School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia.
Ultramicroscopy. 2013 Nov;134:18-22. doi: 10.1016/j.ultramic.2013.06.019. Epub 2013 Jul 3.
Thickness fringing was recently observed in helium ion microscopy (HIM) when imaging magnesium oxide cubes using a 40 keV convergent probe in scanning transmission mode. Thickness fringing is also observed in electron microscopy and is due to quantum mechanical, coherent, multiple elastic scattering attenuated by inelastic phonon excitation (thermal scattering). A quantum mechanical model for elastic scattering and phonon excitation correctly models the thickness fringes formed by the helium ions. However, unlike the electron case, the signal in the diffraction plane is due mainly to the channeling of ions which have first undergone inelastic thermal scattering in the first few atomic layers so that the origin of the thickness fringes is not due to coherent interference effects. This quantum mechanical model affords insight into the interaction of a nanoscale, focused coherent ion probe with the specimen and allows us to elucidate precisely what is needed to achieve atomic resolution HIM.
最近在使用 40keV 会聚探针以扫描透射模式对氧化镁立方体进行成像时，在氦离子显微镜（HIM）中观察到厚度条纹。在电子显微镜中也观察到厚度条纹，这是由于量子力学、相干、多弹性散射被非弹性声子激发（热散射）衰减所致。一个用于弹性散射和声子激发的量子力学模型正确地模拟了氦离子形成的厚度条纹。然而，与电子情况不同，衍射平面中的信号主要归因于离子的沟道，这些离子首先在前几个原子层中经历了非弹性热散射，因此厚度条纹的起源不是由于相干干涉效应。该量子力学模型深入了解了纳米级、聚焦相干离子探针与样品的相互作用，并使我们能够精确阐明实现原子分辨率 HIM 所需的条件。
