In situ UHV-TEM observation of the direct formation of Pd2Si islands on Si(111) surfaces at high temperature

Pd was deposited on clean Si surfaces at about 680 K in an ultrahigh-vacuum transmission electron microscope. The direct formation process of Pd,Si is lands on Si(lll) surfaces was observed in situ by high-resolution transmiss ion electron microscopy in a cross-sectional view, At a low deposition amou nt, Si(111) 7 x 7 surfaces were transformed to a new layer due to the cover age by Pd. With further deposition, Pd,Si islands appeared on Si surfaces. Some Pd,Si islands were single crystals and grew epitaxially on Si(lll) sur faces in the Stranski-Krastanow mode. After stopping Pd deposition, the sur face of the Pd,Si islands exhibited a reconstruction structure with threefo ld periodicity, which consists of two atomic layers. (C) 2000 Elsevier Scie nce B.V. All rights reserved.