Pure beams of free radicals for studies of radical-surface chemistry

Lead Research Organisation: University College London
Department Name: Chemistry

Abstract

Free radicals, molecules with one or more unpaired electrons, are highly chemically reactive. This high reactivity means that free radicals exert a major influence on the chemistry of any environment in which they are formed, even though they are often not the most abundant species. For example, it is free radical chemistry that controls important atmospheric phenomena such as the ozone hole and the formation of photochemical smog.
The interactions of free radicals with surfaces are thought to be vitally important in controlling the chemistry of formation of thin-films from electrical discharges, so called plasma-assisted deposition. Such thin-films have enormous technological importance in fields such as integrated circuits and solar cells. However, the details of the interactions of the radicals with the surfaces in these film formation processes are not well understood. The major hurdle to investigating this surface chemistry of free radicals is that, currently, there is no general technique available to dose a surface with only the free radical of interest, for example CH. Current radical sources generate the radicals from a precursor gas (e.g. CH from C2H2) and the precursor gas molecules always outnumber the radicals. Thus if a surface was dosed from a conventional radical source, the precursor molecules would be the dominant species on the surface, making it almost impossible to study the interactions of the radical with the surface using standard surface science techniques.
In this application, we propose the development of a new source of free radicals which will generate "clean" beams of the radical species, uncontaminated by the precursor molecule. The source will work by generating negative ions (e.g. CH-), which can be mass selected to form a clean beam. The radicals are then generated from the negative ions by using a laser beam to knock off the electron. This photo-detachment of negative ions will yield a clean beam of the radical species of interest. Calculations given in the proposal show that a practical flux of free radicals can be generated by this methodology.
The clean beams of free radicals can then be used to dose the surface with the radical species, and the surface can be studied using the standard techniques of surface science to reveal the details of the radicals sticking and surface chemistry. We propose to develop the source and then use it to study the radical-surface interactions involved in three technologically important film deposition processes. The chemistry revealed by our investigations will dramatically improve our understanding of what is going on in these industrially relevant surface reactions and allow us to optimize and refine these deposition processes in the light of the chemistry that is occurring.

Planned Impact

In addition to the academic beneficiaries identified above, we have identified three groups of beneficiaries of the proposed research programme:
1) Industrial companies with interests in plamsa deposition.
The central aspect of this research proposal is the development of a new source for generating clean beams of specific radical species, beams uncontaminated by any precursor molecules, and the use of that beam to probe the radical-surface chemistry involved in the, industrially important, field of thin-film deposition from plasmas.
After developing and commissioning the radical beam source, we will use the beam to investigate the radical-surface chemistry relevant to thin-film generation in three industrially important systems: a-C:H, SiCN and Al-ZnO. The consequent improvement in our fundamental understanding (as evidenced by our Project Partners) will stimulate scientifically-founded improvements in the industrial processes. Of particular interest will be our adventurous experiments to investigate new methodologies from growing ZnO:Al films. Our experiments should reveal which chemical species involving aluminium (e.g. AlO) interact most effectively with the surface to generate, for example, layers of the metal.
The above arguments are validated by our Project Partners. For example Ionbond write "... it is essential that we move to a coherent design strategy based on fundamental process and materials understanding, which the current proposal can help to provide. The technique described will allow access to the details of the surface chemistry of free radicals, which are thought to be the critical chemical species in plasma assisted coating processes. It will also provide data of value for rationalizing observed behaviour and predicting improvements in industrially relevant surface chemistry."
2) UK employers
This programme involves the recruitment and training of 2 research workers; specifically 1 PDRA and 1 PhD student. As detailed in the proposal, the career history of previous research workers trained by the applicants shows that they go on to contribute to all spheres of the UK economy. For example, Jon Gingell (UCL PhD, 2004) has gone on to set up "OpenSymmetry", now a leading consulting and integration firm, co-Directed by James Perry (UCL PhD 2005), that offers highly specialized services focused on delivering Sales Performance Management solutions to clients worldwide (http://www.opensymmetry.com).
The employability of our research workers shows the broad appeal of the fundamental and applied skills that these individuals assimilate when involved with projects such as that proposed in this application. Clearly, the problem solving abilities, coupled with numeracy and communications skills, which are developed by research in physical and materials chemistry are highly desirable for successful careers in a broad range of disciplines which contribute to the UK's economy.
3) The general public
The applicants have extensive experience with Public Engagement. The proposed research programme offers an exceptional opportunity for public outreach to demonstrate the key position of the physical sciences, and its interaction with Industry, in the UK's research portfolio. As detailed in the proposal, all of the investigators will add to their portfolio of public outreach by developing a range of presentations (depending on the audience: school children, adults ...) on the role of radicals in the environment (atmospheric and interstellar chemistry, plasmas ...) focusing on the goals of the proposed experiment. The presentations will reveal the fundamental synergy between basic science and industrially-relevant science, as illustrated by the radical beam. A key objective of this programme of outreach would be to develop a display, on radicals and radical surface chemistry, for the Royal Society Summer Science Exhibition.

Publications

10 25 50
 
Description Made first beams of free radicals via photodetachment. We are currently (with funding from the Leverhulme Trust) trying to increase the flux of the parent negative ions to increase the flux of the radical beam. We are also using the surface science changer to study the desorption of small molecules of astrophysical interest from analogues of interstellar dust grains.
Exploitation Route Technology can be used by others interested in radical beams. Data on desorption used by astrophysicists and astronomers

We are currently developing a higher current ion source to generate more intense beams of radicals.
Sectors Energy,Environment,Other

 
Description We now have generated our first beam of O atoms. The beams are still quite weak and we are working on increasing the flux. These results have generated some interest in the plasma etching community. We've won more funding to develop this technique further by increasing the ion flux and this is currently underway.
First Year Of Impact 2017
Sector Other
Impact Types Societal,Economic

 
Description Research Grants
Amount £177,961 (GBP)
Funding ID RPG-2017-309 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2018 
End 03/2021
 
Description Collaboration with group at University Cergy, Paris 
Organisation Cergy-Pontoise University
Country France 
Sector Academic/University 
PI Contribution The aim is to developing better models of reactions on surfaces. Data from our experiments will be moddeled by the French group
Collaborator Contribution Complimentary experiments and modelling
Impact Application for exchange funding for students in progress
Start Year 2014
 
Description Informal Collaboration with Scanwel 
Organisation Scanwel Ltd
Country United Kingdom 
Sector Private 
PI Contribution Our instrument manufacturer Scanwel is interested in contributing to a CDT programme we are developing at UCL. The MD of Scanwel has agreed to contribute to a course on Vacuum design. Ian Owen has agreed to offer a contribution to a CDT in instrument design are developing at UCL. Ian's expertise in vacuum design would be incorporated via some "guest lecture" slots.
Start Year 2013
 
Description "Reactions on Cold Surfaces in the Interstellar Medium" Conference to celebrate the work of Dan Eley, Nottingham April 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact talk at conference to celebrate the life of the surface science pioneer Dan Eley
Year(s) Of Engagement Activity 2016
URL http://www.nottingham.ac.uk/chemistry/events/colloquia/dan-eley-celebration.aspx
 
Description Appearance on Sky at Night 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interviewed on Sky at night about resesarch
Year(s) Of Engagement Activity 2015
 
Description BBC radio 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interview as part of World service programme on ice in space
Year(s) Of Engagement Activity 2017
 
Description Invited talk Caen Chemical Physics conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Plenary lecture at confernece
Year(s) Of Engagement Activity 2015
 
Description Public Lecture, SASP Austria 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact Prize talk to which members of the public were invited

Lots of questions from public
Year(s) Of Engagement Activity 2014
 
Description Public lecture - "pint of Scinece" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact talk as part of the "pint of Science" event
Year(s) Of Engagement Activity 2016
 
Description Public talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Public talk at BBK
Year(s) Of Engagement Activity 2018
 
Description SDSG conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Invited talk
Year(s) Of Engagement Activity 2016
 
Description Seminar at Leeds Univeirsty 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Seminar of beams and ices to Chemistry Department
Year(s) Of Engagement Activity 2017
 
Description Series of talks on Ice and Ions 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Series of talks at Open Days to publicise inter-disciplinarity in Science using our work as an example.
Year(s) Of Engagement Activity 2016,2017
 
Description Talk at Imperial College 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Seminar at Imperial College
Year(s) Of Engagement Activity 2016
 
Description Talk at University -Industry conference on detector methodology 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk about our beam techniques and detector technology to an audience interested in position sensitive detection -academics/industry
Year(s) Of Engagement Activity 2016
URL http://pimms.chem.ox.ac.uk/imagingworkshop.php
 
Description University Seminar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Seminar at Leeds Unviersity
Year(s) Of Engagement Activity 2017
 
Description talk on surface chemistry in the ISM and ion chemistry 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk at Austrian Chemical Physics conference
Year(s) Of Engagement Activity 2018