Where have all the speckles gone? Incoherence and decoherence in fluctuation electron microscopy

Add to your list(s) Download to your calendar using vCal

• Mike Treacy, Department of Physics, Arizona State University
• Thursday 19 January 2017, 16:00-17:00
• Mott Seminar Room, Cavendish Laboratory.

If you have a question about this talk, please contact Stephen Walley.

Fluctuation electron microscopy (FEM) examines the statistics of speckle arising in dark-field scattering from disordered materials. The role of illumination spatial incoherence in coherent speckle is well understood. What was baffling, however, was the persistence of an anomalously high incoherence even when the illumination was highly coherent. The effect is not subtle: speckle intensities can be suppressed by up to two orders of magnitude. The likely culprit is displacement decoherence, which is a type of enhanced Debye-Waller effect originating from quasi-elastic and inelastic momentum exchanges between the beam and the material. Beam damage, and associated long-range strain fields contribute mainly to the effect. Atoms under a high energy electron beam move much more than is generally acknowledged: popcorn under a blowtorch provides a dramatic analogy.

This talk will explain the basics of FEM , and how it is used to probe amorphous materials. The role of incoherence, and its role as an adjustable parameter, will be explained. The physics of speckle, and our inference of displacement decoherence, will be outlined.

This talk is part of the Physics and Chemistry of Solids Group series.

This talk is included in these lists:

• All Cavendish Laboratory Seminars
• All Talks (aka the CURE list)
• Art Cell Gallery Exhibtions
• Cambridge Advanced Imaging Seminars
• Centre for Health Leadership and Enterprise
• Electron Microscopy Group Seminars
• Featured lists
• ME Seminar
• Mott Seminar Room, Cavendish Laboratory
• Museums in Cambridge
• Neurons, Fake News, DNA and your iPhone: The Mathematics of Information
• Physics and Chemistry of Solids Group
• School of Physical Sciences
• Thin Film Magnetic Talks
• cambridge advanced imaging

Note that ex-directory lists are not shown.