摘要:

The substitutional fraction,fsof Co implanted into Al single crystals depends on the substrate temperature and on the Co concentration. Implantation at 293 K reveals an anomalous increase offsat low concentrations and reaches maximumfsvalues of 0.40 ± 0.04 for concentrations between 0.12 at.% and 0.4 at.% Co. At 77 Kfsis 0.63 ± 0.04 for concentrations between 0.08 at.% and 1 at.% Co. The non-substitutional Co fraction, 1-fsis governed by Co-vacancy complexes which form within the collision cascade and by additional trapping of mobile vacancies at 293 K. The decrease offsat high Co concentrations, which was observed for both the 77 K and the 293 K implants, is due to a transition into a disordered, probably amorphous phase. Implanting similar Co-concentrations, the disordered phase fraction is larger for 77 K implants.

ISSN:1042-0150    

DOI:10.1080/10420159108221359

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The damage rate (electrical resistivity increase per fluence unit δρ/δΦ) has been measured in cubic tantalum carbides TaC0.99and TaC0.80, during irradiation at 21 K by electrons of energiesEranging from 0.4 to 2.7 MeV. Both experimental δρ/δΦ versusEcurves clearly display two thresholds atE< 0.35 MeV andE< 1.5 MeV. Comparison with theoretical displacement cross-sections calculated for TaC allowed us to attribute unambiguously the first threshold to carbon displacements and the second one to tantalum. Surprisingly, in the largely substoichiometric TaC0.80sample, irradiation still creates carbon Frenkel pair type defects. Taking into account the real irradiation conditions, the deduced parameters areTCd= 28 ± 6eV andTdTa= 42 ± 2eV for the threshold displacement energies in TaC0.99(resp. 28 ± 6 and 32 ± 2eV in TaC0.80), and ρCF= 26 ± 5 μΩ-cm/at.%. for the specific mean resistivity of carbon Frenkel pair in TaC0·99.

ISSN:1042-0150    

DOI:10.1080/10420159108221360

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Vacuum-sublimed films of C60molecules with thicknesses of 180–300 nm were irradiated with 100- or 200-keV protons at room temperature. The effects of fluences of 3.3 × 1014to 6.1 × 1016H/cm2have been examined in detail using Fourier transform infrared (FTIR) spectrometry, glancing-angle X-ray diffraction (GXRD) and low-energy X-ray fluorescence (LXRF). All three techniques indicated that the major changes occurred for fluences greater than 1 × 1015H/cm2. Intensities of the C60FTIR peaks decreased exponentially with fluence without significant peak shifts or peak width changes. This suggests that each C60molecule was destroyed in a catastrophic event, rather than a gradual process. Because essentially all the energy deposited in the films by the protons was in the form of electronic excitation and because solid C60is an electrically insulating material, a Coulombic, or ionic, explosion at each C60molecule is proposed to explain the observations. For the larger fluences, the presence of broad FTIR bands near 740 and 1420 cm−1and the absence of sharp diffraction peaks in GXRD were taken as evidence that the C60films were transformed into a form of amorphous carbon.

ISSN:1042-0150    

DOI:10.1080/10420159108221361

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The Monte Carlo simulation code ACAT has been applied to investigate the angular distribution and the energy distribution of atoms sputtered from Cu and Nb targets by normally incident Ar+ions. It is found that there are two important effects which affect the angular distributions and the energy distributions of sputtered atoms, i.e.,the anisotropic effectandthe bulk recoil effect.The former effects means that the recoil flux keeps the memory of the incident ion-beam direction because of the incomplete cascade, while the latter one means the contributions of recoils generated at the deeper layer to the angular and the energy distributions of sputtered atoms.The anisotropic effectis important in the low energy region, and it makes the angular distribution under-cosine and the high energy tail of the energy distribution fall off faster than the Thompson distribution.The bulk recoil effectmakes angular distribution be over-cosine and the peak position of the energy distribution be shifted to somewhat higher energies.

ISSN:1042-0150    

DOI:10.1080/10420159108221362

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

It is shown in this paper that sensitization results when some alkali halide phosphors are subjected to electrolysis. This electrolytic sensitization could be attributed to the V type introduced during the electrolysis. It is suggested that such sensitization may be obtained in other phosphors which are important for the dosimetry of ionizing radiations using thermoluminescence.

ISSN:1042-0150    

DOI:10.1080/10420159108221363

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

According to a straightforward method, the spin-lattice coupling coefficientsG11andG44for MgO: Fe3+crystal are calculated theoretically by using the formulas obtained from the spin-orbit coupling mechanism and the relativistic mechanism. Based on this, the local strains in the vicinity of Fe3+ion, which is different from the bulk ones, have been investigated. The results are compared with those obtained from the superposition model analysis.

ISSN:1042-0150    

DOI:10.1080/10420159108221364

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

It is found that electron irradiation, in an electron microscope, of oxidized silicon small particles (nanometers to microns in size) supported on amorphous carbon films, produce extensive surface damage of the oxide layer. During irradiation, the sputtering of the entire thickness (many nanometers) of the silica layer was observed except for a thin (∽ 1 nm) uniform layer which remained stable to further irradiation. The sputtered silica came off and deposited on the nearby carbon film, and was identified using electron energy loss spectroscopy. The carbon film surrounding the particles was seen to damage drastically during irradiation. The damage of the oxide layer seems to be catalyzed by the carbon film at the SiO2/C interface since the rate of removal of the oxide layer decreases as the supporting carbon film disintegrates and is much slower for particles that are not supported.

ISSN:1042-0150    

DOI:10.1080/10420159108221365

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Sodium depth profiles in implanted sodium β″-alumina single crystals have been measured by the nuclear resonance technique. A systematic investigation of the depth profile modifications as function of the implanted ion energy has been done using argon-ion (E= 50–600 keV) irradiation at fixed dose (Φ = 4 × 1016ions/cm2) and beam current (I= 1 μA/cm2). Argon doses were checked by Rutherford backscattering spectrometry. The changes in the sodium profiles are discussed in terms of transport equations which include three main processes: radiation enhanced transport, electric field assisted migration, and preferential surface sputtering of the alkali element. Special attention is devoted to the discussion of sputtering processes.

ISSN:1042-0150    

DOI:10.1080/10420159108221366

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor