Sojka Falko, Meissner Matthias, Zwick Christian, Forker Roman, Fritz Torsten
Institute of Solid State Physics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
Rev Sci Instrum. 2013 Jan;84(1):015111. doi: 10.1063/1.4774110.
We developed and implemented an algorithm to determine and correct systematic distortions in low-energy electron diffraction (LEED) images. The procedure is in principle independent of the design of the apparatus (spherical or planar phosphorescent screen vs. channeltron detector) and is therefore applicable to all device variants, known as conventional LEED, micro-channel plate LEED, and spot profile analysis LEED. The essential prerequisite is a calibration image of a sample with a well-known structure and a suitably high number of diffraction spots, e.g., a Si(111)-7×7 reconstructed surface. The algorithm provides a formalism which can be used to rectify all further measurements generated with the same device. In detail, one needs to distinguish between radial and asymmetric distortion. Additionally, it is necessary to know the primary energy of the electrons precisely to derive accurate lattice constants. Often, there will be a deviation between the true kinetic energy and the value set in the LEED control. Here, we introduce a method to determine this energy error more accurately than in previous studies. Following the correction of the systematic errors, a relative accuracy of better than 1% can be achieved for the determination of the lattice parameters of unknown samples.
我们开发并实施了一种算法，用于确定和校正低能电子衍射（LEED）图像中的系统畸变。该程序原则上与仪器的设计（球形或平面磷光屏与通道电子倍增器探测器）无关，因此适用于所有设备变体，即传统LEED、微通道板LEED和斑点轮廓分析LEED。基本前提是具有已知结构且有足够数量衍射斑点的样品的校准图像，例如Si(111)-7×7重构表面。该算法提供了一种形式体系，可用于校正同一设备生成的所有后续测量。具体而言，需要区分径向畸变和不对称畸变。此外，为了得出准确的晶格常数，必须精确知道电子的初始能量。通常，真实动能与LEED控制中设置的值之间会存在偏差。在此，我们介绍一种比以往研究更准确地确定此能量误差的方法。校正系统误差后，对于未知样品晶格参数的测定，可实现优于1%的相对精度。
