Professor Jason Smith
Department of Materials
Tel: +44 1865 273700 (switchboard)
Fax: +44 1865 273789 (general fax)
Photonic Nanomaterials Group
Leader of the Photonic Nanomaterials Group (PNG) in which research is focused on optical and electronic properties of solid state nanostructures for applications such as optoelectronics devices, quantum information processing and photovoltaics. At present the Group’s research involves two such systems - semiconductor nanocrystals and colour centres in diamond which we investigate using luminescence-based optical techniques. More information about our research can be found in the project descriptions below, or on the PNG website.
High Q optical microcavities for solid state cavity QED
P. Dolan, Dr. G. Hughes, Dr. J.M. Smith
In this project we are developing large arrays of high quality tunable optical microcavities and using them to modify the photon emission properties of nanomaterials such as diamond colour centres and semiconductor nanocrystals. The project focuses on the basic science of the emitter/cavity quantum systems, and explores their use as single photon sources, microlasers, and in a range of sensing and spectroscopic applications. Collaborators include the University of Strathclyde, the University of Bristol, and the University of Melbourne.
Enhancing the efficiency of thin film solar cells using optical confinement
M. Wincott, A. Powell, Dr. H.E. Assender, Dr. A.A.R. Watt, Dr. J.M. Smith
Thin film solar cells offer an inexpensive means to generate clean energy, but current efficiencies are limited to around five percent, about three times lower than commercial polycrystalline silicon cells. One of the main reasons behind the low efficiency is that a tension exists between the desire to absorb as much as possible of the incident light, in which case the optical path length should be thick (at least several hundred nanometres), and the desire to extract the photogenerated charge carriers efficiently from the cell, in which case the exciton transport path length should be short (no more than a few tens of nanometers). Most attempts to solve this problem involve using a thick cell, and focusing the advanced aspects of cell design on building in some means for ensuring a short transport path length. Here we take the opposite viewpoint; that the optical path can be elongated for a given cell geometry by the use of wave guiding and cavitation, thereby reducing the burden placed on the transport related features of the device. This new project involves the design, fabrication, and testing of devices that explore this theme by employing inexpensive approaches to encourage light to propagate in the plane of the film.
Roll-to-roll processing of organic electronics
Dr G.A.W. Abbas, Z. Ding, Dr. H.E. Assender
Electronics components that can be manufactured using roll-to-roll processing offer the possibility of lower cost devices as well as those that might be mechanically flexible in use. Roll-to-roll (R2R) processing, using a flexible substrate (typically a polymer film) allows for cheap production of many components very rapidly, with low energy requirements. Key areas of exploitation of this technology include flexible displays, but there is also a wealth of lower-cost applications. Tagging and tracking of fast moving consumer goods is an example technology that truly exploit the very low-cost nature of the production and in which the manufacturing is closely linked to the manufacturing routes currently exploited for e.g. packaging technologies. This project seeks to exploit the existing industrialised technology of vacuum R2R processing, widely used for example in the packaging industry, to develop the manufacture of very low cost organic field-effect transistor (OFET)-based devices and circuits. This manufacturing route, like solvent based systems, is cheap and provides flexible product, and we can exploit high electrical mobility molecular semiconductors. Additional advantages of the solvent-free vacuum processes include: a) likely enhanced web-speed, b) integration with vacuum-based metal deposition for conducting channels, and metal or ceramic deposition for barrier layers and possible interfacial modification, and c) the ability to deposit multiple thin layers to build up device structures without solvent interactions with underlying layers. The project will exploit our existing R2R web processing facility to explore the principal manufacturing challenges to R2R vacuum production of OFET devices: 1) selection and adaptation of materials to vacuum deposition integrated with design of suitable circuitry, 2) patterning of the semiconductor and insulator layers to allow the formation of circuit connections between devices and 3) reliability of manufacture to be able to produce arrays of multiple transistors for circuits. It will allow us to explore and develop the deposition of molecular semiconductor and dielectric materials and then the subsequent reliability and thermo-mechanical resilience of the resulting product such that it might need to withstand, for example, during a lamination process.
3 public active projects
P. R. Dolan, G. M. Hughes, F. Grazioso, B. R. Patton, and J. M. Smith, Femtoliter tunable optical cavity arrays, Optics Lett. (in press).
F. Grazioso, B. R. Patton, and J. M. Smith, A high stability beam-scanning confocal optical microscope for low temperature operation, Review of Scientific Instruments 81, (2010).
C. A. Cattley, A. Stavrinadis, R. Beal, J. Moghal, A. G. Cook, P. S. Grant, J. M. Smith, H. E. Assender, and A. A. R. Watt, Colloidal synthesis of lead oxide nanocrystals for photovoltaics, Chem. Comm. 46, 2802 (2010).
R. M. Beal, A. Stavrinadis, J. H. Warner, J. M. Smith, H. E. Assender, and A. A. R. Watt, The molecular structure of polymer-fullerene composite solar cells and its influence on device performance, Macromolecules 43, 2343 (2010).
A. Stavrinadis, J. M. Smith, C. A. Cattley, A. G. Cook, P. S. Grant, and A. A. R. Watt, SnS/PbS nanocrystal heterojunction photovoltaics, Nanotechnology 21, 185202 (2010).
A. Stavrinadis, S. Xu, J. H. Warner, J. Hutchison, J. M .Smith and A. A. R. Watt, Superstructures of PbS nanocrystals in a conjugated polymer and the aligning role of oxidation, Nanotechnology 20, 445608 (2009).
D. J. Keeble, E. A. Thomsen, A. Stavrinadis, I. D. W. Samuel, J. M. Smith, and A. A. R. Watt, Paramagnetic point defects and charge carriers in PbS and CdS nanocrystal polymer composites, J. Phys. Chem. C 113, 17306 (2009).
S. C. Benjamin, B. W. Lovett, and J. M. Smith, Prospects for measurement based quantum computing using solid state spins, Laser & Photonics Reviews, 3, 556 (2009).
P. K. Santra, R. Viswanatha, S. Daniels, N. L. Pickett, J. M Smith, P. O'Brien and D. D. Sarma, Investigation of the internal heterostructure of highly luminescent quantum dot - quantum well nanocrystals, J. Am. Chem. Soc. 131, 470 (2009).
B. A. Fairchild, P. Olivero, A. D. Greentree, F. Waldermann, R. A. Taylor, J. M. Smith, S. Rubanov, S. Huntington, B. Gibson, D. N. Jamieson, and S. Prawer, Fabrication of ultra thin membranes from single crystal diamond for photonic and NEMS applications, Advanced Materials 20, 4793 (2008).
A. Stavrinadis, R. Beal, J. M. Smith, H. E. Assender, and A. A. R. Watt, Direct formation of PbS nanorods in a conjugated polymer, Advanced Materials 20, 3105 (2008).
S. H. Kim, P. H. Sher, Y. B. Hahn, and J. M. Smith, Luminescence from single CdSe nanocrystals embedded in ZnO thin films using atomic layer deposition, Nanotechnology 19, 365202 (2008).
P. A. Dalgarno, J. M .Smith, J. MacFarlane, B. D. Gerardot, K. Karrai, A. Badolato, P. M. Petroff, and R. J. Warburton, Coulomb interactions in single charged self-assembled quantum dots: Radiative lifetime and recombination energy, Phys. Rev. B 77, 245311 (2008).
P. A. Dalgarno, M. Ediger, B. D. Gerardot, J. M. Smith, S. Seidl, M. Kroner, K. Karrai, P. M. Petroff, A. O. Govorov, and R. J. Warburton, Optically induced hybridization of a quantum dot state with a filled continuum, Phys. Rev. Lett. 100, 176801 (2008).
P. H. Sher, J. M. Smith, P. A. Dalgarno, R. J. Warburton, X. Chen, P. J. Dobson, S. M. Daniels, N. L. Pickett, and P. O'Brien, Power law carrier dynamics in semiconductor nanocrystals at nanosecond time scales, Appl. Phys. Lett. 92, 101111 (2008).
S. Seidl, M. Kroner, P. A. Dalgarno, A. Hogele, J. M. Smith, M. Ediger, B. D. Gerardot, J. M. Garcia, P. M. Petroff, K. Karrai, and R. J. Warburton, Absorption and photoluminescence spectroscopy on a single self-assembled charge-tunable quantum dot, Phys. Rev. B 72 195339 (2005).
P. A. Dalgarno, J. M. Smith, B. D. Gerardot, A. O. Govorov, K. Karrai, P. M. Petroff, and R. J. Warburton, Dark exciton decay dynamics of a semiconductor quantum dot, Phys. Stat. Solid. A-Applications and Materials Science 202 p.2591-2597 (2005).
A. J. Moore, J. Smith, and N. J. Lawson, Volume three-dimensional flow measurements using wavelength multiplexing, Optics Lett. 30, p.2569 (2005).
J. M. Smith, P. A. Dalgarno, R. J. Warburton, A. O. Govorov, K. Karrai, B. D. Gerardot and P. M. Petroff, Voltage control of the spin dynamics of an exciton in a semiconductor quantum dot, Phys. Rev. Lett. 94, 197402 (2005).
M. Ediger, P. A. Dalgarno, J. M. Smith, B. D. Gerardot, R. J. Warburton, K. Karrai and P. M. Petroff, Controlled generation of neutral, negatively-charged and positively-charged excitons in the same single quantum dot, Appl. Phys. Lett. 86, 2119209 (2005).
B. Urbaszek, E. J. McGhee, J. M. Smith, R. J. Warburton, K. Karrai, B. D. Gerardot, J. M. Garcia and P. M. Petroff, Charged excitons in individual quantum dots: effects of vertical electric fields and optical pump power, Physica E 17, 35 (2003).
J. M. Smith, P. A. Dalgarno, B. Urbaszek, E. J. McGhee, G. S. Buller, G. J. Nott and R. J. Warburton, Carrier storage and capture dynamics in quantum-dot heterostructures, Appl. Phys. Lett. 82, 3761 (2003).
M. A. Malik, P. O'Brien, S. Norager and J. Smith, Gallium arsenide nanoparticles: synthesis and characterisation, J. Mater. Chem. 13, 2591 (2003).
J. M. Smith, G. S. Buller, D. Marshall, A. Miller and C. C. Button, Microsecond carrier lifetimes in InGaAsP quantum wells emitting at lambda=1500 nm, Appl. Phys. Lett. 80, 1870 (2002).
J. M. Smith, P. A. Hiskett, I. Gontijo, L. Purves and G. S. Buller, A picosecond time-resolved photoluminescence microscope with detection at wavelengths greater than 1500 nm, Rev. Sci. Instrum. 72, 2325 (2001).
J. M. Smith, P. A. Hiskett and G. S. Buller, Picosecond time-resolved photoluminescence at detection wavelengths greater than 1500 nm, Opt. Lett. 26, 731 (2001).
P. A. Hiskett, J. M. Smith, G. S. Buller and P. D. Townsend, Low-noise single-photon detection at wavelength 1550 nm.Electron. Lett. 37, 1081 (2001).
S. Pellegrini, G. S. Buller, J. M. Smith, A. M. Wallace and S. Cova, Laser-based distance measurement using picosecond resolution time-correlated single-photon counting, Meas. Sci. Technol. 11, 712 (2000).
P. A. Hiskett, G. S. Buller, A. Y. Loudon, J. M. Smith, I. Gontijo, A. C. Walker, P. D. Townsend and M. J. Robertson, Performance and design of InGaAs/InP photodiodes for single- photon counting at 1550 nm, Appl. Optics 39, 6818 (2000).
Sensing, characterisation and manipulation at the nanoscale using optical microcavities
Professor Jason Smith and Dr Aurélien Trichet
Optical sensing and spectroscopy are powerful tools for detecting and characterising nanoparticles at the single particle level. Pollutants and aerosols or microbiological organisms such as viruses have characteristic optical signatures based on their refractive index, size, and polarisability as well as spectral signatures that allow them to be identified and studied. This project will develop novel optical microcavities as means of confining light such that its interaction with nanoparticles is both strengthened and highly controlled. These microcavities show great potential for the trapping and manipulation of particles, and for particle identification using refractive index and spectroscopic methods. The project will involve fabrication of cavity devices and using them to perform some foundational experiments in this area. The student project is part of a larger effort within the group, in collaboration with Dr Claire Vallance in the Department of Chemistry.
Also see homepages: Jason Smith
Also see a full listing of New projects available within the Department of Materials.