摘要:

Evolution taking place under irradiation of cascade region (CR) in copper during the thermal spike has been simulated by molecular dynamics technique. It is shown that over time intervals of ∼10−12s in CR with sufficiently big sizes there is a possibility of quasimelting, during which the majority of atoms change their initial positions. The defect structure of the cascade region does not qualitatively change immediately after crystallization. However, atT≃0.7–0.8Tmvacancies, because of the temperature gradients, move preferentially towards the centre of CR. It is shown that at “fast” cooling (∼6 1014K/s) they form finally a depleted zone with higher (∼2 times) concentration of vacancies as compared to the initial one; and at “slow” cooling (∼2 1014K/s) they form a void of irregular form, which at lower temperatures (∼0.7-0.4Tmcan transform, because of the thermal pressure in CR, into the Frank dislocation loop over the period of ∼10−10s. An analysis has been made of the experimental data indicating the possibility of “slow” cooling in metals located in the middle of the periodic system and of “fast” cooling-in metals located at the end of it.

ISSN:0033-7579    

DOI:10.1080/00337578208211468

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Final products in the radiolysis of pure neopentane at 4 and 77 K have been analyzed by capillary gas chromatography. The results are inconsistent with those obtained by esr spectroscopy. The ratio C-C to C-H bond rupture in the radiolysis of neopentane is 0.3–0.5 from the product analysis at 4 and 77 K while esr spectroscopy at 4 K indicates an extremely low ratio (<0.01).

ISSN:0033-7579    

DOI:10.1080/00337578208211469

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

An investigation of the annealing characteristics of ion-implanted (40 keV N+, As+, Sb+and Bi+) GaAs at 40 K has been performed in the 40–300°K temperature range using high resolution Rutherford backscattering-channelling of 2 MeV He+ions. Isochronal annealing studies of 40 keV N+ and As+implants at 40 K to fluences below the amorphization threshold showed that annealing starts at ∼100 K and proceeds monotonically up to 300 K, resulting in fractional disorder recoveries as high as 75 %. The annealing results suggest simpler defect formation and migration for damage produced by lighter ions and comparatively more direct impact amorphization for heavy ion damage with still a large simpler defect component (∼50 %) which may be annealed. The implications of this, below room temperature, disorder recovery in the interpretation of existing data is discussed.

ISSN:0033-7579    

DOI:10.1080/00337578208211470

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

We measure diffuse X-ray scattering close to Bragg reflections in aluminium single crystals after irradiation with fast-neutrons at 4.6 K. Detailed evaluation of the data demonstrates that interstitials are located in cascades (radiusrK= 50 Å). Within a cascade the institials form small clusters. The average number of three interstitials per cluster is independent of dosage up to 2.4 × 1018n/cm2.

ISSN:0033-7579    

DOI:10.1080/00337578208211471

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The temperature dependence of the angular-differential sputtering yield of silver has been studied for low-keV, heavy ion bombardment in order to check whether thermal spikes contribute to sputtering in this energy regime. An oscillating quartz microbalance was used as detector for sputtered particles.

ISSN:0033-7579    

DOI:10.1080/00337578208211472

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The redistribution of impurity atoms implanted in Si(100) caused by Q-switched ruby-laser annealing has been studied using 2 MeV He+-backscattering plus channeling. The elements implanted were Ga, In, Ge, Sn, As, Sb, Bi, Se, Te and Kr, the projected range and the implanted dose being the same in all cases but Kr. It is found that as a result of the laser-pulse the depth profile of the impurity has broadened, while in the case of Ga, Sn, Bi and Kr we also observe a more or less pronounced surface accumulation. Channeling experiments indicate that, except for In, a considerable fraction of the impurity atoms is on or close to substitutional positions, which corresponds to concentrations which in some cases exceed the solid solubility by orders of magnitude. A computer model of solute diffusion and segregation at a moving phase boundary is described. Fitting the measured impurity redistribution with this model results in interfacial distribution coefficients exceeding values for equilibrium freezing, in some cases by orders of magnitude. The extent to which these findings provide evidence for a strictly thermal melting model based on transient melting and freezing of a surface layer is discussed.

ISSN:0033-7579    

DOI:10.1080/00337578208211473

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Measurements of diffuse X-ray scattering close to Bragg reflections, of lattice parameter changes and of glasslike, or amorphous, scattering from α-quartz single crystals after irradiation in the range of dose from 3 to 49 × 1018fast neutrons per square centimeter are reported. The measurements close to Bragg reflections and the lattice parameter changes lead to the conclusion that the neutrons create defective regions. The crystalline matrix is heavily strained by the defective regions and the symmetry and magnitude of the strain field is determined. During annealing no appreciable change of the size and the form of the defective regions is observed. The annealing seems to be closely connected to the α–β quartz phase transition.

ISSN:0033-7579    

DOI:10.1080/00337578208211474

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Results are summarized of X-ray investigations of the ordered Fe3Al alloy structure change after neutron irradiation (E>0.1 MeV) by 2 × 1023and 5 × 1023n m−2fluences and during post-radiation annealing. It was found that the process of Fe3Al alloy radiation disordering at neutron irradiation is accompanied by production of submicroregions enriched and impoverished by Al. While heating the previously irradiated alloy the newly formed submicroregions serve like nuclei to form new BCC phases unknown earlier which have been enriched and impoverished by Al. Anomalies have been found in the process of high-temperature phase transitions on heating previously irradiated alloy samples versus non-irradiated ones. It has been shown that the previous alloy irradiation results in the significant decrease of critical temperature of its “order-disorder” phase transition.

ISSN:0033-7579    

DOI:10.1080/00337578208211475

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The peculiarities of defect formation inp-Hgi-xCdxTe crystals (x=0.195−0.205) at electron irradiation (2.3 MeV, 300 K) up to 1 × 1018cm−2were investigated. It was shown that the charge carrier lifetime changed with the irradiation due to variation of the free charge carrier density and the recombination-type centre concentration. A distance of recombination centres from the valence band of 35–55 meV for the electron irradiated crystals is determined. The isochronal annealing temperature ranges for the recombination-type radiation defects and electrically active defects, induced by the irradiation, are found.

ISSN:0033-7579    

DOI:10.1080/00337578208211476

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The characteristics of particle radiation in different undulators are qualitatively compared. Features peculiar to particle radiation in crystals (natural undulators) are discussed. The effects of particle energy and initial entry conditions on particle oscillation frequency are considered. The effect of radiation friction and multiple scattering on the radiation parameters is investigated. The accuracy of a description of channelled electron emission by means of the averaged potential is checked. A criterion is suggested for checking the applicability of classic electrodynamics to a particle radiating in a crystal.

ISSN:0033-7579    

DOI:10.1080/00337578208211477

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor