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Graduate Opportunities

Graduate Research Projects in the SMF Group (PhD and MPhil Degrees)

Understanding the dynamical properties of materials, from individual atoms and molecules on surfaces, to the effect of defects and bulk structure remain substantial physical challenges.  In the SMF group, we aim to investigate the physics of such processes at the most fundamental level practical.

Across the group, we apply an exceptionally wide range of experimental techniques, from nano-scale imaging to macroscopic materials tests, and we have a strong emphasis on development of innovative experimental techniques.  Our projects are primarily experimental, but the group also pursues a considerable computational modelling effort - ideal for those people wishing to focus on modelling or theory, while maintaining a grounding in experiment.

 

Application and Funding

Information about the application procedure is available on the departmental website.  All projects are available to students applying for Departmental Quota Award studentships or other personal awards.  In addition, there are a number of other studentships available for work in specific areas, and many projects have dedicated funding streams.

 

PhD Projects for 2019 Entry

Development of nano-scale Chemical Contrast in Atom Scattering (Dr Nadav Avidor) (†)

Chemical contrast makes photon and electron based probes applicable to questions in surface-chemistry. While atom scattering, and in-particular helium scattering, offers some great advantages over traditional techniques (including supreme surface-sensitivity), it remains inapplicable to many problems in surface chemistry due to the notion that atom scattering lacks chemical contrast. Combining technological developments with advanced interpretation of inelastic and quasi-elastic helium scattering (time-of-flight and spin-echo) measurements, the project aims to develop the mechanisms to obtain chemical contrast in helium scattering. Further, we will apply the technique to study surface reactions, including dissociation of CO2 and methanol, and the conversion of CO2 (greenhouse gas) to methanol (alternative fuel).

The project is multi-disciplinary in nature, with potential for both MPhil and PhD opportunities in experimental work on ultra-fast surface dynamics and surface-reactions, instrument development, and software development (including advanced simulators for diffusion and scattering). In addition, work on neutron scattering experiments is a possibility, to propagate our advancement to that field. The project inherently involves taking active part in international collaborations.

 

Experimental and Theoretical Investigations of Rate Theory Using He Spin-Echo (Dr John Ellis)

Why and how fast do things change? This is one of the basic questions in fundamental science – underlying everything from the dephasing of qubits and tunnelling diffusion of hydrogen, to the self-assembly processes which underpin biology and upon which so much hope is pinned in the realm of nanotechnology. The foundations of ‘rate theory’ were laid in the 1930s with the development of transition state theory (TST) – a classically conceived approach which involves a host of assumptions. Whilst TST is useful for ‘back of the envelope’ calculations of the rate of change of systems connected to a heat bath (which accounts for the overwhelming majority of processes), it is not quantitatively accurate.  Methods for quite accurately calculating atom interaction energies are now available (although they are immensely computationally demanding), but TST is still very widely used to bridge the gap between system energetics and the rate of a process – effectively squandering the energy accuracy that has previously been achieved. The situation could continue because of the lack of actual measurements of rate processes on atomic length and time scales have limited development of theory.  Specifically, the key prefactors derived in most experiments are so inaccurate that they are useless for probing rate theory. Fortunately, with the advent of Helium spin-echo measurements, it has become possible to measure the motion of atoms at surfaces on the necessary picosecond time and nanometre length scales very accurately, enabling both classical and quantum rate approaches to be studied. In this project it is proposed to undertake a series of measurements targeted at answering the many key questions that are still open.  The aim to develop a coherent picture of how you actually ‘do’ rate theory in real situations – from both classical and quantum perspectives.

 

Fundamental Lithium-Carbon Interactions (Dr Andrew Jardine) (†)

The need to move towards green electricity means the importance of battery technology is continually increasing – and Lithium Ion batteries are one of the most common.  Carbon electrodes are widely used, and there is much active research into the use of novel forms of carbon to improve battery performance. However, our understanding of the atomic-scale interactions, und the fundamental physics that underpins them, is limited.  The aim of this project is to characterise the interactions that underpin nanoscale mobility in model lithium-carbon systems (including graphite and/or graphene substrates).  Specifically, we aim to understand the mechanisms of motion, interaction potentials, rate limiting transport barriers, and energy exchange rates – all of which are directly relevant to technological application. The project will be based around experimental spin-echo measurements supported by a range of other complimentary techniuqes.

 

Microscopic Imaging with Twisted Atoms (Dr Andrew Jardine)

We have recently developed a new form of microscopy that uses thermal energy neutral helium atoms as the surface probe (SHeM).  The method is ultra-sensitive, and will enable many previously inaccessible surfaces to be studied, ranging from light sensitive molecules, to delicate polymers making up MEMS structures.  The aim of this research project is to further extend the technique, by developing Fresnel zone plate based focal elements that have optimised apertures designed to generate atom microprobes with angular momentum. Such beams have potential to generate unique forms of contrast from, for example, chiral surfaces. The project will involve both design and microfabrication techniques, as well as integrating the devices with the helium microscopes currently being developed in the laboratory as part of a £1M grant programme.  The project will benefit from ongoing collaborations with European and Australian physicists in this area.

 

Hydrogen mobility on surfaces (Dr John Ellis)

Understanding hydrogen mobility is vitally important to the modern world, from fuel cells, to energy storage, to the embrittlement of metals.   However, the fundamental processes controlling its motion between atoms is still not well understood – even the relationship between classical hopping and quantum tunnelling between different surface sites cannot easily be predicted.  The aim of this project will be to experimentally study the transition from classical to quantum H motion on metal surfaces, using helium spin-echo spectroscopy (HeSE).  The method represents a unique experimental approach pioneered in Cambridge, which provides unprecedented data quality and precision.  There will be opportunities to link the project with theory, to model the experimental data, depending on individual interests.  Some collaboration with national and international collaborators (both experimentalists and theorists) is very likely.

 

Morphology and Growth of Ice (Dr Andrew Jardine)

Ice is a vitally important material, yet is still not well understood.  A range of unusual and complex morphologies are formed during low-pressure growth, ranging from regular arrangements to complex ‘worm-like’ structures.  However, it is almost impossible to study these structures at high resolution – electron microscopy causes melting, and scanning probe techniques cannot cope with the high aspect ratio structures that are formed. The aim of this project is therefore to study the growth / structures formed by ice using helium microprobes – one of the few suitable tools.  The project will involve both helium scattering and helium microscopy, using existing equipment developed in the group.  The project is primarily experimental, but could be extended to include simulation/modelling.  It will involve working closely with international collaborators.

 

Dynamic processes in organic film assembly (Dr John Ellis) (†)

Organic films are of wide-ranging importance; for example in organic electronics as a technology for low cost devices, or in large scale solar cells.  The performance of such devices is controlled by the quality of preparation of molecular thin films and heterostructures.  Since top-down structuring methods like lithography cannot be applied to van der Waals bound materials, surface diffusion becomes a structure determining factor that requires microscopic understanding.  The aim of this project will be to study the dynamics of species relevant to the organic electronics industry, including pentacene and fluorinated variants thereof, which enable the level of conjugation to be tuned.  The project will include organic monolayer optimisation, dynamics data collection, and analysis.  There will be opportunity to combine experiments with extensive molecular dynamics simulations, to further interpret the experiments, depending on individual interests.  The project will involve collaboration with researchers in Germany.

 

Nanoscale control of single crystal diamond mechanics (Dr AP Jardine) (†)

Diamond is an immensely important material both from a fundamental perspective, and in applications as diverse as quantum-computer development and highly optimised mechanical tooling.  Many diamond properties are closely related to the defect structure within the material (e.g. carbon vacancies, impurities).  Mechanically, the strength and toughness of diamond are both closely linked to the atomic scale defect-structure, but are vital to optimising its use in tooling.

Techniques are available to modify diamond on the nanoscale, and the overall aim of this project is to improve our understanding of the relationship between nanostructure and macroscopic mechanical properties.  It will involve characterisation of nanoscale properties, performing experiments to study macroscopic mechanical characteristics and running computer simulations to examine the structure of defects, and to bridge the gap between nano- and macro- regimes.  The project will form a collaboration with a major industrial partner, and the candidate will benefit from the opportunity to work directly with them for a period of time.

 

Effect of structure on dynamics of geological materials (Dr C Braithwaite)

The dynamic mechanical response of geological materials is of great importance, both industrially and scientifically, with applications ranging from seismology and planetary impact, to oil exploration and mining. The materials themselves are often complex and polycrystalline with a variety of constituent minerals and wide range of inherent length scales. While significant research has been conducted in the field, currently there is a lack of data examining the effect that the microstructure plays in determining strength parameters.  This project aims to use a variety of existing high strain rate experimental equipment to examine the response of geological materials. Novel methodologies and diagnostics will need to be developed to monitor grain level behaviour and relate this to macroscale properties. Interaction with computational modelling will also be sought, to enhance the understanding of the experimental results obtained. The research group has substantial experience in this area and maintains a variety of relevant industrial contacts.

 

Granular materials under high rates of compaction (Dr CH Braithwaite)

The processes by which brittle granular materials compact largely depend on their microstructure and the properties and interactions of the grains themselves. Predicting the dynamic response of these systems requires knowledge of how grain-scale phenomena manifest as macroscopic response. Such insight is crucial for a wide range of high rate applications including planetary formation and impact cratering, the response to blast and

penetration, and predicting and improving soil response to earthquakes and landslips through seismic coupling.  This project will follow on from a highly successful project studying the shock compaction of cohesionless sands at different moisture levels; it will extend the research programme to silts (smaller grain sizes), cohesive materials such as clays, and will begin to study how granular compaction can be controlled using suitable ‘modifiers’.

 

Ultra-fast temperature sensors for shock (Dr DM Williamson)

Accurate temperature measurement during high speed events remains a consistent problem in shock-physics. Existing transducers are rate limited by their thermal mass, whereas standard optical techniques can only be applied under limited conditions (usually very high temperatures). In this project, we will focus on developing new techniques for ultra-fast temperature measurement. These will include modelling, fabrication and testing of nanometre-scale thermistor based instrumentation and fast response infra-red pyrometry. The techniques will be applied to study shock temperatures in polymeric and liquid systems, which are of increasing industrial importance.

 

Adhesion and damage in composites (Dr DM Williamson)

Composite materials are of great importance in the everyday world.  Their fundamentally inhomogeneous nature means composites can exhibit complex forms of behaviour, relating to characteristics of the binder, filler and the nature of the interaction between them.  This project will focus on predicting the behaviour of composites using physically based models, supplemented by experimental data.  Low temperature thermo-physical measurements enable key model parameters to be populated.  Predictions may then be validated using other, mechanically based, measurements.  It will suit a keen experimentalist, and will likely involve extensive collaboration with other researchers.

 

Notes:

(†) – Project to be funded through EPSRC award scheme, or other awards.

(*) – Project to be funded directly, through dedicated project based funding.