Extreme Nanowires: Structural and Functional properties of Filled Single Walled Carbon
Nanotubes
Supervisors: Jeremy Sloan and Ana M Sanchez (Microscopy Group)
'Extreme Nanowires' formed by filling single walled
carbon nanotubes can be constrained to as little as 3x3,
1,2,3
2x2 and even 1x1 atomic layers in cross section,
spanning a single rocksalt unit cell down to an individual
row of atoms (Fig. 1). As such, these materials represent
the smallest ordered size scale possible in terms of
scalable nanomaterials fabrication. In some instances
these low-dimensional crystal structures form entirely
new crystalline forms and often present with profoundly
modified physical properties, typically expanded band
gap with more highly discretised densities of states and
modified optical properties, measurable by Raman
4,5
spectroscopy. Very often such crystals also undergo
'Phase Change (PC)' behaviour, morphing from one
crystalline form to another (or from a crystalline to a noncrystalline state), often with a local change in resistivity
or conductance. This work potentially has profound
implications for the fabrication of highly dense memory
2,6
storage devices.
Forming nanowires on such small physical scales
presents unique and benchmarking challenges for high
performance electron microscopy and spectroscopy as
these must perform at the level of single atom sensitivity.
The successful applicant will have an opportunity to
contribute to a world-leading experimental project on
synthesis and characterisation of Extreme Nanowires by
state-of-the-art
electron
microscopy
and
other
characterisation methodologies, e.g. XPS, solid state
Fig. 1 (a) Atomically regulated 'Extreme Nanowires' NMR and Raman spectroscopy. A major goal will be to
templated by SWNTs (l to r): 3x3 KI, 2x2 KI; 1x1 CsI1,2,3; determine the physical properties in several respects that
trigonal semiconducting P42/m (rod) symmetry HgTe5 and are quantitative: (i) in terms of their 3D crystallography;
2x2 semiconducting SnSe2 (b) and (c) HRTEM images of (ii) in terms of their electronic structure; (iii) in terms of
highly ordered 2x2 SnSe and 1x1 CoI2 extreme their quantitative imaging properties (i.e. vis-a-vis
nanowires. (d) Low dimensional lattice phonons bonding); (iv) in terms of how all these characteristics
measured by Raman Spectroscopy from an extreme change over time; and (v) other possibilities. The
nanowire made from semiconducting HgTe.4,5 This new successful applicant will also interact with Warwick's
crystalline form of HgTe (inset) only exhibits this unique world class Theory Group (Dr. David Quigley and Dr.
optical behaviour at low dimension and is a consquence Peter Brommer (Engineering), our Partner Theory Group
of the rod symmetry (i.e. P42/m of the nanowire.4
in Cambridge Physics (Dr. Andrew J. Morris) and also
the high performance Raman spectroscopy group of
Professor David Smith of Southampton Physics. This work may also involve travel to project partners in
Cambridge, Southampton, Nantes, Poland and Japan. Interested students should contact
j.sloan@warwick.ac.uk (Tel. 01246 523392).
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(2000).
[2] R. Carter, M. Suyetin, S. Lister, M. A. Dyson, H. Trewhitt, S. Goel, Z. Liu, K. Suenaga, C. Giusca, R. J. Kashtiban, J. L. Hutchison, J. C.
Dore, G. R. Bell, E. Bichoutskaia, J. Sloan, Dalton Trans., 43, 7391 (2014).
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9044 (2014).
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Rev. Lett., 96, 215501 (2006).
[6] C. Giusca, V. Stolojan, J. Sloan, F. Bonert, H. Shiozawa, K. Sader, M. Rummeli, B. Buchner, S.R.P. Silva, Nano Lett., 13, 2040 (2013).