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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

Exploring metal plasticity through atomic imaging of core structure
Prof P D Nellist, Prof D E J Armstrong

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, 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 laboratory 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.

Also see homepages: David Armstrong Peter Nellist

Quantum crystallography using electron ptychography
Prof P D Nellist, Dr R J Nicholls, Prof J R Yates

Electron ptychography is a newly available mode of imaging in the transmission electron microscope that is somewhat related to holography and can provide very precise measurements of the electrostatic potential in a crystal.  Recent work in Oxford has shown that it can provide a measurement of the charge transfer between boron and nitrogen in a hexagonal boron nitride monolayer. This work demonstrates the potential of ptychography for measuring the effect of bonding on wavefunctions and charge densities in crystals – a field now known as quantum crystallography.  The aim of this work is to develop this method to measure the effects of bonding in a range of different materials, such as compound nanomaterials and transition metal oxides.  It will involve developing the experimental and data processing approaches, and developing methods based on density functional theory modelling to interpret the experimental data.  Projects are available that have either a more experimental emphasis applying the method to a range of materials, or a greater emphasis on developing the theoretical modelling methods to improve how the experimental results can be interpreted.

Also see homepages: Peter Nellist Rebecca Nicholls Jonathan Yates

Electron ptychographic imaging of polymer and macromolecular ordering
Prof P D Nellist, Prof H E Assender

Electron ptychography is a newly available mode of imaging in the transmission electron microscope that is somewhat related to holography. Recent work in Oxford has shown that it can provide sensitive imaging of low atomic number elements while minimising the number of illumination electrons required. A major challenge associated with electron microscopy of polymers is the damage caused to the sample by the electron beam. The development of electron ptychography creates an opportunity to overcome this challenge and to create a new method for high-resolution imaging of polymers. The project will focus on applying electron ptychography to study local molecular ordering processes in polymer thin films that cannot be studied using conventional X-ray and neutron diffraction methods. The polymer interaction with the substrate will form an important part of the study. The project would suit someone interested in applying state-of-the-art electron microscopy methods to materials that have not traditionally been widely studied using electron microscopy.

Also see homepages: Peter Nellist

Atomic-scale characterisation of Li battery materials
Prof P D Nellist, Prof P G Bruce

Transmission electron microscopy (TEM) is now capable of imaging individual atoms in materials, and electron spectroscopy data can provide atomic-scale information about the elements present and the nature of the bonding. Oxford Materials is one of the leading departments in high-precision quantitative measurements of materials using these methods. These methods have great potential for measuring structure and local chemistry to explain the performance of Li battery materials and to guide their development. The big challenge, however, is that the materials used are very sensitive to damage due to the illuminating electron beam. The aim of this project is to make use of methods recently developed in Oxford to maximise the amount of information gained from the microscope for the minimum electron irradiation. In particular, the recently developed method of electron ptychography (somewhat related to holography) can provide very sensitive measurements of Li and O atoms with three-dimensional information available. This will allow, for example, the positions of Li and O atoms in an electrode to be determined at various stages of the charge and discharge cycle of a battery. The project is suitable for someone interested in applying state-of-the-art atomic resolution electron microscopy to an important and rapidly developing class of materials.

Also see homepages: Peter Nellist

Exploring the frontiers of electron ptychography
Prof P D Nellist, Prof A I Kirkland

Electron ptychography is emerging as an important new imaging tool allowing greater image contrast of light elements, lower doses for radiation sensitive materials, the ability to correct for imperfections in the optics and the retrieval of 3D information. The technique is already being used for a range of materials applications (see other projects) and is likely to be revolution in the way we perform atomic resolution characterisation of materials. The aims of this project are to explore how far the technique can be pushed and how new measurements of materials can be made. Broadly, ptychography can be performed in two different configurations. The sample can be illuminated by a converged beam which is then scanned over the sample. Fast cameras are used to record diffraction patterns for each illuminating position, to form a 4D data set. Alternatively, a parallel illuminating beam can be tilted and a series of images recorded in a conventional TEM. Both modes will be developed as part of exploring the optimal conditions. Leading electron microscopes in the Department of Materials and at the Diamond Light Source at Harwell will be used.

Also see homepages: Peter Nellist

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