School of Physics, Engineering and Technology
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MSc; PhD (Eindhoven); CPhys MInstP
2007-2008: Research Scientist, Fraunhofer Institute for Laser Technology / Philips Extreme UV GmbH, Germany
2008-2011: Postdoctoral Research Associate, University of York
Research group: York Plasma Institute
Our research activities are presented in the Low-Temperature Plasmas research section of the York Plasma Institute.
Full publication list available in the York Research Database.
Former PhD students
Plasma technologies already form a key part of many of today's multi-billion pound industries such as the nanoscale fabrication of microprocessors, energy efficient lighting, production of solar cells and the deposition of advanced functional coatings. Underpinning the effectiveness of these essential technologies is the unique non-equilibrium environment created within the plasma; including a mix of reactive neutral particles, ions and energetic electrons. Many applications rely on the synergistic interaction between the mix of species created in the plasma and a sample surface; however one of the fundamental challenges in plasma science is tailoring the mixture of reactive plasma species such that they have the desired effect on a target.
Novel cold atmospheric-pressure plasmas can operate into open air, remain at room temperature, and still have the selective desired reactivity characteristics. They have many novel applications ranging from plasma medicine to adhesion enhancement of plastics to green chemistry. As with many plasma applications, key for the effectiveness of these devices is the plasma chemistry, ie exactly what mix of reactive species are delivered to a substrate by the plasma.
The chemistry in these plasmas is largely controlled by the electrons; more precisely the distribution of energies that the electrons have. Different electron energy distribution functions (EEDF) drive differences in the plasma chemistry and therefore in the observed effect on a surface, making the EEDF, and especially control over the EEDF of key importance.
Compared to traditional low-pressure plasmas, atmospheric-pressure plasmas are generated at much higher pressure (in open air), meaning there are many more collisions between plasma particles, severely hindering existing low-pressure EEDF control methods. This project aims to take advantage of a newly developed extremely agile high-voltage pulsed power technology, in which pulse characteristics such as rise time, duration and repetition rate can be varied by the user. With this flexibility, the electrical excitation of the discharge can be used to modify the EEDF and therefore control and tailor the plasma chemistry of the APP. Sophisticated (laser-based) plasma diagnostics and numerical modelling will enable us to understand the underpinning mechanisms of the observed changes in chemistry for different pulse shapes. Air-based chemistries, in particular reactive species such as OH, NO, O3, O and N play key roles in many applications and are the focus of this project.
Non-equilibrium plasma technology underpins many high-tech industries such as nanofabrication of computer chips, deposition of advanced functional coatings and production of solar cells. At the heart of these technologies is the non-equilibrium environment in these plasmas, producing a mix of radical atoms and molecules at low temperature that are then used in the applications. In particular, cold atmospheric-pressure plasmas (APPs) have gained significant interest over recent years because they can operate into open air, remain at room temperature, and still have the selective desired reactivity characteristics. They have many novel applications ranging from plasma medicine to green chemistry and food safety.
One of the main challenges in this field is the fact that the mix of radicals changes between the plasma where it is produced and the surface where the reactions for the application happen. Short-lived, highly-reactive radicals that are created inside the plasma react to form longer-lived species downstream from the plasma. It is not just the chemistry inside the plasma that needs to be understood and controlled, importantly the processes occurring between the plasma and the surface need to be taken into account as well. In addition, it is nearly impossible to create a single radical species in a plasma, there is always a mix of different radicals, limiting the selectivity of the induced reactions, making it hard to design optimal plasma parameters for applications.
This project focuses on developing devices that deliver a single radical species to a surface, enhancing reactions selectivity and enabling a superior control of the intended reaction. These systems are very well-controlled which means the underpinning plasma reaction and transport mechanisms can be studied and understood in detail, providing critical information for the design of efficient plasma sources for applications.
In particular, this project takes a novel approach and aims to use so-called mediator molecules to harvest the different short-lived radicals from the plasma and create a single, stable radical species that will be transported to the surface. Radical species and densities will be characterised using sophisticated (laser-based) plasma and radical diagnostics. With this technology, a well-controlled radical flux can be produced, enabling studies into the reaction pathways underpinning applications in plasma medicine and food safety.
School of Physics, Engineering and Technology
University of York
Tel: +44 (0)1904 324904
Fax: +44 (0)1904 322214
Room: GN/010, York Plasma Institute