The preparation of bovine 19s thyroglobulin by agarose-gel filtration

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Kinetics of solid-state reactions between zirconium thin film and silicon carbide at elevated temperatures

Solid state reactions between a thin film (133 nm) of Zr and bulk single crystalline 6H-SiC substrates have been studied at temperatures between 600 °C and 850 °C for durations of 30, 60 and 120 min under high vacuum conditions. The deposited film and reaction zones were investigated by Rutherford backscattering spectrometry (RBS) and X-ray diffraction. The RBS spectra were simulated in order to obtain the deposited layer thickness, reaction zone compositions and reaction zone thickness. The as-deposited spectra fit well with those annealed at 600 °C, thus showing there were no reactions taking place. At temperatures of 700 °C and above, Zr reacted with the SiC substrate and formed a mixed layer of Zr carbide (ZrCx) and Zr silicides (ZrSi, Zr2Si and Zr5Si3). Annealing at 850 °C for 240 min revealed that all the deposited Zr had completely reacted. The interface reaction follows the parabolic growth law thereby indicating diffusion controlled reaction kinetics. The activation energy for the diffusion process obtained was 1.6 eV in the relatively narrow temperature range 700–850 °C.http://www.elsevier.com/locate/nimbhb201

Hydrogen kinetics in a-Si:H and a-SiC:H thin films investigated by real-time ERD

Hydrogen effusion from hydrogenated amorphous silicon (a-Si:H) and amorphous silicon carbide (a-Si1 xCx:H) thin films during a temperature ramp between RT and 600 C was studied by in situ realtime elastic recoil detection analysis. Point to point contour maps show the hydrogen depth profile and its evolution with the ramped temperature. This paper proposes a diffusion limited evolution model to study H kinetic properties from total retained H contents recorded in a single ramp. In a compact a-Si:H layer where H predominantly effuses at high temperatures between 500 and 600 C, an activation energy value of 1.50 eV and a diffusion pre-factor of 0.41 10 4 cm2/s were obtained. Applied to an non-stoichiometric a-Si1 xCx:H film in the same range of temperature, the model led to reduced values of activation energy and diffusion prefactor of 0.33 eV and 0.59 10 11 cm2/s, respectively.National Research Foundation of South Africa (Grant specific unique reference number (UID) 85961).http://www.elsevier.com/locate/nimbhb201

Interface behaviour and electrical performance of ruthenium Schottky contact on 4H-SiC after argon annealing

Rutherford backscattering spectrometry(RBS) analysis , carried out at various annealing temperatures, of a thin film of ruthenium on n-type 4-hexagonal silicon carbide (4H-SiC) showed evidence of ruthenium oxidation, ruthenium silicide formation and diffusion of ruthenium into silicon carbide starting from an annealing temperature of 400oC. Ruthenium oxidation was more pronounced, and ruthenium and Silicon inter-diffusion was very deep after annealing at 800oC. Raman analysis of some samples also showed ruthenium silicide formation and oxidation. The Schottky barrier diodes showed very good linear capacitance-voltage characteristics and excellent forward current-voltage characteristics, despite the occurrence of the chemical reactions and inter-diffusion of ruthenium and silicon at ruthenium-silicon-carbide interface, up to an annealing temperature of 800oC.http://link.springer.com/journal/12034hb201

Conformal Points and Duality of Non-Abelian Thirring Models and Interacting WZNW Models

We show that the strong coupling phase of the non-Abelian Thirring model is dual to the weak-coupling phase of a system of two WZNW models coupled to each other through a current-current interaction. This latter system is integrable and is related to a perturbed conformal field theory which, in the large $|k|$ limit, has a nontrivial zero of the perturbation-parameter beta-function. The non-Abelian Thirring model reduces to a free fermion theory plus a topological field theory at this critical point, which should therefore be identified with the isoscalar Dashen-Frishman conformal point. The relationship with the Gross-Neveu model is discussed.Comment: This is a version which will appear in Nucl. Phys.

In-situ RBS studies of strontium implanted glassy carbon

The diffusion behaviour of strontium in glassy carbon was investigated using in-situ real time Rutherford backscattering spectrometry. The sample was annealed in vacuum from room temperature to 650 oC. Diffusion of the implanted strontium towards the bulk was observed after annealing at temperatures ranging from 450 oC – 560 oC. The diffusion depth was limited to the end-of-ion-range region where there were still some radiation damage present.No diffusion into the pristine glassy carbon was observed suggestion that diffusion of Sr in glassy carbon can only occur in regions with radiation damage. Annealing the sample at higher temperatures higher than 560 oC resulted in migration of the implanted strontium towards the surface of the glassy carbon substrate. The amount of the accumulated strontium at the surface increased as the annealing temperature is increased. The RBS spectra obtained after annealing the sample isothermally at 650 oC for 2 hours show that there was no further diffusion and accumulation of the strontium during this period.http://www.journals.elsevier.com/vacuum2017-04-30hb2017Physic

Solid state reaction and operational stability of ruthenium Schottky contact-on-6H-SiC under argon annealing

Thin films of ruthenium-on-6-hexagonal silicon carbide (6H-SiC) were analysed by Rutherford backscattering spectroscopy (RBS) at various annealing temperatures. Some thin film samples were also analysed by scanning electron microscope (SEM). RBS analysis indicated minimal element diffusion, and formation of ruthenium oxide after annealing at 500 oC. Large scale diffusion of ruthenium (Ru) was observed to commence at 700 oC. The SEM images indicated that the as-deposited Ru was disorderly and amorphous. Annealing of the thin film improved the grain quality of Ru. The fabricated Ru-6H-SiC Schottky barrier diodes (SBD) with nickel ohmic contacts showed excellent rectifying behaviour and linear capacitance-voltage characteristics up to an annealing temperature of 900 oC. The SBDs degraded after annealing at 1000 oC. The degradation of the SBDs is attributed to the inter-diffusion of Ru and Si at the Schottky-substrate interface.http://link.springer.com/journal/116642016-10-31hb201

Interface reactions between Pd thin films and SiC by thermal annealing and SHI irradiation

The solid-state reactions between Pd thin films and 6H-SiC substrates induced by thermal annealing, room temperature swift heavy ion (SHI) irradiation and high temperature SHI irradiation have been investigated by in situ and real-time Rutherford backscattering spectrometry (RBS) and Grazing incidence X-ray diffraction (GIXRD). At room temperature, no silicides were detected to have formed in the Pd/SiC samples. Two reaction growth zones were observed in the samples annealed in situ and analysed by real time RBS. The initial reaction growth region led to formation of Pd3Si or (Pd2Si+Pd4Si) as the initial phase(s) to form at a temperature of about 450 °C. Thereafter, the reaction zone did not change until a temperature of 640 °C was attained where Pd2Si was observed to form in the reaction zone. Kinetic analysis of the initial reaction indicates very fast reaction rates of about 1.55×1015 at.cm-2/s and the Pd silicide formed grew linear with time. SHI irradiation of the Pd/SiC samples was performed by 167 MeV Xe26+ ions at room temperature at high fluences of 1.07×1014 and 4×1014 ions/cm2 and at 400 °C at lower fluences of 5×1013 ions/cm2. The Pd/SiC interface was analysed by RBS and no SHI induced diffusion was observed for room temperature irradiations. The sample irradiated at 400 °C, SHI induced diffusion was observed to occur accompanied with the formation of Pd4Si, Pd9Si2 and Pd5Si phases which were identified by GIXRD analysis.http://www.elsevier.com/locate/nimb2017-03-31hb2016Physic

Diffusion of a mono-energetic implanted species with a Gaussian profile

The implanted profile in an isotropic substrate of a mono-energetic ion species is usually very near a Gaussian profile. An exact solution to the time-dependent Fick diffusion equation of an initially Gaussian profile is presented. This solution is a general one also covering the diffusion within the two limiting cases usually considered in solutions to the Fick equation, viz. a perfect sink at the surface and a perfectly reflecting surface plane at the surface. An analysis of the solutions for these two cases shows that at small diffusion times the main effect of annealing is a nearly symmetric broadening of the implanted profile. At the origin and for longer diffusion times the profile deviates significantly from Gaussian. A review is also given of past attempts to extract diffusion coefficients by fitting experimental data to approximate equations based on simplified initial profiles.http://www.elsevier.com/locate/nimb2018-09-01hj2018Physic