Long minority carrier lifetime in Au-catalyzed GaAs/AlxGa1−xAs core-shell nanowires

GaAs/AlxGa1xAs core-shell nanowires were grown by metal organic chemical vapor deposition with optimized AlxGa1xAs shell and twin-free Au-catalyzed GaAs cores. Time-resolved photoluminescence measurements were carried out on single nanowires at room temperature, revealing minority carrier lifetimes of 1.02 6 0.43 ns, comparable to self-assisted nanowires grown by molecular beam epitaxy. The long minority carrier lifetimes are mainly attributed to improvement of the GaAs/AlxGa1xAs interface quality. The upper limit of surface recombination velocity of the structure is calculated to be 1300 cm/s with the AlxGa1xAs shell grown at 750 C, which is comparable with planar double heterostructures.The Australian Research Council is acknowledged for the financial support and the authors acknowledge the use of facilities in the Centre for Advanced Microscopy (AMMRF node) and the ACT node of the Australian National Fabrication Facility for this work

Autoimmune gastrointestinal complications in patients with Systemic Lupus Erythematosus: case series and literature review

The association of systemic lupus erythematosus (SLE) with gastrointestinal autoimmune diseases is rare, but has been described in the literature, mostly as case reports. However, some of these diseases may be very severe, thus a correct and early diagnosis with appropriate management are fundamental. We have analysed our data from the SLE patient cohort at University College Hospital London, established in 1978, identifying those patients with an associated autoimmune gastrointestinal disease. We have also undertaken a review of the literature describing the major autoimmune gastrointestinal pathologies which may be coincident with SLE, focusing on the incidence, clinical and laboratory (particularly antibody) findings, common aetiopathogenesis and complications

Droplet bulge effect on the formation of nanowire side facets

The process of lateral facet formation during vapor-liquid-solid nanowire growth is modeled to explain why the crystalline orientation of III-V nanowire side facets is affected by the droplet material. We find that the energy required for facet formatio

MOCVD growth of GaAs nanowires using Ga droplets

We report on growth of GaAs nanowires on Si(111) substrates using Ga droplets by metal-organic chemical vapour deposition (MOCVD). Appropriate growth conditions to achieve stabilization of small Ga droplets as well as Ga-assisted VLS growth of GaAs nanowires were found. This work facilitates comparative studies of crystalline quality and nanowire surfaces as a function of the droplet (catalyst) material

Distribution of zinc-blende twins and wurtzite segments in GaAs nanowires probed by X-ray nanodiffraction

We study by X-ray nanodiffraction the statistical distribution of the two possible twinned zinc-blende (ZB) orientations as well as the occurrence of the wurtzite structure within single GaAs nanowires (NWs) grown by molecular beam epitaxy on Si(111). A

Three-dimensional in situ photocurrent mapping for nanowire photovoltaics

Devices based upon semiconductor nanowires provide many well-known advantages for next-generation photovoltaics, however, limited experimental techniques exist to determine essential electrical parameters within these devices. We present a novel applicat

Twinning superlattice formation in GaAs nanowires

Semiconductor nanowires have proven a versatile platform for the realization of novel structures unachievable by traditional planar epitaxy techniques. Among these, the periodic arrangement of twin planes to form twinning superlattice structures has gene

Agrofibre reinforced poly(lactic acid) composites: Effect of moisture on degradation and mechanical properties

Natural fibre reinforced PLA composites are a 100% biobased material with a promising mechanical properties profile. However, natural fibres are hygroscopic whereas PLA is sensitive to hydrolytic degradation under melt processing conditions in the presence of small amounts of water. Here, we determine the effect of water content in undried and dried natural fibres on semi crystalline grade PLA degradation during processing as well as on the composite’s mechanical performance. The fibres evaluated are ramie, flax and cotton, containing 6–9 mass% moisture in the undried state and 0.2–0.4 mass% in the dried state. Intrinsic viscosity and melt flow index analysis indicate that the effect of the different levels of moisture in the fibres have a similar and small effect on PLA degradation, PLA hydrolysis appears rather affected by fibre diameter. Morphology, flexural strength and stiffness and Charpy impact of the composites are not significantly affected by the water present in the undried fibres

Growth and characterization of GaAx 1-x Sb x nanowires

We report the structural and optical characterization of GaAs 1-xSbx nanowires (NWs) grown on GaAs (111)B substrates using metalorganic chemical vapour deposition (MOCVD). The NWs are perpendicular to the substrate with almost defect-free zinc blende (ZB) structure. Micro-photoluminescence results demonstrate high emission efficiency at around 1.3 μm from the NWs

Improvement of Minority Carrier Lifetime in GaAs/Al x Gal 1-x As Core-Shell Nanowires

GaAs/AlxGa1-xAs core-shell nanowires were grown by metal organic chemical vapour deposition with Au-catalysed GaAs cores. Cross-section transmission electron microscope bright field images show that the tapering at bottom of the nanowires is mainly caused by GaAs cap growth. Time-resolved photo-luminescence measurements of single nanowires were taken at room temperature and a minority carrier lifetime of (1.02±0.43) ns was obtained for single nanowires with AlxGa1-xAs shell grown at 750°C. A close correlation between the shell growth temperature and minority carrier lifetime has also been observed