Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
Phys Rev Lett. 2012 Dec 14;109(24):246101. doi: 10.1103/PhysRevLett.109.246101. Epub 2012 Dec 12.
Aberration-corrected scanning transmission electron microscopy yields probe-position-dependent energy-loss near-edge structure (ELNES) measurements, potentially providing spatial mapping of the underlying electronic states. ELNES calculations, however, typically describe excitations by a plane wave traveling in vacuum, neglecting the interaction of the electron probe with the local electronic environment as it propagates through the specimen. Here, we report a methodology that combines a full electronic-structure calculation with propagation of a focused beam in a thin film. The results demonstrate that only a detailed calculation using this approach can provide quantitative agreement with observed variations in probe-position-dependent ELNES.
像差校正扫描透射电子显微镜提供了与探针位置相关的能量损失近边结构（ELNES）测量，有可能提供潜在的底层电子态的空间映射。然而，ELNES 计算通常描述的是在真空中传播的平面波的激发，忽略了电子探针在穿过样品时与局部电子环境的相互作用。在这里，我们报告了一种将全电子结构计算与薄样品中聚焦束传播相结合的方法。结果表明，只有使用这种方法的详细计算才能与观察到的探针位置相关的 ELNES 变化定量吻合。
