摘要:

On the basis of a numerically solved heat diffusion equation, the structure of the thermal transient induced in an aluminum sample by an electron beam pulse is described in terms of slush zone formation, molten depth, liquid phase duration, and melt front history. The heat flow dynamics, as determined by monochromatic (electron energy ranging between 5 and 25 keV) and ultrashort (15 ns fwhm) pulses, is contrasted with the ruby laser induced one. Accessible absorbed energy intervals for sample surface melting are given as a function of electron energy; heating of the sample interior at values higher than those attained at the surface is shown to occur only at higher electron energies, for a given pulse duration. The general dependence of the present results on the pulse duration and the effects produced by polychromatic pulses are also discussed.

ISSN:0033-7579    

DOI:10.1080/00337578308221720

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A pure Cu and a Cu (100 ppm Au) alloy were irradiated at 4 K with thermal neutrons. The isochronal recovery spectra (30 K-400 K) were compared with those of identical samples irradiated to equivalent defect concentrations using fast (>0.1 MeV) neutrons. The differences observed in the resultant recovery spectra could be interpreted (in view of the damage configurations) due to the different types of neutron energy involved. Direct comparison of these spectra with earlier results involving defect kinetics in thermal- and fast-neutron-irradiated Pt and dilute Pt alloys was possible.

ISSN:0033-7579    

DOI:10.1080/00337578308221721

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Specimens of pure Cu and dilute Cu-Au (100 ppm Au) were irradiated with fast neutrons (>0.1 MeV) at 4 K and isochronally annealed to 400 K. Recovery spectra were analysed for several induced-defect concentrations varying from ∼1 to 250 ppm in these specimens. Certain existing controversies relating to the recovery of fast- or thermal-neutron-irradiated materials could be satisfactorily explained if the variations in defect concentration were taken into account. The relative concentrations of irradiation-induced defects (CF) and substitutional impurities, viz.CF/CI, were seen to have a major role in the interpretations. Satisfactory comparisons could be made with recent similar studies involving thermal- and fast-neutron irradiations of Pt and its dilute alloys.

ISSN:0033-7579    

DOI:10.1080/00337578308221722

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Quenching from 875°C of doped and high purity germanium produces several deep level defects not previously reported. Subsequent γ-irradiation of this material provides evidence that most of these defects are possibly related to oxygen dispersed throughout the samples during the quench. Isochronal annealing data are given for two of the defects(Ec−0.36 eV,Ev+039 eV), and exposure to a hydrogen plasma for 2 hr at 250°C is shown to effectively neutralize deep donor levels (Ec−0.35 eV,Ec-036 eV) to a depth of ∼50 μm.

ISSN:0033-7579    

DOI:10.1080/00337578308221723

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Poly and single crystals of ordered Fe-40 at.% Al alloy were irradiated with 2.5 MeV electrons at 21 K and then annealed. Increases in the radiation-induced resistivity are interpreted in terms of the production and recombination of Frenkel-pairs. An estimate is given for the specific Frenkel-pair resistivity ρHFand for the effective recombination volumeVo. Three well-defined recovery stages were observed at 100 K, 500 K and 610 K respectively, attributed to close-pair recombination, long-range interstitial elimination at vacancies and finally vacancy elimination. A decrease below the resistivity value of unirradiated samples was always noticed above 600 K during the vacancy migration stage and attributed to an order-enhancement process. Such a behavior is discussed by comparison with the recovery of the same alloy after neutron irradiation.

ISSN:0033-7579    

DOI:10.1080/00337578308221724

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Vanadium single crystals have been low dose implanted with Ga-, Se-, Bi- and In-ions. Lattice positions have been determined with the channeling and backscattering technique. For Ga-, Bi-and In-atoms 100% substitutionality was observed. The Se-atoms were found to be slightly displaced from the substitutional lattice site. Furnace and pulsed electron beam annealing of the Se-implanted V-single crystals with energy densities insufficient for surface melting caused a further decrease of the substitutional fraction.

ISSN:0033-7579    

DOI:10.1080/00337578308221725

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Pure Pt and dilute alloys of Pt-Cu and Pt-Au were fast-neutron irradiated at 4 K, and subsequently isochronally annealed from 7 K to 750 K. The recovery spectra obtained using a resistivity method were compared with spectra of the same samples predoped with fast-neutron-irradiation-induced defects which exist above 400 K. The results could be compared favourably with existing data on prequenched and irradiated Pt. A comparison of these new results with existing data relating to the controversial 120 K and 360 K substages in Pt allowed more positive interpretations regarding the defect processes occurring at these temperatures.

ISSN:0033-7579    

DOI:10.1080/00337578308221726

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

After pulsed ruby laser annealing of tellurium implanted silicon considerable impurity redistribution is observed with little surface segregation. In the bulk, substitutional fractions of 85-90% are found, independent of the Te-concentration or the presence of phosphorus or boron. Computer simulations show that the slight narrowing of the Te-yield curves can be accounted for by the Te-vibrational amplitudes. The displacement cross-section of substitutional Te-atoms in laser annealed silicon for 2 MeV He+-ions is determined as 5.6(20) × 10−21cm2. In contrast to pulsed laser annealing, oven annealing results in strongly narrowed Te-yield curves with a high minimum yield, indicating a small true substitutional impurity fraction.

ISSN:0033-7579    

DOI:10.1080/00337578308221727

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The fraction of substitutional Te atoms in silicon deduced from temperature dependent Hall measurements is comparable to that derived from channeling experiments. The donor activation energy of these atoms is found to be about 0.19 eV. Approximately 10% of the Te-atoms give rise to a shallow donor level atEc-0.06 eV and is probably associated with a defect. Substitutional iodine is not electrically active in Si up to 450 K. From this a lower limit of the donor activation energy of 0.30 eV is estimated.

ISSN:0033-7579    

DOI:10.1080/00337578308221728

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

In this paper a new method is proposed for calculating, for any transverse energy, the diffusive nuclear contribution to the rate of increase with depth of the mean transverse energy of positively charged ions subjected to the stochastic effects of the thermal vibrations of the string atoms of a crystal.

ISSN:0033-7579    

DOI:10.1080/00337578308221729

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor