We investigated Indium (In) atomic wires on the stepped Si surface by scanning tunneling microscopy (STM) and examined the (112) step model within the reconstructed Si(557) surface using a planewave pseudopotential calculation based on the density functional theory (DFT). The stepped surfaces have attracted much attention because a stepped structure itself can be a useful template for the growth of atomic/nano wires. One of the noticeable stepped surface is the Si(557) surface. The reconstructed Si(557) surface was proposed to a good template with a single periodicity of 5.7nm [APL, 79, 1608]. This reconstructed surface structure is composed of a half-unit cell of the Si(111)7×7 surface and a triple bunched step, approximated by a Si(112) facet, which are arranged alternatively. However, the step structure is not clearly resolved until now. So, we try to suggest a possible step model and use this surface as a template for making 1D structure.
For the clean Si(112) surface, we examined our stable model: adatom-dimer model. Based on this model, the simulated STM image of a Si(112) step within the reconstructed Si(557) is good agreement with experimental STM images. Calculated the probability densities of electron (PDE) and density of states (DOS) of clean (112) steps are shown some possible states below the Fermi level within in 1eV for the potential reaction sites.
The In atomic wires were grown on the reconstructed Si(557) surface at room temperature(RT). They are found to form between the Si(111)7×7 units, i.e. on the triple bunched steps, at low coverage. The In atomic wires with a width of 1 nm are arranged very uniformly parallel to the step, located at the second step of a triple step. The periodicity of atomic wires is exactly the same as that of surface with about 5.7nm. At higher In coverage, another atomic wire is noticed to grow proximate to the atomic wire grown at lower In coverage. We could show a possibility to grow the uniform atomic wires with a width down to an atomic scale by adsorbing Indium on the stepped surface at RT and to control the number of wires on the surface by In coverage. |