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Peter Nellist

Professor Peter Nellist
Professor of Materials

Tel: +44 1865 273656 (Room 154.30.05)
Tel: +44 1865 273777 (reception)
Fax: +44 1865 283333

Nellist group website

Summary of Interests

My research centres on the applications and development of high-resolution electron microscope techniques, in particular scanning transmission electron microscopy (STEM), including atomic resolution Z-contrast imaging, electron energy-loss spectroscopy and applications of spherical aberration correctors. Our technique development work includes methods for the three-dimensional imaging and spectroscopy of materials, and methods to allow high resolution imaging and spectroscopy of radiation sensitive materials.  Always we aim to use microscopy data in a quantitative way to make measurements of the atomic and electronic structure of materials.

Research Publications

 

Projects Available

Explaining dislocation motion by the 3D measurement of core structures using electron optical sectioning
Prof P D Nellist

Almost all materials we use in our civilisation are crystals, and the things that make crystals interesting are their defects.  One of the most important crystals defects are dislocations, and they are key to understanding how materials deform plastically.  In some materials, for examples the tungsten used in fusion reactors, certain types of dislocations can behave in unusual ways, for example by having low mobility making the materials much more brittle.  The explanation of this unusual behaviour probably lies in the detailed atomic arrangement at the core of the dislocation, but a full 3D characterisation of such defects has not before been possible.  Here we make use of a novel “optical sectioning” procedure we have developed in our to determine the structure of dislocations at atomic resolution in 3D using electron microscopy.  Using this approach to relate atomic structure to materials properties allows the rational design of alloys to improve the ductility of important structural materials.

This project would suit someone who enjoys challenging experiments but also wants to experience the excitement of seeing atoms in materials  In addition to hands on experiments, the project will involve data processing using scripting in software packages such as Matlab.

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Fast pixelated detectors for STEM: a paradigm shift in atomic imaging
Prof P D Nellist (in collaboration with the University of Glasgow)

The research proposed here aims to develop entirely new ways of imaging in the scanning transmission electron microscope (STEM), and to use these methods to study materials problems.  The overarching aim that forms the basis of the project is to use recently developed fast pixelated detectors to record two-dimensional diffraction patterns as a function of the position of a focused, atomic-scale, electron beam performing a two-dimensional scan.  The resulting four-dimensional data set is the ultimate STEM imaging experiment.  Such a rich dataset contains information about the phase shift that results from transmission through the sample.  Using an approach similar to holography, information about the composition of the sample, the strain in the sample and the three-dimensional ordering in the sample can be measured.  These developments will allow new types of materials to be observed at atomic resolution and new types of measurements about materials to be made.  The project will involve developing skills ranging from fundamental studies of electron scattering processes to statistical methods and parallel computing along with developing the appropriate experiments on the microscope.

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Probing catalyst behavior: from nano-scale characterization to chemical performance
Prof P D Nellist and Dr L Jones

The chemical activity of metallic nanoparticle catalysts begins with their structure at the atomic scale. The aberration corrected scanning transmission electron microscope AC-STEM is ideally equipped to study these samples, probing local structure, strain, and chemistry. The goal of this project is to continue in the development of methods already developed in the group for bridging the current gap between high-precision nano-characterisation and bulk chemical measurements relevant to industry.

The project will involve training and use of the aberration corrected JEOL ARM200CF at the University of Oxford but also in the chemical activity testing of small quantities of industrially produced nanoparticle catalysts. High throughput analysis will be encouraged including automated data handling approaches. There may be the possibility for in-situ experimentation to be performed as well as other complimentary advanced characterization techniques.

The successful candidate will have either a chemistry, physics or materials science background and be comfortable with both practical experimentation and computation analysis methods. Experience with electron microscopy is a bonus but not a requirement.

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Mapping fluorescent markers in biological samples using low-loss electron energy-loss spectroscopy
Prof P D Nellist, Dr Roland Fleck (Kings College London)

Fluorescence microscopy in light microscopy is a very common technique because it allows the molecular composition of biological structures to be identified through the use of fluorescently-labelled probes of high chemical specificity such as antibodies. Observation of sub-wavelength structures with light microscopes is difficult because of the Abbe diffraction limit. Green light at around 500 nm has an Abbe limit of 250 nm larger than many relevant cellular structures. Resolution is further degraded by detector sensitivity (increasing noise at the expense of signal), wide spread use of signal amplification (reducing spatial resolution) to improve detection and scattering of light. Recent developments in spectroscopy in the electron microscopy now allow optical excitations to be observed with nanometre-scale spatial resolution. The aim of this project is to attempt for the first time to apply these electron microscopy methods to fluorescently-labelled biological structures, creating an entirely new method for characterising biological structures.

Also see homepages: Peter Nellist

Also see a full listing of New projects available within the Department of Materials.