Organic molecular semiconductors
Dilute magnetic semiconductors
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The X-ray Spectroscopy group - September 2012
Pictured are Martin Duignan, Cormac McGuinness, Stephen Callaghan, Declan Cockburn and Brian Kennedy (Maxlab)
X-ray Photoemission Spectroscopy (XPS) instrument in CRANN
A monochromated Al-Kalpha Omicron XPS instrument with surface science preparation chamber is a vital part of the TCD equipment base within the group.
Travel to synchrotrons is a necessity for x-ray spectroscopy
There are more than 40 synchrotron or x-ray facilities worlwide of which the TCD group regularly uses five. These are Maxlab in Sweden, the ALS in California, the NSLS in New York, the Swiss Light Source and Elettra in Trieste.
Martin Duignan at beamline 6.3.2 in the ALS
Martin Duignan observes hysteresis from single atom wide capped cobalt nanowires at beamline 6.3.2 in the Advanced Light Source, Lawrence Berkeley Laboratory, CA, USA.
Beamline I1011, Maxlab, Sweden
Shown is the octupole vector magnet and scattering chamber at Beamline I1011 in Maxlab, Sweden, where much of our magnetic research takes place using the techniques of X-ray Magnetic Circular Dichroism (XMCD).
Group at I1011, Maxlab, Sweden
Pictured are Daniel McNally (TCD), John Cunniffe (TCD) and Iwona Kowalik (Maxlab) in the I1011 beamline hutch at Maxlab. Collaboration with beamline scientists at synchrotrons is essential
Beamline 4.0.2, Advanced Light Source (ALS), Lawrence Berkeley Lab., CA, USA
X-ray Magnetic Circular Dichroism (XMCD) measurements are made at beamline 4.0.2 in collaboration with Elke Arenholz of the ALS, where we have been a frequent visitor.
Beamline I511-3, Maxlab, Sweden
Fine adjustments needed for X-ray Emission Spectroscopy (XES) at the I511-3 XES and RIXS endstation at Maxlab. Pictured are Brendan Arnold (left) and Brian Kennedy (right)
Beamline 7.0.1 at the ALS, Lawrence Berkeley Lab., CA, USA
In front of the rack are Per Anders Glans, Timothy Learmonth and Brian Kennedy. Behind the equipment rack is the XES spectrometer and chamber at beamline 7.0.1 at the Advanced Light Source (ALS). Fortune cookies from past chinese meals decorate the rack!
National Synchrotron Light Source (NSLS), Brookhaven Lab., New York
Our group has been a frequent user of beamline X1B at the NSLS in Brookhaven National Laboratory, New York, in collaboration with the Boston University group of Kevin Smith. The geese pictured are an even more regular visitor to the NSLS.
At beamline X1B, NSLS, Brookhaven Lab., New York
The Boston University X1B endstation with organic molecular beam deposition chamber and x-ray emission spectrometer is pictured with Nikos Peltekis, Halvar Trodahl, James Downes and Satheesh Krishnamurthy (left to right)
Scientific discussion at beamline X1B, NSLS, NY, USA
James Downes (Macquarie University) and Nikos Peltekis discuss XES and RIXS from organic molecular semiconductors while at beamline X1B of the NSLS.
Organic molecular beam deposition chamber at X1B beamline
The filament in the manipulator is being degassed in preparation for an organic thin film deposition for in-situ measurements of the x-ray emission spectra (XES) of organic molecular semiconductor materials at the X1B beamline at the NSLS in New York.
ADRESS beamline at the Swiss Light Source, Paul Scherrer Institut
The world leading beamline for RIXS measurements at the Swiss Light Source.
The TCD group at the ADRESS beamline in the Swiss Light Source
From the left is Brian Kennedy, Declan Cockburn and Thorsten Schmitt (PSI), the beamline manager
X-ray Spectroscopy Group photo from 2008.
Back: Daniel McNally, Nikos Peltekis. Front: Brian Kennedy, Patrick Grace, Cormac McGuinness, Iggy McGovern, Brendan Arnold.
Research: (See group photos if within TCD)
Proposed new PhD projects to begin in autumn 2013
Templating of organic thin film growth: organic molecular semiconductors, nanomeshes and graphene nanoribbons
Controlled structured growth of organic materials, organic molecular semiconductor thin films as well as
graphene in particular, is of importance for future devices where either interfaces or local intermolecular forces
dominate in determining the structure and, as it turns out, the most useful device characteristics.
This project will seek to perform measurements of the adsorption, chemical bonding and electronic
structure of organic molecular semiconductor materials forming either heteroepitaxial organic thin films on
inorganic semiconductor or metal surfaces, or in the formation of covalently bonded organic nanostructured
networks on inorganic semiconductor or metal surfaces. Where possible real-time in-situ measurements will
be made to probe intermolecular forces in thin films. Of particular interest is growth templating on stepped or
terraced vicinal single crystal metal surfaces which may allow for useful regular nanoribbons of graphene to
be formed by MOCVD. Associated density functional theory calculations of adsorption, electronic structure,
and x-ray spectroscopy on these surfaces may play a significant part of this project.
Measuring adsorption, chemical bonding and electronic structure of organic
molecular semiconductors or thin films requires ultra high vacuum chambers
organic molecular beam deposition or MOCVD growth and XPS or UPS
photoemission, all available in TCD. Other x-ray spectroscopic techniques
are available at international synchrotron radiation facilities, while real-
time in-situ measurements, as well as scanning probe measurements of
these interfaces, surfaces and films to occur in collaborators laboratories.
Research will be in collaboration with groups in Chemistry (G. Duesberg),
Dublin City University (A. Cafolla), Aberystwyth, Wales (A. Evans) and
Boston U. (K. Smith) with measurements at synchrotron radiation facilities
such as MAXLAB in Sweden or National Synchroton Light Source, NY USA.
Resonant inelastic x-ray scattering - Probing local electronic structure and chemical bonding in transition metal compounds
To measure the symmetry dependent resonant x-ray emission spectroscopy or resonant inelastic x-ray scattering for a variety of structurally similar transition metal oxides and fluorides of formula unit MA2, where excitations at the anion K-edge exciting the anion A 1s electron allows us to probe the anion A 2p densities of states.
Defects can be created in transition metal oxide (TMO) thin films or bulk samples, e.g by high temperature annealing, or by oxidation or reduction of the surfaces in ultra high vacuum. The distribution of these defects can then be controlled by applying electric fields, where the migration of these defects is called electromigration. With defect density gradients established the resultant optical properties are also changed (electrocoloration). The conductivity of defect rich TMOs is significantly changed, and the local physical and local electronic structure surrounding these defects will be probed. Local physical structure can be probed in TCD using electron microscopies. Local electronic structure will be probed by synchrotron radiation based x-ray emission and x-ray absorption and resonant inelastic x-ray scattering (RIXS) spectroscopies at the Advanced Light Source, Lawrence Berkeley Laboratory, California or MAXLAB in Sweden, among others.
- Click on image of project to download complete description.
Ongoing research themes:
Please contact me by e-mail, phone or knock on my door if you are interested in learning more about any of these projects.
Novel element-selective symmetry, polarisation and state resolved investigations of chemical bonding in rutile metal oxide and fluoride systems
The electronic structure of a class of crystalline solids will be investigated through a novel application of
polarisation dependent synchrotron radiation based resonant soft x-ray emission spectroscopy and x-ray
absorption spectroscopies to obtain element specific, symmetry and state selective measurements of the
occupied partial density of states or occupied molecular orbitals of these solids. Systematic investigations
of the chemical bonding in these rutile systems can thus be carried out and compared to electronic
bandstructure calculations. Opportunities then exist to examine the bonding within these systems to
alternative transition metals substitutionally doped onto the cation sites in these rutile systems.
X-ray magnetic dichroism of nanoscale magnetism in atomic wires protected by capping layers
Atomic wires of cobalt, possessing unusual magnetic properties, have been successfully grown on
platinum single crystal surfaces but, to be useful, such nanowires must be capped by ultra-thin films to
protect them from contamination. The interfacial region formed by capping will affect the properties of
these nanoscale magnetic structures; for certain capping layers and thicknesses enhanced Curie
temperatures are expected. X-ray magnetic circular dichroism spectromicroscopy will be used to probe
the magnetisation of these atomic wires on an element and electronic orbital specific basis, to
complement and extend new non-linear magneto-optic studies of the same advanced materials.
In collaboration with Prof. John McGilp of the Surface Physics Group.
Electronic structure of magnetic semiconductor materials: element-specific soft x-ray spectroscopies
The project on electronic structure of magnetic semiconductors as measured by x-ray absorption and emission spectroscopy
is already underway, but interested students are still invited to apply.
Synchrotron X-ray Spectroscopic Investigations of Electronic Structure in Organic Semiconductors
The project on organic molecular semiconductors has started some time ago but interested
students are still invited to apply.
- Postgraduate funding:
Postgraduate funding is available through The
Irish Research Council (formerly IRCSET) Postgraduate Research Scholarship Scheme.
Such postgraduate funding is at a rate of €16,000 per annum.
(The next round of applications have opened and are closing in mid February.)
Visit the Irish Research Council website for
details on post graduate funding, this is open to all EU citizens.
TCD Scholarships are also available as partial fellowships.
Further details on funding and on postgraduate fees may be found on the
School of Physics website.
- Beamtime funding:
Funding for experimental beamtime at the synchrotron facilities is often obtained separately through the facilities themselves
and is currently funded under the CALIPSO FP7 Integrating Activity.
X-ray emission group
There are currently 2 students studying under my direction. They are:
I have graduated five students from my research group
- Stephen Callaghan
- Martin Duignan
I have closely worked with two other students in their Ph.D. projects under other supervisors within Trinity College Dublin as well as one external to Trinity.
- Declan Cockburn, Ph.D. - now working for ASML, Eindhoven, Holland
- Brian Kennedy, Ph.D. - now working at MAX-lab, Lund, Sweden.
- Nikolaos Peltekis, Ph.D. - now working in Intel, Leixlip and Arizona.
- Brendan Arnold, M.Sc. - now studying for Ph.D. at Bristol University
- Daniel McNally, M.Sc. - now studying for Ph.D. at State University of New York, Stonybrook
- Brendan Holland, Ph.D. - supervised by Prof. McGovern, TCD.
- John Cunniffe, Ph.D. - supervised by Prof. McGilp, TCD.
- Timothy Learmonth, Ph.D. - supervised by Prof. Smith, Boston University.
These projects will be carried out in collaboration with the following groups within Trinity:
And other collaborators within Ireland:
I also collaborate with the following international groups:
The synchrotron radiation facilities and beamlines at which I have been working are:
- National Synchrotron Light Source (NSLS),
Brookhaven National Laboratory, Long Island, NY, USA.
- MAX-lab, Lund, Sweden
- Advanced Light Source (ALS), Lawrence Berkeley Laboratory, Berkeley, CA, USA
Soft x-ray spectroscopy on the web: