Defects and their movement in Pb and Ge nanocrystals characterized by ultra-high vacuum high resolution transmission electron microscope

Defects in Pb and Ge nanocrystals deposited on thinned Si 110.substrates have been studied by a 200-kV ultrahigh vacuum field emission transmission electron microscope UHV-FE-TEM.. The nanocrystals ranged from 2 to 10 nm in size and contained several types of defects that are observable in the w110x direction. High-resolution transmission electron microscopy HRTEM.indicated that the most frequently observed defects in these particles are stacking faults, twins and Frank partial dislocations. The possibility of defect formation in Pb nanocrystals is much higher than that in Ge nanocrystals. Frank partial dislocations are detected both near the surface and at the central part of Ge nanoparticles. The structural fluctuation of Pb nanocrystals has been recorded at a video rate of 1r60 s, showing the movement and annihilation of the defects. In Pb nanocrystals, Frank partial dislocations and twin boundaries TBs.moved within 1 s, while the defects in Ge nanocrystals were stationary. q2000 Elsevier Science B.V. All rights reserved