High quality GaMnAs films grown with As dimers

We demonstrate that GaMnAs films grown with As2 have excellent structural, electrical and magnetic properties, comparable or better than similar films grown with As4. Using As2, a Curie temperature of 112K has been achieved, which is slightly higher than the best reported to date. More significantly, films showing metallic conduction have been obtained over a much wider range of Mn concentrations (from 1.5% to 8%) than has been reported for films grown with As4. The improved properties of the films grown with As2 are related to the lower concentration of antisite defects at the low growth temperatures employed.Comment: 8 pages, accepted for publication in J. Crystal Growt

Reorienting finance towards energy efficiency: the case of UK housing

This paper examines the challenges associated with stimulating large-scale investment in energy efficiency and demand management measures, using residential energy efficiency improving retrofits in the UK as a case study. We consider how issues of energy policy, consumer choice and financial systems intersect, drawing on recent literature including energy policy documents and research reports, and on interviews with stakeholders from the finance sector, energy efficiency practitioners and more. We suggest that following the withdrawal of the Green Deal, there is a need to reconsider the framing of policy for household energy efficiency improvements, and examine three potential aspects of a new framing: energy efficiency as infrastructure; new business and financing models for energy efficiency provision; and decentralised financing institutions for energy efficiency investment. This would require a long-term commitment from government on energy efficiency, and a need to ensure that projects are attractive and investable from both householders and investors’ perspectives. We conclude that there are important roles for government in any large scale initiative for energy efficient retrofitting of UK homes, even if the mechanisms are market based. These includes signalling long-term policy consistency and reducing risks for financial investment, and intermediating between finance and energy efficiency projects

Anisotropic excitation spectra of GaAs/AlGaAs quantum wells grown on vicinal plane substrates

We report measurements of the photoluminescence excitation spectra of a series of GaAs/AlGaAs quantum well samples grown on vicinal plane substrates with differing off‐cut angles. When the plane of polarization of the exciting light is changed we have observed a clear variation in the ratio of the strength of the n=1 light and heavy hole exciton transitions in samples grown on vicinal plane substrates. This behavior is attributed to anisotropic scattering at steps in the heterointerface

The United Kingdom smart meter rollout through an energy justice lens

The United Kingdom’s Smart Meter Implementation Programme (SMIP) creates the legal framework so that an in-home display unit and a smart gas and electricity meter can be installed in every household by the end of 2020. Intended to reduce household energy consumption, the SMIP is one of the world’s most complex smart meter rollouts. It is also proving to be a challenging one as a series of obstacles has characterised and potentially restricted implementation. This chapter first gives background to the most recent smart meter roll out developments in the UK and second, uses an energy justice framework to explore the emergent challenges under the titles of distributional justice, procedural justice and justice as recognition. Applying this framework to an analysis of the UK SMIP provides opportunities to accurately record, present and expose potential forthcoming injustices. In light of this, we offer a series of policy recommendations

Two-Dimensional, Pyrazine-Based Nonlinear Optical Chromophores with Ruthenium(II) Ammine Electron Donors

Six new nonlinear optical (NLO) chromophores with pyrazinyl-pyridinium electron acceptors have been synthesized by complexing a known pro-ligand with electron donating {Ru^(II)(NH_3)_5}^(2+) or trans-{Ru^(II)(NH_3)_4(py)}^(2+) (py = pyridine) centers. These cationic complexes have been characterized as their PF_6^− salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. The visible d → π* metal-to-ligand charge-transfer (MLCT) absorptions gain intensity on increasing the number of Ru^(II) centers from one to two, but remain at constant energy. One or two Ru^(III/II) redox processes are observed which are reversible, quasi-reversible, or irreversible, while all of the ligand-based reductions are irreversible. Molecular first hyperpolarizabilities β have been determined by using hyper-Rayleigh scattering (HRS) at 1064 nm, and depolarization studies show that the NLO responses of the symmetric species are strongly two-dimensional (2D) in character, with dominant “off-diagonal” β_(zyy) components. Stark (electroabsorption) spectroscopic measurements on the MLCT bands also allow the indirect determination of estimated static first hyperpolarizabilities β_0. Both the HRS and the Stark-derived β_0 values increase on moving from mono- to bimetallic complexes, and substantial enhancements in NLO response are achieved when compared with one-dimensional (1D) and 2D monometallic Ru^(II) ammine complexes reported previously