Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany.
Department of Bioengineering, Imperial College London, UK.
J Synchrotron Radiat. 2019 Nov 1;26(Pt 6):1996-2012. doi: 10.1107/S1600577519012773.
An alternative approach to hard-X-ray photoelectron spectroscopy (HAXPES) has been established. The instrumental key feature is an increase of the dimensionality of the recording scheme from 2D to 3D. A high-energy momentum microscope detects electrons with initial kinetic energies up to 8 keV with a k-resolution of 0.025 Å, equivalent to an angular resolution of 0.034°. A special objective lens with k-space acceptance up to 25 Å allows for simultaneous full-field imaging of many Brillouin zones. Combined with time-of-flight (ToF) parallel energy recording this yields maximum parallelization. Thanks to the high brilliance (10 hν s in a spot of <20 µm diameter) of beamline P22 at PETRA III (Hamburg, Germany), the microscope set a benchmark in HAXPES recording speed, i.e. several million counts per second for core-level signals and one million for d-bands of transition metals. The concept of tomographic k-space mapping established using soft X-rays works equally well in the hard X-ray range. Sharp valence band k-patterns of Re, collected at an excitation energy of 6 keV, correspond to direct transitions to the 28th repeated Brillouin zone. Measured total energy resolutions (photon bandwidth plus ToF-resolution) are 62 meV and 180 meV FWHM at 5.977 keV for monochromator crystals Si(333) and Si(311) and 450 meV at 4.0 keV for Si(111). Hard X-ray photoelectron diffraction (hXPD) patterns with rich fine structure are recorded within minutes. The short photoelectron wavelength (10% of the interatomic distance) `amplifies' phase differences, making full-field hXPD a sensitive structural tool.
已建立了一种硬 X 射线光电子能谱（HAXPES）的替代方法。仪器的关键特点是将记录方案的维度从 2D 增加到 3D。高能动量显微镜以 0.025Å 的 k 分辨率检测初始动能高达 8keV 的电子，相当于 0.034°的角分辨率。具有高达 25Å 的 k 空间接受度的特殊物镜允许同时对多个布里渊区进行全场成像。结合飞行时间（ToF）平行能量记录，这可实现最大程度的并行化。由于 PETRA III（德国汉堡）线 P22 的高亮度（<20µm 直径的光斑中为 10hνs），该显微镜在 HAXPES 记录速度方面创下了基准，即每秒对核心层信号进行几百万次计数，每秒对过渡金属的 d 带进行一百万次计数。使用软 X 射线建立的层析 k 空间映射的概念在硬 X 射线范围内同样有效。在 6keV 的激发能量下收集的 Re 的尖锐价带 k 图案对应于直接跃迁到第 28 个重复布里渊区。在 5.977keV 时，Si(333)和 Si(311)单色器晶体的测量总能量分辨率（光子带宽加 ToF 分辨率）为 62meV 和 180meV FWHM，Si(111)为 450meV。在几分钟内记录了具有丰富精细结构的硬 X 射线光电子衍射（hXPD）图案。短的光电子波长（原子间距离的 10%）“放大”了相位差，使全场 hXPD 成为一种敏感的结构工具。
