Direct UHV-TEM observation of palladium clusters on a silicon surface.
About 1 monolayer of palladium was deposited onto a silicon (111) 7 x 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 x 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 x 1 surface layer were directly observed by in situ plan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 x 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 x 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 x 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described.
Nanomaterials Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan. TAKEGUCHI.Masaki@nims.go.jp
Masaki
M
Takeguchi
Kazutaka
K
Mitsuishi
Miyoko
M
Tanaka
Kazuo
K
Furuya
D008854:Microscopy, Electron / Q000379:methods*; D010165:Palladium / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
D010165:Palladium; D012825:Silicon