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The High Temperature Superconductor (HTS) research group focusses on relationships between processing, microstructure and properties of superconducting materials.  Our recent activities include the growth and characterisation of novel iron-based superconductors in thin film form, and advanced microstructural characterisation of single crystals of these materials using techniques such as High-Resolution Electron Backscatter Diffraction (HR-EBSD).  In addition I have an ongoing interest in the processing of thallium-based HTS on flat and curved substrates for a range of device applications. Recent work has focused on grain boundary properties and texture development in Tl-based HTS films and YBCO coated conductors. and a growing area of interest is the development of superconducting meta-materials for novel applications such as near field NMR microscopy.

Growth and characterisation of thin film superconductors
T. Mousavi, Dr. S. Speller, Professor C.R.M. Grovenor
We are growing epitaxial thin films of the recently discovered Fe-based superconducting materials in order to explore how the properties can be controlled and their potential for future exploitation in practical devices. Most of our work is currently on the Fe(SeTe) system, and we make extensive use of TEM, SEM, XRD and EBSD analysis to relate superconducting properties to microstructure. (In collaboration with Dr Gavin Burnell, Leeds University).  Supported by an Oxford University Clarendon Scholarship

Superconducting Metamaterials
J. Janurudin, Dr. S.C. Speller, Dr. C. Stevens*, Professor D. Edwards*, Professor C.R.M Grovenor
This project will study the fabrication, microstructure and properties of oxide/superconducting metamaterials to test the effective medium theory of these composite materials.   Simple resonating elements of Tl-2212 will be fabricated on single crystal ceramic substrates and assembled into volume of metamaterial  with ‘unnatural’ permittivity and permeability values.   (*Engineering Dept., Univ. of Oxford).(Funded by Royal Academy of Engineering, by EPSRC grant EP/I034548, and by a Malaysian Government scholarship [JMJ].)

Superconducting metamaterial devices on curved substrates
Dr. S. Speller
Metamaterials can be designed to exhibit strange electromagnetic properties which do not occur naturally. This project involves making and testing novel microwave devices from superconducting films grown on cylindrical substrates. It will involve the use of a new lithography system and FIB micro-machining, along with techniques for microstructural characterization of the superconducting films such as SEM, AFM and XRD. Device measurements will be carried out with collaborators in Engineering Science.

Characterisation of Fe-based superconductors
Dr. S. Speller, Professor C.R.M. Grovenor, Professor Andrew Boothroyd*
High resolution EDX and EBSD analysis techniques are being applied  to develop a better understanding of the phase separation phenomena that may control the superconducting and magnetic properties of single crystal samples of the Fe-based superconducting family.  *Clarendon Laboratory In collaboration with E. Pomjakushina, K. Conder, Laboratory for Developments and Methods, Paul Scherrer Institut

4 public active projects

Dark, C., Speller, S., Wu, H., Sundaresan, A., Tanaka, Y., Burnell, G. ,Grovenor, C.R.M.: 'Grain boundary properties of T1-2212 and T1-1223 thin films' Ieee Transactions On Applied Superconductivity 15 (2) (2005) 2931-2934.

Dark C.J., Speller S.C., Grovenor C.R.M.: ' The development of bi-epitaxial texture and high grain boundary Jc values in Tl-2212 films on MgO' Supercond. Sci. Technol., 19 (6) (2006) 484-492

Speller S.C., Wu H., Rek Z.U., Bilello C.J., Grovenor C.R.M.: 'Development of microstructure in Tl-2212 thin films and possible influence on microwave surface resistance values' J. Mater. Res. 21 (7) (2006) 1645-1657

Processing of novel topological insulators in thin film form
S.C. Speller / C.R.M. Grovenor

Very recently, a new class of functional materials have been discovered that are bulk insulators with exotic metallic states at their surfaces, called topological insulators.  These materials are particularly exciting because electron transport at these surfaces is insensitive to scattering by impurities, making them attractive for spintronics and quantum computing applications.  This project involves the development of processing strategies for fabricating by sputtering high quality thin films of topological insulators such as Bi2Se3.  X-ray diffraction will be used to study the crystal structure, phase purity and texture of the thin films, SEM/EDX will be used to study the local chemical composition and TEM for detailed examination of microstructure.   Measurement of electrical properties will be carried out with our collaborators at the University of Leeds. 

Also see homepages: Chris Grovenor Susannah Speller

Also see a full listing of New projects available within the Department of Materials.