[Show abstract][Hide abstract] ABSTRACT: The phase transition process of clean (111) silicon surfaces between the (7 × 7) and (1 × 1) structures at about 830°C was directly observed by reflection electron microscopy, which had been briefly reported in a previous short communication (Osakabe et al., Japan. J. Appl. Phys, 19 (1980) L309). Smooth atomic steps, whose shapes change spontaneously and continually in a microscopic scale at high temperature of the (1 × 1) structure, transform into zig-zag steps at low temperature of the (7 × 7) structure, where the changes of the step shape stop. On cooling, domains of the (7 × 7) structure nucleate preferentially on upper terraces along the steps and expand on the terraces to the neighbouring steps. Out of phase boundaries with phase differences of 2πn/7 are seen to be formed. On heating the reversed process takes place. The out of phase boundaries are easy places to transform to the (1 × 1) structure. The observations clearly suggest the phase transition of the first order and the models of the (7 × 7) structure of ordered vacancies or adatoms rather than of static displacements of surface atoms.
No preview · Article · Aug 1981 · Surface Science Letters
[Show abstract][Hide abstract] ABSTRACT: Reflection electron microscopy in ultra high vacuum has been performed during the process of thermal cleaning which converts the dirty (111) silicon surface of the 1 × 1 structure to the clean surface of the 7 × 7 structure, and during the transformations of the 7 × 7 structure to the 5 × 1, √3 × √3 and 6 × 6 structures produced by deposition of gold up to a few monatomic layers. The reflection images showed the microtopographical aspects of the process and of the transformations to be in close correlation with the structural information given by the reflection diffraction patterns observed simultaneously.
[Show abstract][Hide abstract] ABSTRACT: A recently reported surface study by means of ultra-high-vacuum reflection electron microscopy (Osakabe et al.: Surf. Sci. in press) was extended to further details of clean (111) silicon surfaces. A screw dislocation emergent at the surface was clearly identified as the place at which one surface step terminates with a characteristic line contrast. In the transformation between the (7× 7) and (1× 1) surface structures across 830°C, the surface steps act as nucleation sites : on cooling the (7× 7) structure nucleates at the upper edge of the steps and grows along the upper terraces, while on heating the reversed process takes place.
No preview · Article · Jun 1980 · Japanese Journal of Applied Physics
[Show abstract][Hide abstract] ABSTRACT: An anomalous surface superstructure along 〈11̄0〉 of a clean (111)Au surface and two-dimensional nucleus formation of Pd on an atomically flat (111)Ag surface have been observed by an UHV electron microscope.