http://hdl.handle.net/2173/31595 Thu, 23 May 2013 12:37:11 GMT 2013-05-23T12:37:11Z http://hdl.handle.net/2173/110926 Title: Advances in the use of MOCVD methods for the production of novel photonic bandgap materials Authors: Whitehead, Debra; Pemble, Martyn; Yates, Heather; Blanco, A.; Lopez, C.; Miguez, H.; Meseguer, F. J. Abstract: We describe the use of novel MOCVD methods designed to infill templated structures based upon synthetic opals in order to provide increased refractive index contrast necessary for the creation of full photonic bandgap materials. The method employed is illustrated by considering the production of structures containing III-V material GaP and using this example, we demonstrate the ability to achieve levels of infill higher than any previously reported. We describe the use of novel MOCVD chemistry in the creation of a potentially new class of inorganic material, potentially capable of direct luminescence from within the photonic bandgap system. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Journal de Physique IV, published by and copyright EDP Sciences. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/2173/110926 2001-01-01T00:00:00Z http://hdl.handle.net/2173/110760 Title: Enhanced Bragg reflections from size-matched heterostructure photonic crystal thin films prepared by the Langmuir-Blodgett method Authors: Bardosova, M.; Pemble, Martyn; Povey, I. M.; Tredgold, R. H.; Whitehead, Debra Abstract: The Langmuir-Blodgett method was used to engineer photonic crystal thin films of an AB architecture. Structures were studied by transmittance and reflectance spectroscopies. For an AB structure in which the silica particle diameter B is twice that of A, reflectance features associated with the first order Bragg peak for the “A” domain are only observed when the structure is probed from the A side of the structure. Furthermore, this feature is enhanced in intensity compared to that for a structure consisting solely of A particles. These findings are attributed to a matching of first and second order Bragg processes. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Applied Physics Letters, published by and copyright American Institute of Physics. Mon, 28 Aug 2006 00:00:00 GMT http://hdl.handle.net/2173/110760 2006-08-28T00:00:00Z http://hdl.handle.net/2173/110759 Title: Transition states and rearrangement mechanisms from hybrid eigenvector-following and density functional theory. Application to C10H10 and defect migration in crystalline silicon Authors: Kumeda, Yuko; Munro, Lindsey; Wales, David J. Abstract: Hybrid eigenvector-following (EF) using variational eigenvector refinement and tangent space minimisation are combined with plane-wave density-functional calculations to characterise rearrangements of C10H10 and a variety of defect migration processes in crystalline silicon. For silicon we compare local and ‘non-local' density functionals and supercells containing 64±1 and 216±1 atoms. Changes in the supercell size and the density functional can produce significant changes in the mechanisms. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Chemical Physics Letters, published by and copyright Elsevier. Fri, 01 Jun 2001 00:00:00 GMT http://hdl.handle.net/2173/110759 2001-06-01T00:00:00Z http://hdl.handle.net/2173/110788 Title: Photonic crystal thin films of GaAs prepared by atomic layer deposition Authors: Povey, I. M.; Whitehead, Debra; Thomas, K.; Pemble, Martyn; Bardosova, M.; Renard, J. Abstract: Photonic crystal thin films were fabricated via the self-assembly of a lattice of silica spheres on silicon (100) substrates. Progressive infilling of the air spaces within the structure with GaAs was achieved using trimethylgallium and arsine under atomic-layer-deposition conditions. Samples with the highest levels of GaAs infill were subsequently inverted using selective etching. Reflectance spectra are interpreted via the Bragg expression and calculated photonic band structure diagrams. For GaAs infilled and inverted samples, the relative positions of the first and second order Bragg reflections are strongly influenced by the wavelength dependent refractive index. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Applied Physics Letters, published by and copyright American Institute of Physics. Fri, 01 Sep 2006 00:00:00 GMT http://hdl.handle.net/2173/110788 2006-09-01T00:00:00Z