Zeeman splittings of the 5D0–7F2 transitions of Eu3+ ions implanted into GaN

We report the magnetic field splittings of emission lines assigned to the 5D0–7F2 transitions of Eu3+ centres in GaN. The application of a magnetic field in the c-axis direction (B||c) leads to a splitting of the major lines at 621 nm, 622 nm and 622.8 nm into two components. The Zeeman splitting is linear with magnetic field up to 5 Tesla for each line. In contrast, a magnetic field applied in the growth plane (B┴c) does not influence the photoluminescence spectra. The estimated g-factors vary slightly from sample to sample with mean values of g|| ~2.8, ~1.5 and ~2.0 for the emission lines at 621 nm, 622 nm and 622.8 nm respectively

The origin of the red luminescence in Mg-doped GaN

Optically-detected magnetic resonance (ODMR) and positron annihilation spectroscopy (PAS) experiments have been employed to study magnesium-doped GaN layers grown by metal-organic vapor phase epitaxy. As the Mg doping level is changed, the combined experiments reveal a strong correlation between the vacancy concentrations and the intensity of the red photoluminescence band at 1.8 eV. The analysis provides strong evidence that the emission is due to recombination in which electrons both from effective mass donors and from deeper donors recombine with deep centers, the deep centers being vacancy-related defects.Comment: 4 pages, 3 figure

Optical energies of AllnN epilayers

Optical energy gaps are measured for high-quality Al1−xInxN-on-GaN epilayers with a range of compositions around the lattice match point using photoluminescence and photoluminescence excitation spectroscopy. These data are combined with structural data to determine the compositional dependence of emission and absorption energies. The trend indicates a very large bowing parameter of 6 eV and differences with earlier reports are discussed. Very large Stokes' shifts of 0.4-0.8 eV are observed in the composition range 0.13<x<0.24, increasing approximately linearly with InN fraction despite the change of sign of the piezoelectric fiel

Comparison of Zn_{1-x}Mn_xTe/ZnTe multiple-quantum wells and quantum dots by below-bandgap photomodulated reflectivity

Large-area high density patterns of quantum dots with a diameter of 200 nm have been prepared from a series of four Zn_{0.93}Mn_{0.07}Te/ZnTe multiple quantum well structures of different well width (4 nm, 6 nm, 8 nm and 10 nm) by electron beam lithography followed by Ar+ ion beam etching. Below-bandgap photomodulated reflectivity spectra of the quantum dot samples and the parent heterostructures were then recorded at 10 K and the spectra were fitted to extract the linewidths and the energy positions of the excitonic transitions in each sample. The fitted results are compared to calculations of the transition energies in which the different strain states in the samples are taken into account. We show that the main effect of the nanofabrication process is a change in the strain state of the quantum dot samples compared to the parent heterostructures. The quantum dot pillars turn out to be freestanding, whereas the heterostructures are in a good approximation strained to the ZnTe lattice constant. The lateral size of the dots is such that extra confinement effects are not expected or observed.Comment: 23 pages, LaTeX2e (amsmath, epsfig), 7 EPS figure

Naming and Framing the Behavioural and Psychological Symptoms of Dementia (BPSD) Paradigm: Professional Stakeholder Perspectives

Background: Behavioural and Psychological Symptoms of Dementia and Challenging Behaviour in dementia are just two of a variety of terms for a complex paradigm that covers the most distressing and costly aspects of the condition. The terminology used to describe these aspects can influence what is measured as outcomes and what is considered as evidence of improvement. Unhelpful or outmoded narratives could be a barrier to developing innovative interventions or in determining what works for whom. This UK study explored professional opinions about commonly used terminology in this paradigm. Methods: This mixed methods study involved wide-ranging multidisciplinary professionals and stakeholders. A consultation event was attended by 74 multidisciplinary professionals. Written feedback from this event was used to develop an online survey. The survey was disseminated using a cascading snowballing method through multi-professional groups. Survey respondents ranked preferences for terms and stated reasons for their choices. Thematic content analysis was used to explore patterns of meaning. Results: From the consultation event a list of 14 common terms were generated and formed the basis of the on-line survey. 378 respondents completed the survey. There was a wide variation across professional groups on preferred terminology with 'unmet need', 'behaviour that challenges', 'BPSD' and 'stress and distress' being ranked as the first choice by the majority. Five themes emerged from the qualitative data, revealing important nuances and challenges in relation to terminology. Conclusions: Words have the power to shape thoughts, beliefs, emotions and behaviour. In line with the international advocacy movement, our UK findings suggest that future international consensus should, in addition to multi-professional and stakeholder experts, involve wide-ranging groups of people with dementia, their families and advocates. This would ensure that we use descriptive language, that does not objectify peoples' experience and that can be easily understood by all

Linear polarization of the photoluminescence of quantum wells

The degree and orientation of the magnetic-field induced linear polarization of the photoluminescence from a wide range of heterostructures containing (Cd,Mn)Te quantum wells between (Cd,Mn,Mg)Te barriers has been studied as a function of detection photon energy, applied magnetic field strength and orientation in the quantum well plane. A theoretical description of this effect in terms of an in-plane deformation acting on the valence band states is presented and is verified by comparison with the experimental data. We attempted to identify clues to the microscopic origin of the valence band spin anisotropy and to the mechanisms which actually determine the linear polarization of the PL in the quantum wells subject to the in-plane magnetic field. The conclusions of the present paper apply in full measure to non-magnetic QWs as well as ensembles of disk-like QDs with shape and/or strain anisotropy.Comment: 21 pages, 10 figure

Are nurse's needs assessment methods robust enough to recognise palliative care needs in people with dementia? : a scoping review

People with dementia are most at risk of experiencing serious health related suffering, if they do not have a palliative care approach introduced early enough in the illness. It can be challenging for nurses to assess experienced needs of people, who are thought no longer able to self-report such as people with dementia. Assessment help to understand the care the patient and their family need promptly. It is unknown how nurses recognise holistic palliative care needs in people with dementia during routine care