Towards Current Density Mapping of Ferroelectric Domain Walls with a Nitrogen Vacancy Microscopy

"The project aims to leverage the unique advantages of nitrogen-vacancy (NV) magnetometry within the CQMT department at Queen's University Belfast, where I work alongside a team renowned for its expertise in ferroelectric materials research. NV magnetometry offers exceptional magnetic field sensitivity and the capacity to resolve magnetic textures with nanoscale vectorial precision, making it highly suitable for advancing the study of ferroelectric domain walls in next-generation nanotechnologies.
The project builds on recent developments in ferroelectric systems, where domain wall-based devices, such as ephemeral transistors and neuromorphic logic systems, show promise due to their reduced dimensionality and enhanced conductivity compared to conventional magnetic memory technologies. These devices are based on the dynamic movement, creation, and annihilation of domain walls under external stimuli, including strain gradients, electric and magnetic fields. However, challenges such as reproducibility, conductivity limitations, leakage currents, and ferroelectric fatigue still need to be overcome for these systems to be practical and commercially viable.
Traditionally, conductive atomic force microscopy (c-AFM) has been the primary method for studying domain wall conductance, however c-AFM faces limitations including tip degradation, environmental sensitivity, and contact-related artifacts, which reduce the accuracy and reproducibility of its measurements. To address these issues, my project proposes shifting the focus from direct charge measurements to detecting the magnetic fields produced by charge flow along these domain walls. By using NV magnetometry, which can detect magnetic fields at nanoscale resolutions, this approach promises to provide a non-invasive, reproducible alternative to c-AFM for characterizing domain wall conductivities. Ultimately, this work aims to integrate NV magnetometry with the CQMT's established research framework, enabling reproducible, precise insights into ferroelectric domain wall behaviour and advancing the potential of ferroelectric systems in future nanotechnology applications.

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Academic
- The renewal will create 50 doctoral researchers with high level technical abilities and sophisticated managerial, leadership and personal effectiveness skills ready to take up employment in industry (with partners or beyond) or embark on academic careers.
- The programme will foster multidisciplinary perspectives in the cohorts which will allow them to address challenges either in research areas directly aligned to the PIADS CDT or beyond e.g. in ICT, Healthcare Technologies and sensing.
- Through the PIADS ecosystem academic staff and research groups will foster and form new collaborations leading to research outputs and impact, funding proposals and knowledge transfer.
- PIADS will provide career enhancing opportunities for its academic community, from established academics (advancement) to Early Career academics (supervisory experience and building research profile).
- PIADS will influence the delivery of other postgraduate programmes in the Universities by raising standards and expectations of the postgraduate experience through its cohort based training programme.
- The CDT will foster greater institutional collaboration through jointly awarded research degrees.

Industrial
- PIADS will bring together key companies who form a complete UK manufacturing supply chain for HAMR data storage technology.
- PIADS will drive the development and adoption of low-cost heterogeneous photonic integration technology that can be exploited not only in HAMR but also in multiple markets.
- The PIADS anchor tenant model will impact industry in multiple ways e.g. by facilitating co-creation of PhD/EngD projects, providing an ecosystem that links micro businesses and SMEs through to multinationals, and producing highly skilled doctoral researchers to meet recruitment needs for continued growth.

Societal
- PIADS Engagement & Outreach will continue to deliver its extensive programme of public engagement & outreach e.g. participation in European Researchers' Night, the N. Irish and Glasgow Science Festivals, the STEM Ambassador Programme, industry seminars and workshops and networking. These activities allow the cohorts and the public to interact with the science and technology of PIADS while respecting principles of Responsible Research and Innovation.

Economic
- PIADS will allow the industry partners to recruit skilled and qualified staff that support their respective plans for growth.
- PIADS will support UK economic activity in a sector that has 3X the average national productivity per worker.
- PIADS will support Seagate Technology in its plans to incorporate photonic integration into its current products thereby securing the future of some 1400 people in manufacturing and R&D, which contributes around £100M GVA p.a. to the UK economy in one of its most deprived areas.
- PIADS will engender the creation of an indigenous UK supply chain for low cost photonic integration technologies.
- PIADS will support the industrial partners to exploit outcomes related to their future market strategies, facilitating growth opportunities in a variety of sectors e.g. IQE, CST, KNT, Fraunhofer in ICT, Oxford Instruments, Yelo in scientific and engineering instrumentation, and Causeway Sensors and Cirdan Imaging in medical technology.