Journal of Electron Microscopy 51:S45-S49 (2002)
© 2002 Oxford University Press
Full-length paper |
Structural observation of Pd silicide islands on Si (111) surfaces with UHV-TEM/STM
Nanomaterials Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan
To whom correspondence should be addressed. E-mail: TANAKA.Miyoko{at}nims.go.jp
Deposition of Pd on clean Si (111) and (110) substrates was performed and observed with a newly developed ultrahigh vacuum-transmission electron microscopy/scanning tunnelling microscopy (UHV-TEM/STM) combined system to clarify the growth process of Pd silicide. Annealing of Pd deposited substrates to 300400°C resulted in the formation of Pd2Si structure. When the Pd coverage was 8 ML, formation of (3 x 3) structure was observed on top of Pd2Si islands with STM. Deposition of Pd on to TEM substrates at 400°C also resulted in the formation of Pd2Si islands. On the surface of the silicide layer, superstructure with three times periodicity was found by profile high-resolution TEM. STM height distribution and electron energy-loss spectroscopy spectrum suggest that this (3 x 3) structure is rather Si-rich and has a subsurface layer. Upon annealing this specimen at 1000°C, (2
3 x 2
3) superstructure was observed with STM.
Keywords scanning tunnelling microscopy, transmission electron microscopy, surface structure, silicon, palladium, silicide