Doctor of Philosophy (PhD) – Slotted photonic crystal waveguides as a platform for surface enhanced Raman detection of hydrogen (AWE and University of St Andrews)

Project Description

The detection of hydrogen gas is important in many industries (petrochemical, civil nuclear, transport etc) due to its highly flammable nature. This need is likely to grow in the near future as hydrogen is used as the fuel of choice in many applications to reduce greenhouse gas emissions. Typically, hydrogen is detected using technologies reliant on chemical interactions with a catalytic material to oxidise the hydrogen to generate a signal. These technologies can be limited by their lack of selectivity and susceptibility to catalytic poisoning by commonly occurring chemicals. They also require a minimum oxygen content to function.

There is a need to have a compact optical solution that is selective, reliable, and able to operate in harsh environments, possibly without the presence of oxygen.

Raman spectroscopy has the capability to selectively detect hydrogen. However due to the extremely low signal levels for the Raman scattering process this technique is yet to be widely commercialised. Some progress has been made for open path detection using sensitive single photon avalanche diodes (SPAD) to detect the extremely small signals, but this methodology is not applicable for confined spaces or sealed vessels where a more compact solution is required. An alternative way to boost the sensitivity of the Raman signal would be to use the evanescent wave effects employed by surface enhanced Raman (SERS). SERS substrates are readily available for use with liquid analytes, particularly for biological specimens. However, these have a limited life, are often single use and require a suitable Raman microscope to measure the SERS signal.

A similar SERS effect should be possible using slotted photonic crystal waveguides (SPCW). These can be fabricated using semiconductor technology and could eventually lead to a full Raman-on-a-chip device.

This project would use models to predict the most suitable semiconductor substrate and excitation wavelength to use for SERS on an SPCW. The design would then be fabricated using the state-of-the-art facilities at St Andrews and tested to demonstrate the ability to detect hydrogen.

The student will be working at the University of St Andrews, supervised by the group of Synthetic Optics, within the School of Physics and Astronomy. The student will have access to the nanofabrication facilities, including multiple cleanrooms, electron beam and optical lithography systems, material deposition such as sputterer, evaporators, etc. Characterisation facilities include scanning electron microscopes, optical setups from the visible to near infrared spectral regions, and material characterisation, e.g. profilometry and ellipsometry. The student will also be part of the wider photonics research environment in the School of Physics and Astronomy, with a cohort of approximately 100 staff and students.

The School of Physics and Astronomy at the University of St Andrews has Juno Champion status (Institute of Physics) which reflects its commitment to family friendly policies and creating a work environment of benefit to all staff and students.

It has flexible and part time working policies for staff and features guidelines for full time vs part time study for students.

The supervision team are happy to discuss these with candidates when desired.

CDT Essential Criteria

A Masters level degree (MEng, MPhys, MSc) at 2.1 or equivalent.

Desire to work collegiately, be involved in outreach, undertake taught and professional skills study.

Project Essential Criteria

This project will cover spectroscopy, the physics of waveguides, gas sensing and fabrication of semiconductor devices so the candidate must have a keen interest in these areas.

A strong desire and ability to put theory into practice to make a difference.

The ability to work as part of a wider team and show initiative when working alone.

Have an interest with working with industrial partners and end users of the resulting technology.

Project Desirable Criteria

Knowledge of setting up optical systems and laser safety

Knowledge of Raman spectroscopy

Knowledge of semiconductor fabrication techniques

The CDT

The CDT in Applied Photonics provides a supportive, collaborative environment which values inclusivity and is committed to creating and sustaining a positive and supportive environment for all our applicants, students, and staff. For further information, please see our ED&I statement: https://bit.ly/3gXrcwg.

Forming a supportive cohort is an important part of the programme and our students take part in various professional skills workshops, including Responsible Research and Innovation, and attend outreach training.