Abstract
We have controlled the surface structures of selenium (Se) treated GaAs(001) using a Se molecular beam in a molecular-beam epitaxy (MBE) system and obtained a variety of surface reconstructions. The detailed surface structures were observed in-situ using a high-performance scanning tunneling microscope (STM) system. After producing Ga-stabilized GaAs(001) (4 × 6) reconstructions by thermal cleaning, Se was evaporated slowly onto the surfaces. As the Se deposition time was increased, the surface structure could be changed from (4 × 6) to (4 × 3) to (2 × 3) and finally to the (2 × 1) reconstruction. All surfaces were well ordered and STM images were obtained successfully for all of these reconstructions. The (4 × 3) structure was observed to be similar to (2 × 3), however, dimers might be buckled in alternate directions together with the nearest neighbors in the [1 1 0] direction. The (2 × 3) structure consisted of elliptical protrusions in the dimer rows forming an additional periodicity along the dimer row direction. For the (2 × 1) surface, simple dimers row structures were observed. These structural changes were thought to be caused by irregularities in the SeSe or SeGa dimers and Ga vacancies under the surface. We found that Se coverage played an important role as well as heat treatment in this phase change.
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