If you are a student looking for a PhD project, please see below for a description of my available positions. If you are interested and would like more details please contact me and I'd be happy to discuss.

For Post-Docs, I'm afraid I don't have funding available at present, however if you are competitive to apply for some of the individual post-doctoral fellowships available (for instance see here, and here) and are looking for a host, please contact me with a CV plus small statement of your interests and we can discuss what would make a good proposal to develop and submit.

PHD PROJECTS

Understanding 2D material memristors by atomic resolution imaging

 

FULLY FUNDED EPSRC STUDENTSHIP - see here for details 

The relentless advance of Moore's Law, and the evermore powerful computational capabilities it has gifted us through continued device miniaturisation, will soon cease. We cannot shrink our current silicon-based electronics much further. Designing new devices beyond the traditional MOSFET, realising the potential of new materials, and even developing entirely new computational architectures, will all be necessary to ensure continued progress in computing power.

Resistive memory (ReRAM or memristor), a memory where the on and off states correspond to different resistance states toggled by an applied potential, are an emerging device of intererst in 'beyond Moore' electronics, with potential applications in high-speed memory and neuromorphic 'brain-like' computing. New 2D materials, like monolayer MoS2, can now be used to make these devices atomically thin. However, there remains significant ambiguity over the atomic mechanisms behind this resistive switching property. Understanding this process at the fundamental atomic level would allow us to engineer better devices.

This PhD project will use the state-of-the-art atomic resolution imaging facilities available at Warwick University to diagnose these underpinning mechanisms and thus inform the design of next-generation electronic devices. (See the below figure for an example experimental image). The student will conduct transmission electron microscopy (TEM) imaging of 2D material ReRAM devices while they are being operated inside the microscope. These operando experiments will directly reveal the atomic mechanisms that occur inside an operational memristor. The student will benefit from training in 2D material preparation and handling, semiconductor device fabrication, and TEM imaging techniques, as well as international collaboration with partners in Korea.

LEFT: An atomic resolution TEM image of a MoS2 monolayer, viewed from the top. The bright dots correspond to Mo, and the fainter dots to the S atoms. Running left-to-right through the centre of the image is a line defect, which are predicted to act as conducting channels. RIGHT: The computationally calculated (DFT) atomic model of the TEM image.

Ferroelectricity in 2D materials and their polarisation switching behaviour

A fundamental limitation with current computing architecture is the von-Neumann bottleneck; the delay in feeding data between the processing unit and the memory. Higher speed memory would help alleviate this problem, however, our memory technology currently presents us with a difficult choice: We can either have high-speed memory, but that ‘forgets’ when unpowered (volatile RAM and caches), or we can have memory that ‘remembers’ even when shutdown (non-volatile solid-state drives), but is slow. We currently cannot have both non-volatile and high-speed memory.


Ferroelectric memory (FeRAM) based on certain 2D materials (2DMs) may present an answer to this problem, able to retain their state even when depowered and still operate at high speeds. The observation of ferroelectric polarisation switching in certain 2D materials remains novel and underexplored. Compared to their 3D bulk counterparts, we expect 2D ferroelectrics to behave quite differently due to their spatial confinement. Understanding the atomic structural changes and relationships that facilitate polarisation switching will let us better tailor these materials to future devices.


The PhD student will work on the fabrication of ferroelectric 2DM devices, and characterise them electrically and by operando TEM imaging. The University of Warwick has recently secured a large research grant for new equipment that will allow us to directly image the polarisation state in a material down to the nanoscale. The student will use this to identify polarisation switching in their devices, and correlate it with atomic scale features such as dislocations and grain boundaries. The student will have the opportunity to learn skills in both electronic devices and advanced TEM, and will interact with the Department’s leading ferroelectric and 2D material communities.

Formation of charge density waves in 2D materials

The emergence of charge density waves (CDWs), a periodic distribution of charge density coupled with a symmetry-breaking distortion in the atomic lattice, in certain metal dichalcogenide 2D materials has generated renewed interest in this confined-dimensionality phenomenon. Despite having been investigated for several decades, the origin of the CDW phase transition remains somewhat controversial, in part due to the mechanism being dependent on the material. Greater understanding of this peculiar condensed matter phenomenon will not only be of academic interest, but may lend further insight into the mechanisms behind high temperature superconductivity.


The student will directly image the structural changes that candidate 2D metal dichalcogenides undergo during CDW phase changes, while simultaneously correlating with the I-V measured sample resistance. This will require combining a TEM-compatible 2D material device with in-situ temperature control, using a biasing cryo holder for cooling transitions, and a heating holder for heating transitions. The student will thus be able to directly image the phase transition while they simultaneously adjust its temperature.


The student will be aided by the advanced device fabrication, material synthesis, and TEM characterisation facilities available within the Department, and will be able to interact with experts in condensed matter phenomenon (experimental and theoretical), electron microscopy, and 2D material synthesis and device fabrication. 

Please also see the Department's own webpage for the latest advertised projects, as well as for details for how to apply, funding routes, and details of the Physics PhD programme.