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.
Takeguchi
Masaki
M
Nanomaterials Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan. TAKEGUCHI.Masaki@nims.go.jp
Mitsuishi
Kazutaka
K
Tanaka
Miyoko
M
Furuya
Kazuo
K
D008854:Microscopy, Electron / Q000379:methods*; D010165:Palladium / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
D010165:Palladium; D012825:Silicon