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Centre for Materials Physics

Past Listings - CMP Seminars, Meetings and Events

CMP Seminars

9th June 2010, 14:15, PH30, Rochester Building

Post-Graduate Mini Symposium

A series of talks given by year 3/4 CMP postgraduate students

9th June 2010 Ph30, Rochester Building Durham University

 

2:15 - 2:40:Fabrication, Characterisation and Possible Enhancement of the Low Temperature Superconductor Niobium Carbonitride

M.J. Raine

Abstract: We have fabricated the low temperature superconductor niobium carbonitride (NbCN) in bulk form with a transition temperature of ~ 17.63 K and an upper critical magnetic field of ~    10.7 T.  The fabrication process used to produce this material will be critically discussed and compared to alternative methods with an emphasis on future batch production.  Limited data describing the superconducting properties of NbCN are available in the literature so our most recent characterisation data will be presented and our interest in this data made clear.  The critical temperature of this material is sufficiently high for applications if its upper critical magnetic field can be improved.  The way in which we intend to achieve this improvement will be discussed.

 

2:45 - 3:10: Exciton-Polaritons in Sub-Micron Spheres

C.E. Little

Abstract: An exciton-polariton is a quasiparticle formed from the coupling between an exciton and a photon. Exciton-polaritons confined in planar microcavities can produce a polariton laser.  In this talk I will discuss the necessary requirements of a microcavity to support polariton lasing, the suitability of spherical microcavities for polariton lasing and the theoretical results that have been obtained for this geometry.

 

3:15 - 3:40:  Charge and Orbital Order in Iron Oxides

S. R. Bland

Abstract: Resonant x-ray diffraction (RXD) provides an ion specific probe of the long range electronic order present within many materials. Such a technique is ideally suited to studies of charge and orbital order. Here, we present RXD results from iron oxyborate (Fe2OBO3) and multiferroic lutetium ferrate (LuFe2O4).

 

Tea Break

 

4:00 - 4:25: From the Origins of Life to the Formation of Fossil Oil - a whistle-stop tour of the things I've seen using ab initio  electronic structure calculations.

D.L. Geatches

Abstract: First principles electronic structure calculations using density functional theory (DFT) and plane waves are becoming increasingly popular computational tools to investigate non-traditional- physics systems. This is due to an increase in the efficiency of coding, the accuracy of applied theory and the processing power available. Here will be presented some examples of the use of these tools:- an investigation of the possible origins of biological chirality; an attempt to identify the reaction mechanism of the formation of a hydrocarbon from a fatty acid and the characterisation of a transition state using  phonon calculations.

 

4:30 - 4:55: Understanding the dynamics of charge generation in Polythiophene/PCBM blends

Edward W. Snedden

Abstract: Recent developments have allowed the efficiency of photovoltaic devices based on conjugated polymers to pass 5%, leading to great anticipation that they may realise their promise as practical and affordable alternatives in the photovoltaic market.  In order to continue such advances, however, further research must be made in order to fully understand the fundamental properties of the excitations of these systems.

In this talk I will report on the findings of a recent study concerning the dynamics of charge generation in polythiophene/PCBM blends.  Femtosecond pump-probe spectroscopy was used to directly monitor the populations of singlet excitons and free polarons formed in these blends.  Varying the excitation energy and temperature of these measurements revealed the presence of an energetic barrier that must be overcome for charge generation to occur. This barrier was found to directly influence both the total charge yield and the charge generation dynamics, and as such plays a key role in determining the efficiency of polymer solar cells.