Study of elastic and inelastic scattering electrons in diffraction pattern by energy filtered RHEED observation

通过能量过滤的RHEED方法，明确了构成RHEED图形的弹性和非弹性散射电子的以下几个方面。1.去掉传统RHEED图案中的非弹性散射分量，由于背景强度降低和菊池谱线消失，衍射图案的对比度变高。(1)对于Si(001)2xl表面，从背景中清晰地提取出由c(4x2)结构无序产生的孤立图案。(2)对于邻近的Si(111)7×7表面，在零损耗RHEED花样中，在穿过镜面光斑的垂直线上发现了一些额外的光斑。结果表明，这些额外的光斑可以用规则的台阶面来解释。(3)对于Al在Si(111)上的伽马相结构，从零损耗谱出发，表面结构被运动学分析为9×9非公度结构。2.为了研究非弹性散射电子的能量损失，能量LOS…对几束衍射束、菊内线和本底进行了更多的S光谱测量。结果表明，RHEED光束受表面等离子体损耗的影响很大，表面等离子体损耗的大小与入射光束的掠射角和衍射光的起始角有关。3.研究发现，常规摇摆曲线与零损耗摇摆曲线的相对强度不同。随着非弹性成分的去除，低角侧峰的相对强度减小。这意味着更多的掠入电子束遭受表面等离子体损失的可能性更大。提出了在摇摆曲线的动力学计算中，通过引入向真空扩散的虚势，可以唯象地处理这种峰强度降低的问题。4.在以非弹性散射强度为中心的RHEED振荡机制研究中，考察了Al在Si(111)7x7和Si(111)3x3-Al两种不同衬底上的室温生长模式的差异。结果表明，铝在7×7表面上呈岛状生长模式，而在3×3-Al表面上为层状生长模式，但并不理想。较少

The following aspects concerning elastic and inelastic scattering electrons constructing a RHEED pattern were made clear by energy filtered RHEED method. 1. Removing the inelastic scattering components from a conventional RHEED pattern, the contrast of the diffraction pattern becomes higher as a result of decreased background intensity and disappearance of Kikuchi lines. (1) For Si (001) 2xl surface, a lone pattern, which is produced by a disordering of the c(4x2) structure, was extracted clearly from the background. (2) For a vicinal Si (111) 7x7 surface, some extra spots in the vertical line across the specular spot were found in the zero-loss RHEED pattern. It was demonstrated that these extra spots can be explained by a regular step surface. (3) For the gamma phase structure of Al on Si (111), the surface structure was kinematically analyzed as 9x9 incommensurate one from the zero-loss pattern. 2. In order to investigate the loss energy of inelastic scattering electrons, energy los … More s spectroscopies were measured for several diffraction beams, Kikuchi line and background. It was found that RHEED beams suffer surface plasmon loss strongly and the magnitude of surface plasmon loss depends on both the glancing angle of incident beam and the take-off angle of the diffraction beam. 3. It was found that a conventional rocking curve differs from the zero-loss one in the relative intensity. The relative intensity of a peak at lower angle side decreases as removing the inelastic components. This means that more grazing electron beam suffers surface plasmon loss with higher probability. It was proposed that such decreased peak intensity can be phenomenologically treated in the dynamical calculation of the rocking curve by introducing an spread imaginary potential toward vacuum. 4. In the beginning of the study on RHEED oscillation mechanism focused on inelastic scattering intensity, the difference of Al growth mode at room temperature on the two different substrates, Si (111) 7x7 and Si (111) 3x 3-Al surfaces, was examined. It was found that Al deposition on 7x7 surface reveals island growth mode, however, that on 3x 3-Al surface layr by layr growth mode but imperfect. Less