High Temperature Annealing (high + temperature_annealing)

Distribution by Scientific Domains


Selected Abstracts


Thermal activation of beryllium-related photoluminescence by annealing of GaN grown by molecular beam epitaxy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
Kyoungnae Lee
Abstract Surface polarity related differences in the optical activity of Be in GaN epilayers grown by rf-plasma molecular beam epitaxy are investigated. N-polar GaN doped with Be exhibits a significantly higher intensity of donor-acceptor pair (DAP) photoluminescence (PL) than similarly doped Ga-polar GaN, indicating the Be is incorporating at microscopically different sites, or possibly is forming different compensating complexes. Highly Be-doped Ga-polar GaN forms isolated polarity-inverted regions which then incorporate Be via the N-polar mechanism resulting in the DAP PL. High temperature annealing of the Ga-polar layers both under nitrogen/hydrogen mixtures and under pure nitrogen atmospheres activates the DAP PL. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


A Transparent, Flexible, Low-Temperature, and Solution-Processible Graphene Composite Electrode

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Haixin Chang
Abstract The synthesis and preparation of a new type of graphene composite material suitable for spin-coating into conductive, transparent, and flexible thin film electrodes in ambient conditions is reported here for the first time. Solution-processible graphene with diameter up to 50 ,m is synthesized by surfactant-assisted exfoliation of graphite oxide and in situ chemical reduction in a large quantity. Spin-coating the mixing solution of surfactant-functionalized graphene and PEDOT:PSS yields the graphene composite electrode (GCE) without the need for high temperature annealing, chemical vapor deposition, or any additional transfer-printing process. The conductivity and transparency of GCE are at the same level as those of an indium tin oxide (ITO) electrode. Importantly, it exhibits high stability (both mechanical and electrical) in bending tests of at least 1000 cycles. The performance of organic light-emitting diodes based on a GCE anode is comparable, if not superior, to that of OLEDs made with an ITO anode. [source]


Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymer

MACROMOLECULAR SYMPOSIA, Issue 1 2003
Francesco Paolo La Mantia
Abstract Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrillation is increased, especially for the blends with the higher molar mass LDPE grade. The mechanical properties of the latter blends were found to be considerably enhanced by the addition of EAA, whereas the improvement was relatively modest for the blends with the lower molar mass LDPE. The fracture properties of double end notched samples of the ribbons prepared with the blends containing the lower molar mass LDPE grade were also studied. It was shown that, despite of the increased interfacial adhesion caused by the presence of EAA, the latter plays a measurable positive effect on the fracture properties only for the blends with LDPE as the matrix. [source]


Interdiffusion in SiGe alloys with Ge contents of 25% and 50% studied by X-ray reflectivity

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008
M. Medun
Abstract The interdiffusion in SiGe alloys has been studied by X-ray specular reflectivity using ex-situ and in-situ annealing experiments. We report on the evolution of the Ge profile of strain-compensated Si/SiGe multilayers due to high temperature annealing. These multilayers were grown pseudomorphically and strain-symmetrized on relaxed Si0.75Ge0.25 and Si0.5Ge0.5 pseudosubstrates by molecular beam epitaxy at 330 C. The multilayer structures were annealed at several temperatures around 590 C and around 800 C. From modelling the X-ray specular reflectivity scans at various stages of the interdiffused structures, we obtained interdiffusion coefficients resulting in the activation energy and the prefactor for interdiffusion corresponding to Si0.75Ge0.25 and Si0.5Ge0.5. The results obtained ex-situ for Si0.5Ge0.5 and in-situ for Si0.75Ge0.25 provide accurate values of diffusion parameters. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Investigation of ZnO substrates: effects of high temperature annealing

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
S. Graubner
Abstract In order to promote growth of ZnO films on ZnO substrates, defects introduced by the surface polishing procedure have to be removed. We investigate the influence of high temperature annealing in O2 -atmosphere on the structural properties of the ZnO substrates by atomic force microscopy. Only at temperatures above 1100 C atomic steps (terraces) are seen, the remaining defects can be assigned to dislocations in a density between 104 to 105 cm,2. Interestingly the electrical properties also change from high resistive to n-type conduction, which make the substrates , apart for the homoepitaxial growth on a perfect template , suitable for top-to-bottom contacts. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Formation of ohmic contacts to ultra-thin channel AlN/GaN HEMTs

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
Tom Zimmermann
Abstract AlN/GaN-based high electron mobility transistors with ultra-thin AlN barriers of 2.3 - 5 nm are attractive candidates for very high speed applications owing to the aggressive scalability such structures afford. We report the first study on formation of ohmic contacts to these high quality ultra-thin channel heterostructures (ns > 1x1013 cm,2 and , > 900 cm2/Vs) with systematically varying barrier thicknesses. While the conventional ohmic contacts to AlGaN/GaN structures generally require high temperature annealing, these ohmic contacts were found to behave ohmic or near ohmic as-deposited. Annealing (400-860 0C) improves the contact resistance to a range of 0.8 - 2 ohm-mm but the annealing conditions strongly depend on the AlN thickness as well as the heterostructure quality (,). All alloyed contacts show smooth morphology, making them suitable for e-beam lithographically defined gate patterning. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]