摘要:

Longitudinal dopant distribution along ion tracks in soft (polymers [1–5]) and hard (diamond [6,7]) condensed carbonaceous matter have been studied by neutron depth profiling and cathodoluminesence. Both in-diffusion from the aqueous phase and energetic ion implantation were used in primary track doping.In-situself-decoration of tracks and post-implantation with a secondary ion species were used in the specific case of ion implantation. Radial dopant distributions were also studied by means of a modified tomographic procedure. Decorative doping of ion bombarded solids is useful in probing track structure, and especially in pointing the way to potential development of nanometric-sized electronic devices.

ISSN:1042-0150    

DOI:10.1080/10420159408224299

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The paper describes angular distributions of channeled particles in thick single crystals. It is shown that the distribution of channeled particles over the angles may be calculated if the statistical equilibrium in the transverse phase space takes place. The results obtained in computer simulation are compared with analytical calculations for axially channeled electrons. It is shown, that due to the influence of the continuum string potential the angular distribution in the oriented crystal becomes essentially broader then one in an amorphous medium.

ISSN:1042-0150    

DOI:10.1080/10420159408224300

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Thermal atom deposited thin films are usually under dense, voided and in a state of tensile stress. Simultaneous ion bombardment during film growth can increase density, modify tensile stress and even generate compressive stress. The present analysis evaluates a number of collisionally motivated densification processes and predicts the dependence of tensile stress evolution, in each case, upon the parameters of ion flux density and ion energy and atomic deposition rate. A further set of models for the development of compressive stress, associated with dislocation loop and dislocation formation either by direct interstitial loop punching from collision cascades or by agglomeration and capture of freely migrating interstitials, are also considered. More complex dependences upon processing parameters and possible dependence upon film thickness are deduced.

ISSN:1042-0150    

DOI:10.1080/10420159408224301

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We study temperature programmed desorption of sodium and chlorine from an electron irradiated sodium chloride (100) surface. In this experiment, the sodium chloride crystal is irradiated with 500 eV electrons. After the electron beam is turned off, the crystal is heated and desorption of the alkali atoms is observed. This delayed desorption of sodium is analyzed using fractional order desorption equations. The results clearly show that the desorption is not a first order process. The data are interpreted in terms of a thick layer of sodium forming on the surface.

ISSN:1042-0150    

DOI:10.1080/10420159408224302

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Synthetic single-crystals of zircon [(100) growth surfaces] were implanted at 77K with 540 keV Pb ions with fluences of 3.3 × 1011to 5 × 1015ions/cm2—a dose range that completely spans the crystalline-to-amorphous transition as determined by Rutherford backscattering/ion-channeling measurements. A chemically unzoned, natural crystal [polished (100) section] was similarly implanted. Both the natural and synthetic crystals, as examined by mechanical-properties microprobe (MPM) methods, exhibited an overall radiation-induced softening (70% reduction) and decrease in modulus (42%) through the crystalline-to-amorphous transition. This transition occurs over a narrow range of dose, i.e. 1 × 1013to 1 × 1014Pb ions/cm2. Moreover, below the transition, a pronounced radiation-induced hardening occurs in the near-surface region of the synthetic crystals. This radiation hardening may be due to the accumulation of interstitials. In contrast, the natural zircon showed no hardening; however, its initially higher hardness values suggest that it was already hardened. Despite the continued re-damage process (due to overlapping of displacement cascades) for ion doses beyond the saturation value of 1 × 1014ions/cm2the hardness remains constant.

ISSN:1042-0150    

DOI:10.1080/10420159408224303

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The optical behaviour of colour centres is studied in thin films of KCl obtained by thermal evaporation onto amorphous substrates. Deposition conditions are optimized in order to minimize chemical and thermal effects on films. Concentration of colour centres even higher than in bulk crystals can be induced by low energy electron irradiation. Thermal bleaching of F centres is observed at room temperature and its kinetics, deduced from absorption measurements, consists of two exponential processes with very different time constants. Luminescence is obtained for the first time from aggregate colour centres in KCl films, and typical emissions of F2, F3, F4defects (but not of F centres because of concentration quenching) are revealed.

ISSN:1042-0150    

DOI:10.1080/10420159408224304

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The precipitation kinetics of Cu in a binary Fe-Cu 1.34% at. alloy, for thermal aged and irradiated samples, is followed theoretically. The model considers nucleation, growth, and coarsening as concomitant processes and takes into account interaction between precipitates. Assuming that: a) the only effect of irradiation is to enhance copper diffusion and b) the precipitate nuclei are present at the beginning of the experiments, not depending their number on temperature, theoretical calculations fit well experimental results, obtained by electrical resistivity measurements.

ISSN:1042-0150    

DOI:10.1080/10420159408224305

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The nucleation of helium bubbles during the isochronal annealing of helium-implanted niobium has been studied by positron annihilation measurements. The evolution of implantation-induced radiation damage before the nucleation stage consists of processes such as the dissociation of helium from dislocation loops, coarsening of vacancy clusters, helium-vacancy interaction and loop annealing. The helium bubble nucleation stage is characterised by a remarkable decrease in the positron lifetime and is observed in the temperature interval from 750°C to 850°C. The stabilization of the helium bubbles in the post-nucleation stage has been attributed to the effects of segregation of impurities on the bubble surfaces. The positron lifetime data in the helium bubble regime has been analysed in terms of the positron surface-state model, which revealed the presence of overpressurized bubbles. The properties of the helium bubbles observed in the present work have been compared with those of athermal bubbles reported in earlier studies. A lower limit of 4.7 eV for helium-vacancy binding energy in niobium has been obtained. The helium-vacancy binding appears to be stronger than hydrogen-vacancy binding in niobium.

ISSN:1042-0150    

DOI:10.1080/10420159408224306

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Isothermal decomposition of sodium bromate at temperatures: 613, 633 and 653 K occurs through (i) initial gas evolution, (ii) short induction period, (iii) acceleratory and (iv) decay stages. Irradiation as well as doping shorten the induction period; I, facilitate the rate of reaction in the last two periods, without affecting the initial puff of gas. The combined effect of these treatments eliminate the induction period and increase the extent of decomposition remarkably. The data are best fitted to Prout-Tompkins mechanism exploring that nucleation occurs in a chain-branching manner, the nature of which remains unaltered by these treatments.

ISSN:1042-0150    

DOI:10.1080/10420159408224307

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Electron paramagnetic resonance spectra of xCoO. (0.4-x) BaO.0.6 B203glasses (0⩽x⩽0.25) Containing 2 mol% V2O5have been studied in the X band and at 300 and 90 K. Spin-Hamiltonian parameters of the V02+ions have been calculated. It is found that for x⩽0.12 the octahedral symmetry on V4+site is improved when BaO is replaced by Co O and for x>0.12 hyperfine spectra are not observed.

ISSN:1042-0150    

DOI:10.1080/10420159408224308

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor