Optical transmittance measurements on epitaxial, phase-pure, wurtzite-structure Sc x Ga 1-x N films with 0 ≤ x ≤ 0.26 showed that their direct optical band gaps increased from 3.33 eV to 3.89 eV with increasing x, in agreement with theory. These films contained I 1 -and I 2 -type stacking faults. However, the direct optical band gaps decreased from 3.37 eV to 3.26 eV for Sc x Ga 1-x N films which additionally contained nanoscale lamellar inclusions of the zincblende phase, as revealed by aberration-corrected scanning transmission electron microscopy. Therefore we conclude that the apparent reduction in Sc x Ga 1-x N band gaps with increasing x is an artefact resulting from the presence of nanoscale zinc-blende inclusions.

This paper establishes the potential of the recently introduced ABX3 metal-free perovskite structures for third-order nonlinear optical processes. The base unit in this family of materials is an ammonium halide octahedra, and it incorporates a large aromatic cation spacer forming the classic perovskite structure. This work shows that the choice of cation is key to the resulting third-order nonlinearity, where the incorporation of “MDABCO” into the structure, a very polar cation, results in a third-order nonlinear refractive index on the order of 10–17 m2 W–1 and high laser damage threshold of 0.8 J cm–2. Owing to its very wide band gap of ∼5.12 eV, this material exhibits a high nonlinear figure of merit across the visible and near-infrared transmission windows. These results show that the metal-free family of perovskite materials is an excellent candidate for nonlinear optics in the important visible and near-infrared wavelength regimes.

This is a repository copy of The effect of metal-rich growth conditions on the microstructure of ScxGa1-xN films grown using molecular beam epitaxy.White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/93558/ Version: Accepted Version Article:Tsui, H.C.L., Goff, L.E., Barradas, N.P. et al. (7 more authors) (2015) The effect of metal-rich growth conditions on the microstructure of ScxGa1-xN films grown using molecular beam epitaxy. physica status solidi (a), 212 (12). 2837 -2842. ISSN 1862-6300 https://doi.org/10.1002/pssa.201532292 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. AbstractEpitaxial ScxGa1-xN films with 0 x 0.50 were grown using molecular beam epitaxy under metal-rich conditions. The ScxGa1-xN growth rate increased with increasing Sc flux despite the use of metal-rich growth conditions, which is attributed to the catalytic decomposition of N2 induced by the presence of Sc. Microstructural analysis showed that phase-pure wurtzite ScxGa1-xN was achieved up to x = 0.26, which is significantly higher than that previously reported for nitrogen-rich conditions, indicating that the use of metalrich conditions can help to stabilise wurtzite phase ScxGa1-xN.Keywords: ScGaN, molecular beam epitaxy, TEM PACS codes: 61.66Dk, 68.55Nq, 81.05Ea, 81.15Hi 1 Introduction Wurtzite-structure III-nitrides are of interest for optoelectronic and high power electronic applications. These semiconductors include AlN, GaN and InN and their alloys, which have direct band gaps of 6.2 eV, 3.4 eV and 0.7 eV respectively [1][2][3][4] and are therefore able to emit light across the ultraviolet, violet and red spectral regions. However, current state-of-the-art optoelectronic devices suffer from poor internal quantum efficiencies, partly due to the lattice mismatch with the substrate or between layers leading to high dislocation densities and in-plane stresses [5]. Therefore, it is of interest to develop new wurtzite-structure nitride semiconductors with different lattice parameter-band gap relationships, such as alloys between GaN and ScN.

Semiconductor optoelectronic fiber technology has seen rapid development in recent years thanks to advancements in fabrication and post-processing techniques. Integrating the optical and electronic functionality of semiconductor materials into a fiber geometry has opened up many possibilities, such as in-fiber frequency generation, signal modulation, photodetection, and solar energy harvesting. This review provides an overview of the state-of-the-art in semiconductor optoelectronic fibers, including fabrication and post-processing methods, materials and their optical properties. The applications in nonlinear optics, optical-electrical conversion, lasers and multimaterial functional fibers will also be highlighted.

the optical response of a graphene oxide integrated silicon micro-ring resonator (GoMRR) to a range of vapour phase Volatile organic compounds (Vocs) is reported. the response of the GoMRR to all but one (hexane) of the VOCs tested is significantly higher than that of the uncoated (control) silicon MRR, for the same vapour flow rate. An iterative Finite Difference Eigenmode (FDE) simulation reveals that the sensitivity of the GO integrated device (in terms of RIU/nm) is enhanced by a factor of ~2, which is coupled with a lower limit of detection. critically, the simulations reveal that the strength of the optical response is determined by molecular specific changes in the local refractive index probed by the evanescent field of the guided optical mode in the device. Analytical modelling of the experimental data, based on Hill-Langmuir adsorption characteristics, suggests that these changes in the local refractive index are determined by the degree of molecular cooperativity, which is enhanced for molecules with a polarity that is high, relative to their kinetic diameter. We believe this reflects a molecular dependent capillary condensation within the graphene oxide interlayers, which, when combined with highly sensitive optical detection, provides a potential route for discriminating between different vapour phase VOCs.