Scattering of the S1-surface state electron by an isolated adatom at Si(1 1 1)√3×√3-Ag surface

We studied the scattering of the S1 surface state electrons of two-dimensional electron gas (2DEG) by an isolated adatom at the Si(1 1 1)√3×√3-Ag surface. The interference between the incident and scattered electrons caused a standing wave pattern around the adatom. It was successfully observed in scanning tunneling microscope (STM) based dI/dV images at room temperature. In the analysis of the standing wave pattern, we numerically confirmed that the S-wave approximation and usage of the asymptotic form of the Bessel function are valid. This enabled us to deduce an analytical equation to fit the experimentally observed standing wave pattern to estimate the scattering potential. The fitting was satisfactory and gave a scattering potential and a surface electron coherent length of ∼6.5eV and ∼15nm at room temperature.