High-throughput characterisation and inline process monitoring of 2D semiconductor films

The project aim is to support the industrial translation of emerging ultrathin 2D semiconductor materials by developing smart metrology and best-practice approaches to fingerprint and monitor material quality characteristics across entire process pathways. The project brings together expert academic expertise and the National Physical Laboratory (NPL) to form new international metrology strategies. 

Project Description:

Agile discovery and deployment of advanced materials is critical for enabling emerging technologies and driving sustainable economic growth across strategic UK sectors. Yet, development timelines remain frustratingly slow. A key need to accelerate innovation and commercialisation is high-throughput characterisation capability, enabling rapid feedback loops and effective experimental workflows. This project focusses on 2D semiconductors materials, like WS2 and MoS2, motivated by industrial roadmaps [1] that highlight their potential in particular for urgently required new energy efficient computing and AI. These materials offer effective scaling down to mono-layer level, which allows tuning of new properties.[2] The complete exposedness of a monolayer, however, amplifies the significance of intrinsic and extrinsic disorder. Hence, while scalable synthesis approaches have been developed, in particular CVDbased technology, [3] the field is held back by a lack of yield and reproducibility. There is a pressing need not only for basic characterisation standards that can bridge scales from atomic to macro dimensions, but for process-step resolved material monitoring to understand how such materials behave in realistic environments and application conditions. The latter carriers through the entire emergent supply chain.

This project aims to develop a new holistic metrology approach to enable time, process and application driven characterisation and monitoring of such ultrathin semiconductor materials. We propose to bring together different approaches to a hybrid platform that can make full use of integrated data-driven and digital enhancement. This builds on the expertise and prior work of the PIs and reflects the cornerstones of the 2024 “Advanced materials metrology strategy” by the NPL.[4] The initial material focus will be on WS2 and MoS2, and as reference system we propose to use exfoliation that can provide small flakes of high crystalline quality. Using reactive annealing cycles in Ar/H2 or sulphur atmospheres we have relative scale of defectiveness available that we are calibrated (Group of Prof Chhowalla). This will form a baseline to then study CVD and ALD deposited films, that are structurally more complex but also may carry synthesis specific impurities/defects. The films will be made in house but also sourced from leading international partners, including IMEC.[5] The proposed characterisation techniques will be Raman, photoluminescence, AFM, SEM, TEM, XPS and spectroscopic imaging ellipsometry (SIE). We recently developed Kramers-Kronig constrained variational analysis that can address current limitations of SIE for monolayer materials.[6] We also demonstrated the potential of ellipsometric contrast micrography (ECM) to unlock fast sample/reaction mapping. The aim is to bring these techniques together in smart, correlative fashion in order to develop fast screening capability and protocols particularly by SIE and ECM. A first target will thereby be to explore the effects of environmental and process-related exposure to oxygen and water. This is crucial as currently samples are often transferred/handled in/exposed to air, and this can lead to “aging” and significant hitherto non-captured changes in structure and defects. We will also explore the effects of how the measurement exposure itself and substrate choice can change the film properties (photo/ebeam/X-rays), which is crucial to establish reliable protocols.

Supervisors:

1. Stephan Hofmann (sh315@cam.ac.uk)
2. Manish Chhowalla (mc209@cam.ac.uk)

If you are interested in this PhD, we encourage you to contact the project supervisor(s) directly.

Application Deadline:

Applications open until successful candidate is recruited (no later than Summer 2025)

Funding Notes:

This is a fully funded project, part of cohort 2 of the EPSRC CDT in Materials 4.0. CDT. The studentship covers fees (home & international), a tax-free stipend of at least £19,237 plus London allowance if applicable, and a research training support grant.

Candidates of all nationalities are welcome to apply; up to 30% of studentships across the CDT can be awarded to outstanding international applicants. Early applications from interested overseas candidates are encouraged.

The Materials 4.0 CDT is committed to Equality, Diversity and Inclusion. Five countries are represented in cohort 1. We would like to see a more gender-balanced cohort 2, so we strongly encourage applications from female candidates.

Enquiries:

For application-related queries, please contact Ana Talaban-Bailey (ajt69@cam.ac.uk). Please note that each partner of the CDT in Materials 4.0 will have its own application process.

Application Webpage:

https://www.postgraduate.study.cam.ac.uk/courses/directory/pcmmpddnc

There’s an ‘apply now’ button at the top of the right-hand menu.