|
Low dimensional structures generated by metal adsorption on semiconductor surfaces exhibit a variety of exotic physical phenomena and have the potential as the cornerstone for nano-scale device. Especially, Au/Si(111) systems have become fascinating due to the ease to fabricate one dimensional structures with tailored electronic properties.
Among of Au/Si(111) system, Si(111)-5×2-Au is a self-organized, one-dimensional system with the two rows of dimerized substitutional Au chains along [110]. Unique to this surface are randomly distributed short chains of Si adatoms called bright protrusions (BP's), rendering the local periodicity to 5×4, and described as a lattice fluid. The previous works by STM experiment and first principle calculation show that the BP's act as electron donors, doping the parent 5×2 band structure to reduce its surface energy. Recently, it was known that the density of BP's can be controlled by additional Si evaporation (high) or rapid thermal annealing (low).
In our work, we directly observed the peculiar inhomogeneity on the Si(111)-5×2-Au using the rapid thermal annealing method by scanning tunneling microscopy (STM). STM reveals that the inhomogeneity occurs at finite atomic length pinned by BP's and exhibits dynamic behavior, which is fluctuating at room temperature. Furthermore, the inhomogeneity only happens on the odd length more than 9a0 where a0 is the lattice constant of the (111) plane. Upon cooling, the dynamic behavior of inhomogeneity is frozen and the frozen feature obviously shows that there is the existence of domain wall in the odd length. Therefore, the dynamic inhomogeneity on Si(111)-5×2-Au with lacking dopants (BP's) at RT can be interpreted in terms of moving domain boundary, so called "soliton". |