摘要:

Structural transformations in non-metallic solids induced by energetic heavy ions at intermediate (∼1013−1016ions/cm2) and high (∼ 1017ions/cm2) doses normally take the form of amorphization, crystallization, or stoichiometry changes. Using the results of 72 substances both a temperature-ratio and a bond-type criterion are shown to be successful in predicting the occurrence of amorphization or crystallization. The former, based on a physical model involving thermal spikes, states that amorphization should occur whenever the ratio (crystallization temperature)/(melting point) exceeds 0.30. The latter, of more or less empirical origin, states that amorphization should occur whenever the ionicity is ≤0.47. Stoichiometry changes are basically different from amorphization and crystallization and this is reflected in the criterion. It is shown that whether or not a substance (such as AgBr or TiO2) loses a component (such as Br or O) during bombardment correlates with the heat of atomization showing a minimum for a particular degree of loss.

ISSN:0033-7579    

DOI:10.1080/00337577508242047

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The electron paramagnetic resonance of x-irradiated (∼10 krad.) tyrosine, thyronine and their iodine-derivatives in the form of compressed pellets in vacuum-sealed quartz tubes have been measured between 100 K and 300 K at ∼9 GHz. The EPR spectra of tyrosine, 3–5 diiodo thyronine and thyronine, in the order of decreasing line-width, are spectrally similar singlets with g = 2.004 or 2.005 and hence indicate that the electron spin density is trapped mainly in the ring from which the hydroxyl proton is lost. The samples having iodine on the same ring as the OH group show a rather large anisotropy in g ≊ 2.04 presumably due to the presence of small spin density on the iodine(s).

ISSN:0033-7579    

DOI:10.1080/00337577508242048

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The unsaturable trap model, which attributes the increase of the electrical resistivity of fcc metals during electron irradiation in the temperature regime of Stage-II recovery to the trapping of Stage-IEinterstitials at impurity atoms, is shown to be in serious disagreement with the experiments, contrary to opposite statements in the literature. As shown recently, the predictions of the unsaturable trap model are independent of the dimensionality of the diffusion of the Stage-IEinterstitials. Previous attempts to rule out a one-dimensional migration of the Stage-IEinterstitials (and hence the two-interstitial model) on the basis of the alleged agreement of the unsaturable trap model with Stage-II damage curves are thus meaningless. On the contrary, it is demonstrated that the two-interstitial model accounts for minute details of the measured Stage-II damage curves in a natural way.

ISSN:0033-7579    

DOI:10.1080/00337577508242049

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The dose dependence of lattice disorder produced by implanted argon ions of energy 200 ke V has been investigated for doses between 2 × 1013/cm2and 1 × 1017/cm2and four implantation temperatures, -196°C, 20°C, 200°C and 400°C. The radiation damage was determined by means of the channelling technique with 1.4 MeV He+-ions.

ISSN:0033-7579    

DOI:10.1080/00337577508242050

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Argon ion scattering by the (110) face of a copper crystal is experimentally investigated. The obtained data are discussed in terms of simplest model of blocking effect.

ISSN:0033-7579    

DOI:10.1080/00337577508242051

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The process of disordering of structure of silicon crystallite being initially diamond-like was studied with the method of computer simulation under the action of the thermal excitation, which can be developed at the radiation damage as well. The central potential of interatomic interaction extended to two coordination spheres was used. Simulation results are compared with experimental results of the study of structure of silicon amorphous films with the electron diffraction method.

ISSN:0033-7579    

DOI:10.1080/00337577508242052

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Voids created during neutron irradiation lead to volume welling and changes in the elastic properties of metals. Present theoretical treatments of the effect of voids on elastic constants do not consider the possible effect of gas pressure or surface stresses within the voids. These corrections have been determined for the change in bulk modulus. Although parameters required for numerical evaluation are not available for materials of technological interest (e.g. stainless steels), values for copper indicate that various correction terms tend to cancel. Thus, gas pressure should not be important in predicting elastic property changes caused by voids, and conversely, experiments involving elastic property measurements are impractical as a method to determine gas pressure within voids.

ISSN:0033-7579    

DOI:10.1080/00337577508242053

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

20 keV monatomic and 40 keV diatomic As ions have been implanted into GaAs at room temperature and the resultant radiation damage measured by means of the channeling and back scattering of 1 MeV He+ions. The energy density within each diatomic cascade is approximately twice the density within the monatomic cascade. The radiation damage resulting from the diatomic implant is observed to be significantly larger (two to three times) than from the monatomic implants. This observation shows, quite directly, that when significant annealing of damage is occurring during implantation one cannot adequately describe the damage production in terms of quantities averaged over the implanted layer; account must be taken of the character (e.g. energy density) of the individual damage cascades.

ISSN:0033-7579    

DOI:10.1080/00337577508242054

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Spreng and his co-workers1have studied radiation enhanced diffusion in gold-silver alloys at low temperatures. Their research technique consisted in analysing the decrease in amplitude of short wavelength composition modulations produced in film samples under irradiation with an electron current of 1.2 · 1013cm−2sec−1at 2 MeV at 77°K. The decrease in amplitude thus discovered, has been attributed to diffusion due to free migration of interstitials to sinks; consequently, the above effect seems to prove the existence of free migration of interstitials at temperatures of the annealing stages I and II for radiation defects.

ISSN:0033-7579    

DOI:10.1080/00337577508242055

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Ion implantation is now finding applications in many diverse fields1, 2, 3in addition to its established use for the fabrication of electronic devices. For such purposes it is essential that fundamental data on the spatial distribution of implanted ions be available. The Lindhard, Scharff and Schiøtt (LSS) theory4for the slowing down of energetic ions in solids enables range distributions in amorphous solids to be predicted. Measurements of ion ranges at low doses using a variety of techniques have proved the general validity of this theory.5In some circumstances, however, the conditions employed in an implantation experiment may produce a range profile different to that predicted theoretically, and hence direct experimental measurement becomes essential.

ISSN:0033-7579    

DOI:10.1080/00337577508242056

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor