Hage Fredrik S, Nicholls Rebecca J, Yates Jonathan R, McCulloch Dougal G, Lovejoy Tracy C, Dellby Niklas, Krivanek Ondrej L, Refson Keith, Ramasse Quentin M
SuperSTEM Laboratory, SciTech Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD, UK.
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Sci Adv. 2018 Jun 15;4(6):eaar7495. doi: 10.1126/sciadv.aar7495. eCollection 2018 Jun.
Vibrational modes affect fundamental physical properties such as the conduction of sound and heat and can be sensitive to nano- and atomic-scale structure. Probing the momentum transfer dependence of vibrational modes provides a wealth of information about a materials system; however, experimental work has been limited to essentially bulk and averaged surface approaches or to small wave vectors. We demonstrate a combined experimental and theoretical methodology for nanoscale mapping of optical and acoustic phonons across the first Brillouin zone, in the electron microscope, probing a volume ~10 to 10 times smaller than that of comparable bulk and surface techniques. In combination with more conventional electron microscopy techniques, the presented methodology should allow for direct correlation of nanoscale vibrational mode dispersions with atomic-scale structure and chemistry.
振动模式影响诸如声和热传导等基本物理性质，并且可能对纳米和原子尺度结构敏感。探测振动模式的动量转移依赖性可提供有关材料系统的丰富信息；然而，实验工作基本上局限于体材料和平均表面方法或小波矢情况。我们展示了一种结合实验和理论的方法，用于在电子显微镜中对跨越第一布里渊区的光学和声学声子进行纳米尺度映射，探测的体积比类似的体材料和表面技术小约10至10倍。与更传统的电子显微镜技术相结合，所提出的方法应能使纳米尺度振动模式色散与原子尺度结构和化学性质直接关联起来。
