1,537 research outputs found
Multiple wavelength InGaAs quantum dot lasers using selective area epitaxy
The authors demonstrate multiple wavelength lasers fabricated from InGaAsquantum dots. Selective area epitaxy is used to grow the active region, consisting of five layer stack of InGaAsquantum dots with different band gapenergies in selected regions of the substrate, for fabrication of the lasers. The mechanism responsible for engineering of the band gap of quantum dots is discussed. The performance of the selectively grown lasers is compared to the lasers fabricated from structures grown in a standard, nonselective area growth process.The Australian Research Council is gratefully acknowledged
for financial support
Spatially resolved characterization of InGaAs/GaAs quantum dot structures by scanning spreading resistance microscopy
Cross-sectional scanning spreading resistance microscopy (SSRM) is used to investigate stacked InGaAs/GaAs quantum dot(QD)structures with different doping schemes. Spatially resolved imaging of the QDs by SSRM is demonstrated. The SSRM contrast obtained for the QD layers is found to depend on doping in the structure. In the undoped structures both QD-layers and QDs within the layers could be resolved, while in the dopedstructures the QD layers appear more or less uniformly broadened. The origin of the SSRM contrast in the QD layer in the different samples is discussed and correlated with doping schemes.T. Hakkarainen, O. Douhéret, and S. Anand would like
to acknowledge the Swedish Research Council VR for fi-
nancial support and the Kurt-Alice Wallenberg KAW foundation
for financing the microscope. L. Fu, H. H. Tan, and C.
Jagadish would like to acknowledge the Australian Research
Council ARC for financial support and Australian National
Fabrication Facility ANFF for access to the facilities
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Comparing proxy rated quality of life of people living with dementia in care homes
Background: Improving quality of life (QOL) for people with dementia is a priority. In care homes, we often rely on proxy ratings from staff and family but we do not know if, or how, they differ in care homes.
Methods: We compared 1056 pairs of staff and family DEMQOL-Proxy ratings from 86 care homes across England. We explored factors associated with ratings quantitatively using multilevel modelling and, qualitatively, through thematic analysis of 12 staff and 12 relative interviews.
Results: Staff and family ratings were weakly correlated (ρs = 0.35). Median staff scores were higher than family's (104 v. 101; p < 0.001). Family were more likely than staff to rate resident QOL as ‘Poor’ (χ2 = 55.91, p < 0.001). Staff and family rated QOL higher when residents had fewer neuropsychiatric symptoms and severe dementia. Staff rated QOL higher in homes with lower staff:resident ratios and when staff were native English speakers. Family rated QOL higher when the resident had spent longer living in the care home and was a native English. Spouses rated residents’ QOL higher than other relatives. Qualitative results suggest differences arise because staff felt good care provided high QOL but families compared the present to the past. Family judgements centre on loss and are complicated by decisions about care home placement and their understandings of dementia.
Conclusion: Proxy reports differ systematically between staff and family. Reports are influenced by the rater:staff and family may conceptualise QOL differently
High temperature rapid thermal annealing of phosphorous ion implanted InAs∕InP quantum dots
The effect of high temperature annealing of the InAs∕InPquantum dots(QDs) containing a thin GaAs interlayer is investigated. The QDs are rapid thermally annealed at 750, 800, 850, and 900°C for 30s. The QDs with the GaAs interlayer show good thermal stability up to 850°C as well as enhanced integrated photoluminescence (PL) intensity and reduced PL linewidth. The effect of high energy(450keV) phosphorous ion implantation at room temperature with doses of 5×10¹¹–5×10¹³ions/cm² with subsequent high temperature (750–850°C)rapid thermal annealing is also studied. A large implantation-inducedenergy shift of up to 309meV (400nm) is observed. The implanted samples annealed at 850°C show reduced PL linewidth and enhanced integrated PL intensity compared to the implanted samples annealed at 750°C.The authors gratefully acknowledge financial support
from the Australian Research Council
Proton implantation-induced intermixing of InAs∕InP quantum dots
Protonimplantation-induced intermixing of InAsquantum dots(QDs) capped with InP, GaInAsP, and InP and InGaAs layers grown by metal-organic chemical vapor deposition is investigated. The samples are annealed at 750, 800, 850, and 900°C for 30s and thermal stability of the QDs is studied. The optimum annealing temperature is around 800°C which gives maximum implantation-induced energy shift. The QDs capped with InP layers show the highest implantation-induced energy shift due to strong group V interdiffusion whereas the QDsgrown on and capped with GaInAsP layers show the least implantation-induced energy shift due to weak group V and group III interdiffusion. The QDs capped with InP and InGaAs layers show intermediate implantation-induced energy shift and are less thermally stable compared to the QDsgrown on and capped with GaInAsP layers. The QDs capped with InP layers show enhanced photoluminescence(PL) intensity when implanted with lower proton dose (less than 5×10¹⁴ions/cm²). On the other hand higher proton dose (more than 1×10¹⁴ions/cm²) reduces the PL linewidth in all samples.The authors gratefully acknowledge financial support
from the Australian Research Council
Impurity-free disordering of InAs/InP quantum dots
Impurity-free disordering (IFD) of the InAs quantum dots (QDs) capped with either an InP layer or an InGaAs∕InP bilayer is studied. The samples are coated with a SiO₂ or TiO₂ dielectric layer followed by rapid thermal annealing at 700, 750, 800, and 850°C for 30s . A large differential energy shift of 157meV is induced by SiO₂ in the QDs capped with an InGaAs∕InP bilayer. Contrary to the reported results on the suppression of intermixing of GaAs based QDs by TiO₂ , the authors find that intermixing of InAs∕InP QDs is promoted by TiO2 . X-ray photoelectron spectroscopy depth profiles show that both In and P outdiffuse to a TiO₂ layer whereas Ga, In, and P outdiffuse to a SiO₂ layer leading to different degrees of intermixing. The results indicate that a group V interstitial diffusion mechanism might be responsible for IFD of InAs∕InP QDs.The financial
support from the Australian Research Council is also gratefully
acknowledged
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Persistent barriers and facilitators to seeking help for a dementia diagnosis: a systematic review of 30 years of the perspectives of carers and people with dementia
Objective:
To identify barriers and facilitators to help seeking for a dementia diagnosis from the perspective of carers and people with dementia.
Design:
A systematic review of the literature was conducted according to the PRISMA guidelines (PROSPERO protocol registration CRD42018092524). Nine electronic databases were searched for qualitative, quantitative, and mixed methods primary research studies. Two independent reviewers screened titles and abstracts, full texts of eligible studies, and conducted quality appraisal of included articles. A convergent qualitative synthesis approach was used.
Results:
From 7496 articles, 35 papers representing 32 studies from 1986 to 2017 were included. Studies originated from 13 countries across 4 continents. Barriers and facilitators were reported predominantly by carers. A small number of studies included people with dementia. Barriers included denial, stigma and fear, lack of knowledge, normalization of symptoms, preserving autonomy, lack of perceived need, unaware of changes, lack of informal network support, carer difficulties, and problems accessing help. Facilitators included recognition of symptoms as a problem, prior knowledge and contacts, and support from informal network.
Conclusions:
Studies from a 30-year period demonstrated that barriers to help seeking persist globally, despite increasing numbers of national dementia policies. Barriers and facilitators rarely existed independently demonstrating the complexity of help seeking for a diagnosis of dementia. Multiple barriers compounded the decision-making process and more than one facilitator was often required to overcome them. Multi-faceted interventions to reduce barriers are needed, one approach would be a focus on the development of dementia friendly communities to reduce stigma and empower people with dementia and carers
Temperature dependent photoluminescence in oxygen ion implanted and rapid thermally annealed ZnO/ZnMgO multiple quantum wells
The authors investigate the effect of oxygen implantation and rapid thermal annealing in ZnO∕ZnMgOmultiple quantum wells using photoluminescence. A blueshift in the photoluminescence is observed in the implanted samples. For a low implantation dose, a significant increase of activation energy and a slight increase of the photoluminescence efficiency are observed. This is attributed to the suppression of the point defect complexes and transformation between defect structures by implantation and subsequent rapid thermal annealing. A high dose of implantation leads to lattice damage and agglomeration of defects leading to large defect clusters, which result to an increase in nonradiative recombination.The authors gratefully acknowledge the Australian Research
Council for financial support and Swinburne University
of Technology for Strategic Initiative funding. One of
the authors X.W. acknowledges partial financial support of
the Chinese National Natural Science Foundation
10364004 and the Yunnan Natural Science Foundation
2003E0013M
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