Enhanced oxidation stability of transparent copper films using a hybrid organic-inorganic nucleation layer

We report a novel seed layer for the formation of slab-like transparent copper films on glass and plastic substrates, based on a mixed molecular monolayer and an ultra-thin (0.8 nm) aluminium layer both deposited from the vapour phase, which substantially outperforms the best nucleation layer for optically thin copper films reported to date. Using this hybrid layer, the metal percolation threshold is reduced to < 4 nm nominal thickness and the long-term stability of sub-10 nm films towards oxidation in air is comparable to that of silver films of the same thickness fabricated using the best reported seed layer for optically thin silver films to date. The underlying reason for the remarkable effectiveness of this hybrid nucleation is elucidated using a combination of photoelectron spectroscopy, small angle X-ray studies, atomic force microscopy and transmission electron microscopy

Widely applicable coinage metal window electrodes on flexible polyester substrates applied to organic photovoltaics

The fabrication, exceptional properties, and application of 8 nm thick Cu, Ag, Au, and Cu/Ag bilayer electrodes on flexible polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates is reported. These electrodes are fabricated using a solvent free process in which the plastic surface is chemically modified with a molecular monolayer of thiol and amine terminated alkylsilanes prior to metal deposition. The resulting electrodes have a sheet resistance of ≤14 Ω sq–1, are exceptionally robust and can be rapidly thermally annealed at 200 °C to reduce their sheet resistance to ≤9 Ω sq–1. Notably, annealing Au electrodes briefly at 200 °C causes the surface to revert almost entirely to the {111} face, rendering it ideal as a model electrode for fundamental science and practical application alike. The power conversion efficiency of 1 cm2 organic photovoltaics (OPVs) employing 8 nm Ag and Au films as the hole-extracting window electrode exhibit performance comparable to those on indium–tin oxide, with the advantage that they are resistant to repeated bending through a small radius of curvature and are chemically well-defined. OPVs employing Cu and bilayer Cu:Ag electrodes exhibit inferior performance due to a lower open-circuit voltage and fill factor. Measurements of the interfacial energetics made using the Kelvin probe technique provide insight into the physical reason for this difference. The results show how coinage metal electrodes offer a viable alternative to ITO on flexible substrates for OPVs and highlight the challenges associated with the use of Cu as an electrode material in this contex

Charmonium properties from lattice QCD + QED: hyperfine splitting, J/ψJ/\psi leptonic width, charm quark mass and aμca_{\mu}^c

We have performed the first $n_f = 2+1+1$ lattice QCD computations of the properties (masses and decay constants) of ground-state charmonium mesons. Our calculation uses the HISQ action to generate quark-line connected two-point correlation functions on MILC gluon field configurations that include $u/d$ quark masses going down to the physical point, tuning the $c$ quark mass from $M_{J/\psi}$ and including the effect of the $c$ quark's electric charge through quenched QED. We obtain $M_{J/\psi}-M_{\eta_c}$ (connected) = 120.3(1.1) MeV and interpret the difference with experiment as the impact on $M_{\eta_c}$ of its decay to gluons, missing from the lattice calculation. This allows us to determine $\Delta M_{\eta_c}^{\mathrm{annihiln}}$ =+7.3(1.2) MeV, giving its value for the first time. Our result of $f_{J/\psi}=$ 0.4104(17) GeV, gives $\Gamma(J/\psi \rightarrow e^+e^-)$=5.637(49) keV, in agreement with, but now more accurate than experiment. At the same time we have improved the determination of the $c$ quark mass, including the impact of quenched QED to give $\overline{m}_c(3\,\mathrm{GeV})$ = 0.9841(51) GeV. We have also used the time-moments of the vector charmonium current-current correlators to improve the lattice QCD result for the $c$ quark HVP contribution to the anomalous magnetic moment of the muon. We obtain $a_{\mu}^c = 14.638(47) \times 10^{-10}$, which is 2.5$\sigma$ higher than the value derived using moments extracted from some sets of experimental data on $R(e^+e^- \rightarrow \mathrm{hadrons})$. This value for $a_{\mu}^c$ includes our determination of the effect of QED on this quantity, $\delta a_{\mu}^c = 0.0313(28) \times 10^{-10}$.Comment: Added extra discussion on QED setup, some new results to study the effects of strong isospin breaking in the sea (including new Fig. 1) and a fit stability plot for the hyperfine splitting (new Fig. 7). Version accepted for publication in PR

Site Condition Assessments of Welsh SAC and SSSI Standing Water Features

This report was commissioned by the Countryside Council for Wales (CCW) in 2005 and provides an assessment of the conservation status of Welsh Special Areas of Conservation (SACs) and Sites of Special Scientific Interest (SSSIs). It details the site condition assessments of 43 individual standing water features and provides overall assessments of the 13 SACs and 11 SSSIs in which they lie. Site condition is assessed using Common Standards Monitoring (CSM) methods, where specific habitat feature attributes are assessed against targets corresponding to ‘favourable’ condition. To make these assessments, data from CCW Contract Science Report no. 704 (Goldsmith et al. 2006) is employed, alongside further chemical and biological data collected by ENSIS Ltd. and the Environment Agency (EA) between 2003-2005. Data from previous reports and surveys is also utilised where available to provide a longer-term perspective and possible evidence of trends. The results of the site condition assessments are discussed in terms of general categories of impact (e.g. acidification or eutrophication). Where sites were in unfavourable condition, recommendations for further investigation and / or management are made. Reference is also made to Water Framework Directive (WFD) Risk Assessments and some attempt is made to relate condition assessment outcomes to the probability of sites failing to meet good ecological status by 2015 in accordance with the objectives of Article 4 of the WFD. Condition assessments for the oligotrophic to mesotrophic Welsh lake SACs (23 lakes) and SSSIs (7 lakes) with vegetation of the Littorelletea uniflorae and / or of the IsoëtoNanojuncetea, indicate that approximately 80 % of lakes of this type are currently in ‘unfavourable’ (60 %) or ‘unfavourable, recovering’ (20 %) condition. Only one SAC - Cadair Idris (3 lakes) – and three lakes within two other SACs are classified as ‘favourable’. Acidification is the primary reason for failure to meet favourable condition targets, particularly for SAC lakes. The recovery trends observed at a number of acid-impacted lakes most likely relate to reductions in atmospheric deposition of sulphur and nitrogen. It is expected that alkalinisation trends will continue provided that atmospheric deposition stabilises or continues to decrease. Nutrient enrichment, grazing pressure, sediment inwash, forestry operations and drawdown are further pressures that result in unfavourable condition assessment outcomes. Eutrophication is of particular concern amongst SSSI lakes of this type. All eleven Welsh lake SACs and SSSIs of the naturally eutrophic type (with Magnopotamion or Hydrocharition-type vegetation) or hard oligo-mesotrophic Chara spp. type are classified as ‘unfavourable’ (70 %) or ‘unfavourable, recovering’ (20 %), with one lake classified as ‘unfavourable, declining’. Eutrophication is the primary reason for failure to meet favourable condition targets. However, unlike acidification, eutrophication may come from both point and diffuse sources, and its effects may be exacerbated by local management practices such as grazing and fish stocking. For many eutrophied lakes there is scope to identify and reduce diffuse sources of nutrients within the catchment. However, residual sediment nutrient concentrations may be problematic, as may inappropriate fish communities resulting from past stocking practices. Eutrophication can dramatically alter the structure and function of a lake ecosystem; therefore carefully constructed management plans must be implemented if favourable condition is to be a realistic future target for impacted naturally eutrophic and hard-water Welsh lake SACs and SSSIs. Only one SAC in Wales is notified for the dystrophic lakes feature (2 lakes). This feature was provisionally classified as unfavourable. However, the targets for this habitat type may require refinement. The report concludes by discussing uncertainty in lake classification, data confidence concerns, CSM issues relating to survey methodology and the appropriateness of targets used for condition assessment. Comparisons between the CSM approach and other lake assessment methodologies are also considered. Overall recommendations for future monitoring and assessment are provided