Scattering of the S1 surface state electrons of two-dimensional electron gas (2DEG) by a vacancy complex on a Si(111) √3 x √3–Ag surface was studied. The interference between the incident and scattered electrons caused a standing-wave pattern around the vacancy. The standing-wave pattern was successfully observed in scanning tunnelling microscope based dI/dV images at room temperature. The scattering potential of a vacancy complex with a 1.60nm radius was then evaluated. Because the vacancy was large, S, P and D waves should be considered due to centrifugal potentials with the partial wave theory. So far, the S-wave approximation and its asymptotic form were used without examining the validity. The validity of the S+P+D wave approximation was confirmed, as well as the applicable range of their asymptotic forms to fit experimental data and obtain phase shifts. The scattering potential of the S+P+D wave approximation derived from the phase shifts was 1.70–1.80eV.

Scattering Potential Evaluation with S+P+D Wave Expansion of a Vacancy Complex on a Si(111) √3 x √3–Ag Surface. S.Minamoto, H.Hirayama: Materials Science and Engineering B, 2009, 161[1-3], 16-9