surface analysis using energy dispersive X-ra y spectroscopy (EDS) and electron energy loss spectroscopy (EELS) can be carried out simultaneously with HRTEM. Deposition of Mo onto both a s-prepared and cleaned Si (111) TEM samples was performed at room temp erature. HRTEM and EDS analysis suggest the formation of Mo nanocrysta ls. The size of the nanocrystals was about 2-3 nm on as-prepared sampl e, and 10-15 nm on cleaned sample. Electron beam irradiation resulted in the formation of Mo-related compound in as-prepared sample case, an d sputtering or sublimation of Mo and Si in cleaned sample case. (C) 1 998 Published by Elsevier Science S.A.