Enhanced Bragg reflections from size-matched heterostructure photonic crystal thin films prepared by the Langmuir-Blodgett method

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

Photonic crystal thin films of GaAs prepared by atomic layer deposition

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

Determinants of adults' intention to vaccinate against pandemic swine flu

This article has been made available through the Brunel Open Access Publishing Fund.This article has been made available through the Brunel Open Access Publishing Fund.Background: Vaccination is one of the cornerstones of controlling an influenza pandemic. To optimise vaccination rates in the general population, ways of identifying determinants that influence decisions to have or not to have a vaccination need to be understood. Therefore, this study aimed to predict intention to have a swine influenza vaccination in an adult population in the UK. An extension of the Theory of Planned Behaviour provided the theoretical framework for the study. Methods: Three hundred and sixty two adults from the UK, who were not in vaccination priority groups, completed either an online (n = 306) or pen and paper (n = 56) questionnaire. Data were collected from 30th October 2009, just after swine flu vaccination became available in the UK, and concluded on 31st December 2009. The main outcome of interest was future swine flu vaccination intentions. Results: The extended Theory of Planned Behaviour predicted 60% of adults’ intention to have a swine flu vaccination with attitude, subjective norm, perceived control, anticipating feelings of regret (the impact of missing a vaccination opportunity), intention to have a seasonal vaccine this year, one perceived barrier: “I cannot be bothered to get a swine flu vaccination” and two perceived benefits: “vaccination decreases my chance of getting swine flu or its complications” and “if I get vaccinated for swine flu, I will decrease the frequency of having to consult my doctor,” being significant predictors of intention. Black British were less likely to intend to have a vaccination compared to Asian or White respondents. Conclusions: Theoretical frameworks which identify determinants that influence decisions to have a pandemic influenza vaccination are useful. The implications of this research are discussed with a view to maximising any future pandemic influenza vaccination uptake using theoretically-driven applications.This article is available through the Brunel Open Access Publishing Fund

Nephrocalcinosis (enamel renal syndrome) caused by autosomal recessive FAM20A mutations

Calcium homeostasis requires regulated cellular and interstitial systems interacting to modulate the activity and movement of this ion. Disruption of these systems in the kidney results in nephrocalcinosis and nephrolithiasis, important medical problems whose pathogenesis is incompletely understood

Atomic layer deposited electron transport Layers in efficient organometallic halide perovskite devices

Amorphous TiO2 and SnO2 electron transport layers (ETLs) were deposited by low-temperature atomic layer deposition (ALD). Surface morphology and x-ray photoelectron spectroscopy (XPS) indicate uniform and pinhole free coverage of these ALD hole blocking layers. Both mesoporous and planar perovskite solar cells were fabricated based on these thin films with aperture areas of 1.04 cm2 for TiO2 and 0.09 cm2 and 0.70 cm2 for SnO2. The resulting cell performance of 18.3 % power conversion efficiency (PCE) using planar SnO2 on 0.09 cm2 and 15.3 % PCE using mesoporous TiO2 on 1.04 cm2 active areas are discussed in conjunction with the significance of growth parameters and ETL composition

Band offsets and trap-related electron transitions at interfaces of (100)InAs with atomic-layer deposited Al2O3

Spectral analysis of optically excited currents in single-crystal (100)InAs/amorphous (a-)Al2O3/ metal structures allows one to separate contributions stemming from the internal photoemission (IPE) of electrons into alumina and from the trapping-related displacement currents. IPE spectra suggest that the out-diffusion of In and, possibly, its incorporation in a-Al2O3 lead to the development of 0.4 eV wide conduction band (CB) tail states. The top of the InAs valence band is found at 3.4560.10 eV below the alumina CB bottom, i.e., at the same energy as at the GaAs/a-Al2O3 interface. This corresponds to the CB and the valence band offsets at the InAs/a-Al2O3 interface of 3.160.1 eV and 2.560.1 eV, respectively. However, atomic-layer deposition of alumina on InAs results in additional low-energy electron transitions with spectral thresholds in the range of 2.0–2.2 eV, which is close to the bandgap of AlAs. The latter suggests the interaction of As with Al, leading to an interlayer containing Al-As bonds providing a lower barrier for electron injection.received: 2016-09-05 accepted: 2016-11-17 published: 2016-12-15status: publishe

Hall-effect mobility for a selection of natural and synthetic 2D semiconductor crystals

We present a DC-AC Hall-effect analysis on transition-metal-dichalcogenides comprising natural crystals of molybdenum disulfide and tungsten diselenide; and synthetic crystals of hafnium diselenide, molybdenum ditelluride, molybdenum diselenide and niobium-doped molybdenum disulfide. We observe a wide range of Hall mobility and carrier concentration values with either a net electron or hole carrier type. The synthetic niobium-doped molybdenum disulfide crystal exhibits a net hole carrier type and a carrier concentration approximately two orders of magnitude higher than a non-intentionally doped natural molybdenum disulfide crystal, with an equivalent reduction in Hall mobility. This synthetic niobium-doped molybdenum disulfide crystal also shows a significantly reduced resistivity when compared to the other crystals. Secondary ion mass spectrometry shows higher counts of niobium in the intentionally-doped synthetic niobium-molybdenum disulfide crystal, in addition to various other high contamination counts in both the natural and synthetic molybdenum disulfide crystals, correlating well with the significant range of high resistivity observed. Compared to silicon, the resistivity in these contaminated TMD materials reduces less rapidly with increasing equivalent carrier concentration levels, and the resistivity is higher in magnitude by a factor of approximately 4-10 when compared to silicon, which in turn reduces the achievable Hall mobility by at least a similar factor. It is therefore suggested that more controlled growth methods of TMD materials which lead to significantly reduced contamination elements and levels, with improved stoichiometry, could potentially provide a significant increase in Hall mobility assuming no change in carrier properties