Molecular microscopy and spectroscopy with graphene
Supervisors: Neil Wilson (Neil.Wilson@warwick.ac.uk) and Giovanni Costantini (G.Costantini@warwick.ac.uk)
Increasingly science and technology are being pushed down to the level of understanding and manipulating processes
and structure at the atomic and molecular levels. This is equally true for electronics and biology and is pushing the
frontiers of our understanding of physical and chemical phenomena. Studying the structure of individual molecules
and molecular assemblies requires advanced microscopy techniques and the
ability to deposit and define molecules on surfaces under extremely controlled
conditions. In the past this has been the remit of high resolution scanning probe
microscopy, in particular scanning tunnelling microscopy (STM) often under
ultra-high vacuum (UHV) conditions. This technique is capable of producing
exquisite images of individual, flat, molecules on atomically smooth surfaces,
revealing structural and electronic information. As a strictly surface technique,
STM struggles to provide the same resolution as the systems become more
complex and three-dimensional. In addition, as a scanning probe technique it is
usually slow with limited image sizes, making time resolved imaging a highly
specialised area and limiting statistical analysis.
An alternative imaging technique that also has the capability of atomic resolution Fig. 1: STM image of self-assembled layer of
is transmission electron microscopy (TEM). Over the last ten years advances in terephthalic acid on graphene on copper.
aberration corrected TEM have made atomic resolution imaging of crystalline Inset, STM image of bare graphene on
inorganic materials routinely achievable. Indeed it is nowadays possible to not copper.
only resolve where the individual atoms are but also to chemically analyse them. However, TEM gains structural
information by passing a beam of electrons through a sample, in order to study a molecule it must be supported on a
substrate. Almost inevitably the substrate is thicker than the molecule and
hence the image contrast is dominated by the substrate and the molecule is
not resolved. Recently, a critical breakthrough has been made. Single atom
thick substrates such as graphene have been demonstrated as TEM
supports, enabling individual molecules to be imaged on a surface by TEM
with atomic resolution. This provides a tremendous opportunity to develop a
new field, that of atomic resolution TEM for molecular surface science.
Here at the University of Warwick we are ideally placed to grasp this
opportunity. We have recently acquired a state-of-the-art double aberration
corrected TEM, housed in a purpose built microscopy suite, and have
demonstrated expertise in high resolution TEM of single molecules. We have
Fig. 2: TEM image of suspended monolayer
pioneered the application of functionalised graphene TEM supports and now
graphene. The image has been false-coloured
have additional expertise in chemical vapour deposition of graphene for the
and rendered for artistic effect.
fabrication of ‘pristine’ graphene TEM substrates. We have long-standing
experience in molecular surface science, with facilities for and expertise in substrate preparation, UHV molecular
deposition and UHV-STM.
The aim of this project will be to develop the controlled deposition of individual molecules, self-assembled molecular
networks, and molecular thin films directly onto suspended graphene membranes for their subsequent study by high
resolution microscopy. Direct comparisons will be made between STM and TEM, including both structural and
spectroscopic information (electronic from STM and chemical from TEM). For both STM and TEM, image simulation
from theoretically calculated structures can be compared directly with experimental results to gain further insight. We
expect the results to shed new light on molecular interactions and to lay the foundations for an exciting new research
area. The project will be an interdisciplinary one, building on existing collaborations. It will link the Microscopy Group in
Physics (Dr Neil Wilson, Dr Jeremy Sloan and Dr Ana Sanchez) with Dr Giovanni Costantini’s group in the Chemistry
Department. Candidates should have a good undergraduate degree in either Physics or Physical Chemistry.
Warwick Physics Microscopy Group (http://go.warwick.ac.uk/microscopy)
Dr Giovanni Costantini (http://www2.warwick.ac.uk/fac/sci/chemistry/research/costantini/)