ISSN:1042-0150    

DOI:10.1080/10420159108213106

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Anomalies of the implanted dopant diffusion in Si often cannot be interpreted unambiguously.1The presence of free vacancies in the layer results in the essential enhancement of boron diffusion in Si.2There is a temperature for each semiconductor material when the probability for any defect associations to exist in the implanted layer (IL) during implantation is extremely small and non-equilibrium point defects only exist in it. We consider such a defect state as a physical criterion for applying the term of High Temperature Ion Implantation (HTII). Application of the HTII technique enabled us to obtain the deep penetration of the implanted dopant. The boron penetration (E= 40 keV,j= 40 μA/cm2,D=1.1016ion/cm2) ranged in depth up to 4.5 μm atTir= 1150°C.

ISSN:1042-0150    

DOI:10.1080/10420159108213107

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Secondary emission of doubly-charged postive ions from 3–15 keV Cd+ion-bombarded polycrystalline Nb and V samples at target current densities (Jp) in the range 0–1.4 mA cm−2has been studied in detail. For each target the ratio of doubly-charged to singly-charged ion currents (Is++/Is++)has been found to be 0.01 at low beam current densities and does not vary appreciably with increase in the primary ion current (Ip), there is a rapid increase in the value ofIs++as compared toI+ssuch that atJp∼ 15μm UA cm−2, the ratioIs++/Is+increase by 10 to 300 times depending upon the target and bombarding conditions. The value ofJpat which maximum enhancement ofIs++is observed often corresponds to the saturation region in the current density variation curve, observed in case of singly-charged ion emission. This region possibly corresponds to the formation of an intermetallic compounds layer of a definite stochiometric composition due to the action of reactive Cd+ions at the metallic target surface under energetic ion bambardment. By monitoring the doubly-charged ion intensity, it has become possible, to some extent, the characterize the layer. Reactive Cd+ion bambardment of metal (M) surfaces at high beam current densities leads to the formation of a MCd2-like structure and consequently, doubly-charged secondary ion emission occurs via breaking of chemical bonds corresponding to that particular structure.

ISSN:1042-0150    

DOI:10.1080/10420159108213108

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The profiles of boron ions impinging along the axis of silicon single crystal at energies in the 80–700 keV range were measured by SIMS. By a simple subtraction procedure the distributions for aligned incidence of the beam were decomposed into a random and into a channeled profile. The corresponding mean ranges,Rr, for random andRcfor channeled particles, as well as the “maximum” rangeRmfor well-channeled particles were compared with values calculated by appropriate theoretical models. For well-channeled particles the reduced electronic stopping power in the center of the channel was calculated assuming an exponential dependence of the impact parameter. It turned out. that all measured values could be reproduced by this theoretical model.

ISSN:1042-0150    

DOI:10.1080/10420159108213109

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Single crystlas of cadmium telluride have been irradiated in a high energy electron microscope. During exposure to the electron beam, extended defects which are interstitial type dislocation loops are created. The influence of experimental parameters on the loops characteristics has been investigated. Chemical Reaction Rate Theory has been developed in order to account for the kinetics of loop growth. In this way the elementary processes and their corresponding activation energies have been identified. It has been shown that the migration energy is modified around point defects and that, as a consequence, the interstitial-interstitial agglomeration energyEiis different from the intersitial-vacancy annihilation energyEv, = 0.35 eV,Ev= 0.25 eV. The comparison between experimental and theoretical data has shown that small clusters are not stable and the dissociation energy of an atom from a low size aggregate isEd= 1.1 eV. The effects of surfaces have been considered and two different treatments have been developed. This investigation has allowed us to point out that the surface efficiency is not so high as predicted by diffusion theory and that screening effects have to be considered. These latter could be the local diffusion of interstitial towards the dislocation loops.

ISSN:1042-0150    

DOI:10.1080/10420159108213110

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This contribution examines the influence of nitrogen impurity on the radiation detecting properties of synthetic diamonds. The relatively low sensitivity of the commonly available synthetic diamonds, when used as dosimeters/detectors, is attributed to the presence of nitrogen. A systematic decrease of the nitrogen level shows an increase in the radiation detection sensitivity of these crystals, and below the 25–50 ppm level the increase is even steeper. Experimental evidence strongly suggests that the nitrogen, which is generally accepted to appear in synthetic diamond in dispersed paramagnetic form, not only acts as a radiationless recombination centre for charge carriers (with an estimated hole capture cross section of ≈10−12cm2), but also affects the amount of traps formed in the synthesis of diamonds. This dual role of nitrogen which is suggested by the accumulated data is found to be consistent with a two-state model that is composed of a trapping and a recombination centre.

ISSN:1042-0150    

DOI:10.1080/10420159108213111

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The present study deals with the effect of charged particles being focused by crystals. An intial wide divergent beam falls on a crystal and it turns out that the beam density along the channeling directions is often higher than without a crystal. Thus a crystal not only disperses the particles but can also concentrate them along special directions.

ISSN:1042-0150    

DOI:10.1080/10420159108213112

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The formation of complex ions and molecules created in alkali bromides after X-irradiation at room temperature are studied by means of Resonant Raman Scattering. In NaBr, RbBr and CsBr, Br3−-type defects are formed. In NaBr only, Clusters of bromine, (Br2)nare also observed. The process of halogen clustering is related to the formation of vacancies during the irradiation in the cationic sublattice. For comparison purpose, it is shown that similar results are obtained in mixed iodide crystal, KxRb1−x, I, in which iodine aggregates are not observed whereas they are in Ki irradited in similar conditions.

ISSN:1042-0150    

DOI:10.1080/10420159108213113

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

EPR spectra of Cu2+ions doped in a strontium maleate tetrahydrate and magnesium bis (hydrogen maleate) hexahydrate have been studied inX-band at room temperature and at liquid nitrogen temperature. Spin-Hamiltonian parameters have been calculated. Molecular orbital coefficients are obtained by correlating optical absorption data with EPR results.

ISSN:1042-0150    

DOI:10.1080/10420159108213114

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In this paper we report for the first time thermoluminescence in mixed alkali sulphate materials. Very intense thermoluminescence was found out in most of the phosphors, emission in Eu doped NaKSO4and LiNaSO4being much stronger than that observed in even the applied materials like CaSO4,: Dy. The glow peaks in most of the phosphors were rather too close to room temperature to prevent the fading. It is suggested that the improved preparations might increase the glow peak temperature and then these phosphors will be better than CaSO4: Dy.

ISSN:1042-0150    

DOI:10.1080/10420159108213115

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor