Showing papers in "Radiation Effects and Defects in Solids in 1979"
TL;DR: In this article, MeV 4He backscattering and X-ray diffraction analysis were used to examine the intermixing of niobium thin films on single-crystal silicon during 28Si+ ion bombardment.
Abstract: MeV 4He backscattering and X-ray diffraction analysis were used to examine the intermixing of niobium thin films on single-crystal silicon during 28Si+ ion bombardment. The ambient temperature dependence of the intermixing is reported. The dependence cannot be explained by either radiation-enhanced diffusion or cascade mixing alone. The silicides, NbSi2, and Nb5Si3, were both observed. Silicide growth was found to be proportional to the square root of the fluence for the case in which the ion range exceeds the film thickness.
114 citations
TL;DR: In this paper, the porosity of quadratic holes of uniform shape on a planar surface is investigated and the results apply directly to nuclear tracks of rhom-boidal cross section as found in mica.
Abstract: Statistical distributions of quadratic holes of uniform shape on a planar surface are investigated Analytical calculations give expressions for the effective porosity, and the probability and areal dispersion of multiple holes of multiplicity n ≤ 2 as function of nominal porosity Computer simulations give a simple expression for the effective porosity due to hole overlap, further the probability of multiple holes of multiplicity n ≲ 50, and the areal dispersion of holes of multiplicity n ≲ 7, taking into account closed rings of multiple holes forming islands The results apply directly to nuclear tracks of rhom-boidal cross section as found in mica They give a good approximation for convex holes with inversion symmetry as eg circular holes They can be interpreted in terms of the multiple hit theory in radiation biology The range of porosity investigated reaches beyond the realm of mechanically stable nuclear track filters into the realm relevant for surface micromachining
60 citations
TL;DR: In this article, the author was a Visiting Scientist at the Department of Engineering Physics and Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada and funded by Social Sciences and Humanities Research Council of Canada.
Abstract: Work initiated whilst the author was a Visiting Scientist at the Department of Engineering Physics and Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada and funded by Social Sciences and Humanities Research Council of Canada.
58 citations
TL;DR: In this article, the authors measured the thermal desorption spectra for helium attached to xenon atoms in a tungsten crystal and found that the binding energy of the helium was found to increase monotonically with the number of helium atoms occupying the trap.
Abstract: Thermal desorption spectra have been measured for helium attached to xenon atoms in a tungsten crystal. The xenon was implanted at 1.5 keV and annealed to 2150 K, and the helium then injected at 250 eV along the direction normal to the crystal surface. The binding energy of the helium was found to increase monotonically with the number of helium atoms occupying the trap, from 1.2 eV for a single atom to ≈2.1 eV for 7 to 10 atoms. At still higher injected doses, the attachment of up to 100 helium atoms to each trap has been observed. The binding energy continues to increase to ≈4 eV for 100 atoms, and the apparent trapping radius increases by a factor of four from the empty trap value of 3.3 A.
48 citations
TL;DR: In this paper, the accumulation of amorphousness as a function of irradiation fluence in a composite model of disorder production was studied and the model was extended to the case of nuclear irradiation.
Abstract: (1979). The accumulation of amorphousness as a function of irradiation fluence in a composite model of disorder production. Radiation Effects: Vol. 43, No. 1, pp. 19-24.
47 citations
TL;DR: In this paper, a detailed composite model of amorphousness production during ion irradiation of semiconductors at low temperatures and the stepwise approximation to the disorder density profile for disorder accumulation is presented.
Abstract: A detailed composite model of amorphousness production during ion irradiation of semiconductors at low temperatures and the stepwise approximation to the disorder density profile for disorder accumulation is presented. Numerical calculations of this and other models are performed and a series of comparisons are made. It is shown that all the models considered can result in numerically similar amorphousness-ion fluence curves and hence that interpretation of experimental data of this kind can be difficult. It is further shown that if in an experimental procedure disordered but not amorphous regions are also analysed then the resulting disorder-fluence curves can be misleading and almost impossible to interpret without further analyses of, for example, dose rate effects or direct observation of defect density.
46 citations
TL;DR: In this article, the theoretical and experimental ranges and straggling values of heavy ions are compared in the energy region where the nuclear stopping dominates, using two Monte-Carlo methods and the principles of the LSS theory.
Abstract: Some theoretical and experimental ranges and straggling values of heavy ions are compared in the energy region where the nuclear stopping dominates. In the calculations, two Monte-Carlo methods and the principles of the LSS theory were used. In most cases rather good consistency is obtained, if Dirac-Fock electron distributions and Monte-Carlo methods are used. The effects of the solid properties of the stopping medium on the ranges are estimated to be small. A stopping power curve based on a mean Dirac-Fock potential, when the LSS theory is corrected, is presented.
45 citations
TL;DR: In this article, the defect microstructure induced in single-crystal aluminum oxide by bombardment with high-energy ions has been studied by transmission electron microscopy (TEM) and the effects of the irradiation temperature, the type of ion used for irradiation, and the presence of inert gas atoms upon the micro-structure were examined in detail.
Abstract: The defect microstructure induced in single-crystal aluminum oxide by bombardment with high-energy ions has been studied by transmission electron microscopy (TEM). The effects of the irradiation temperature, the type of ion used for irradiation, and the presence of inert gas atoms upon the microstructure were examined in detail. The intrinsic, displacement-induced defect structures which resulted from ion bombardment appeared quite similar to the microstructures of aluminum oxide subjected to fast neutron or high energy electron irradiation at similar temperatures and doses. The most significant changes in the microstructure were caused by bombardment with helium ions. Implantation of helium into alumina at low temperature followed by annealing at high temperature resulted in the formation of a dense dislocation network. The large number of defects required to account for this network may have arisen from strong trapping of helium by radiation-induced vacancies, which left a large population of i...
43 citations
TL;DR: A luminescence band at 450 nm (2.7 eV) was observed during ion irradiation of fused silica at energies between 0.7 and 2.0 MeV as mentioned in this paper.
Abstract: A luminescence band at 450 nm (2.7 eV) is observed during ion irradiation of fused silica at energies between 0.7 and 2.0 MeV. The intensity is a function of dose and ion species. In general, the intensity increases to a maximum at which it appears to remain for light ion excitation (H+, He+), but from which it subsequently decays for heavy ions (N+, O+). The energy deposition required to produce this maximum signal is of the same order as that reported for other saturable damage parameters in silica (such as the compaction associated with bond reorientation, and changes in the refractive index).
41 citations
TL;DR: In this article, the energy loss, angular distribution and charge fraction of hydrogen transmitted through thin carbon foils in the energy range 200 ≤ E ≤ 3000 eV have been measured and the measured angular distributions were narrower than those predicted by the theory of Meyer except at the highest energies and thinnest foils.
Abstract: The energy loss, angular distributions and charge fractions of hydrogen transmitted through thin carbon foils in the energy range 200 ≤ E ≤ 3000 eV have been measured. The values of the stopping power constant equal 4.18 ± 0.30 and 4.38 ± 0.34 (eV)1/2 cm2/μg, where the two values are the result of using the most probable final energy and the average final energy, respectively. These values agree well with the theoretical value of 4.09 (eV)1/2 cm2/μg. The measured angular distributions were narrower than those predicted by the theory of Meyer except at the highest energies and thinnest foils. The fractions of particles emerging from the foil as positive ions, f+ , and negative ions, f −, as a function of the exit energy are given by f+ (%) = 3.0 E and f− (%) = 2.3 E, where E is in keV.
37 citations
TL;DR: In this paper, the authors investigated the generation of blisters due to irradiation by helium ions and the possible pressure in helium bubbles in metals, the binding energy of helium atoms and vacancies to a bubble, and the kinetics of bubble growth.
Abstract: The generation of blisters due to irradiation by helium ions is investigated theoretically. The possible pressure in helium bubbles in metals, the binding energy of helium atoms and vacancies to a bubble are calculated. The kinetics of bubble growth is studied. Using the known profiles of implanted ions and defects, the gas pressure in bubbles and the stress in a layer are computed as a function of the layer depth, x. Supposing that a crack is formed, at a depth of maximum stress, at the moment, when the stress reaches the point of fracture, expressions for the depth of crack generation and of the critical dose of blister formation are obtained. They are in good agreement with experiment. Estimations of the gas quantity discharged in the crack and of integral lateral stress in an irradiated layer are given. On the basis of these estimations, a conclusion is made of a possibility of blister buckling as being due to pressure inside the blister, on account of the inner stresses in the blister cover....
TL;DR: In this article, self-supporting carbon foils of typical areal density (5-10), μg/cm2 are irradiated with (0.1-1.0)μA/mm2 Helium ions at (100-400) keV.
Abstract: Self-supporting carbon foils of typical areal density (5–10), μg/cm2 are irradiated with (0.1–1.0)μA/mm2 Helium ions at (100–400) keV. Characteristic variations of the surface and the crystallographic structure of the foils are observed. A reduction of the optical transmission is accompanied by a contraction of the irradiated region resulting in wrinkles within the non-irradiated parts. By means of electron diffraction a continuous crystallographic transformation (graphitization) in the foil is observed. The rate of graphitization depends on the current density. the energy of the projectiles and the time of irradiation. It is shown that the same kind of crystallization can be produced by heat treatment of the foils with temperatures up to 1300 K.
TL;DR: Au films deposited on Si substrates have been sputtered by 20 and 100 keV Ar bombardment, respectively as discussed by the authors, at film thicknesses considerably larger than the projectile range.
Abstract: Au films deposited on Si substrates have been sputtered by 20 and 100 keV Ar bombardment, respectively. Bombardment-induced intermixing of Au and Si was observed at film thicknesses considerably larger than the projectile range. Due to radiation-enhanced diffusion, the partial sputtering yield of Au from Si-Au alloys decreases with increasing fluence. Complete removal of Au from Si is impossible if Ar ions are used for sputtering.
IBM1
TL;DR: In this article, a review of techniques for electrical measurement of high current ion beams is presented, and a computer analysis of the secondary-particle current collection schemes is made for dosimetry-cup configurations commonly used on ion implanters with electrostatic scanning.
Abstract: A review of techniques for electrical measurement of high current ion beams is presented. A computer analysis of the secondary-particle current-collection schemes is made for dosimetry-cup configurations commonly used on ion implanters with electrostatic scanning. The design of a dosimetry cup for a high current implanter with mechanical scanning is discussed. Also beam monitoring techniques for uniformity measurements are reviewed.
TL;DR: In this paper, the stopping powers of Al, Ti, Ni, Cu, Zn, Mo, Ta, W and Au were measured over the energy range Ep = 0.3-1.5 MeV by the elastic backscattering technique.
Abstract: The stopping powers of Al, Ti, Ni, Cu, Zn, Mo, Ag, Ta, W and Au for protons were measured over the energy range Ep = 0.3–1.5 MeV by the elastic backscattering technique. In the case of Al, Cu, Ag and Au the thin-film method was used. The areal densities of the films were gravimetrically measured. The thick-target scattering yields were employed in the calculation of the stopping powers of Ti, Ni, Zn, Mo, Ta and W relative to those of the absolute measurements. The experimental accuracy of the absolute stopping values is estimated at 1.5–2.5% and that of the relative values at 2.2–3.5%. The results obtained were compared with the best-fit values from a recent compilation (Hydrogen Stopping Powers and Ranges in All Elements, H. H. Andersen and J. F. Ziegler) and earlier available absolute data. The values of the present experiment agree rather well at the high-energy end with the “best-fit values”. At low energies there occur discrepancies, the present data being usually a few per cent lower than t...
TL;DR: The formation of extended glassy shapes under ionic bombardment is an alternative method of formation of some of the glassy constituents of chondrules, tektites and lunar agglutinates by cosmic irradiation as mentioned in this paper.
Abstract: Zirconium silicate powder is converted into a range of metamict conditions, and finally to a non-crystalline condition by Argon or Krypton ion bombardment of energies of 1 to 3.5 MeV. The non-crystalline condition is induced by approximately 2 × 1015 ions per cm2. Further irradiation causes the non-crystalline particles to bloat into extended disc shapes. The glassy metamict state creeps under heavy ion irradiation. Under comparable conditions, silicates such as a-quartz bloat into a similar range of glassy shapes, whereas nitrides such as Si3N4 do not. The metamict state is essentially a glass-type random atomic structural arrangement. This formation of extended glassy shapes under ionic bombardment is an alternative method of formation of some of the glassy constituents of chondrules, tektites and lunar agglutinates by cosmic irradiation. The reported sintering under fast neutron irradiation may be explained by the joining of neighboring particles under glassy irradiation creep.
TL;DR: A Fully Dynamic Rate Theory (FDRT) has been used in the computer code TRANSWELL to analyze the response of metals during steady-state and pulsed irradiations.
Abstract: A Fully Dynamic Rate Theory (FDRT) has been used in the computer code TRANSWELL to analyze the response of metals during steady-state and pulsed irradiations. This paper correlates the FDRT with experimental data on void growth in metals. It is shown that the theory is successful in predicting the swelling behavior of different metals over a wide range of temperatures, dose rates, bombarding particles and irradiation time structures. Swelling of 316 stainless steel, Aluminum and Nickel bombarded with heavy ions, neutrons, and electrons at dose rates varying from 10−6 to 10−1 dpa/second is studied for both steady-state and pulsed irradiations.
TL;DR: In this article, the model of charge formation in collisions with single atoms was used for simulation of scattering on a damaged single crystal surface, where the orientational effects in charge state of scattered ions are due to different set of collision parameters along different scattering directions.
Abstract: Some computer calculations using the model of charge formation in collisions with single atoms were made for simulation of scattering on a damaged single crystal surface. The orientational effects in charge state of scattered ions are due to different set of collision parameters along different scattering directions.
TL;DR: In this paper, the electron yields from clean and oxydized Inconel 625 surfaces have been measured for H+, H+ 2, He+, O+ and Ar+ ions at normal incidence in the energy range 1.5-40 keV.
Abstract: Electron yields from clean and oxydized Inconel 625 surfaces have been measured for H+, H+ 2, He+,O+ and Ar+ ions at normal incidence in the energy range 1.5–40 keV. These measurements have been made under ultrahigh vacuum and the samples were freed of surface contaminants by bombarding with high doses of either 20 keV H+ 2 or 30 keV Ar+ ions. Differences in yields of oxydized versus clean surfaces are explained in terms of differences in the probability that electrons internally excited escape upon reaching the surface.
TL;DR: In this article, the morphological evolution of pyramids, developed on bombarded copper surfaces, as a function of consecutive doses of 12 keV Kr-ions from 2.4 × 1016 up to 3× 1016 ions/cm2, has been studied.
Abstract: The morphological evolution of pyramids, developed on bombarded copper surfaces, as a function of consecutive doses of 12 keV Kr—ions from 2.4 × 1016 up to 3 × 1016 ions/cm2, has been studied. In disagreement with many previous studies, apparently based on a limited choice of doses which were sometimes not in sequence, we found that the pyramids disappeared at high enough doses. Pyramids are therefore not an equilibrium structure.
TL;DR: In this article, the changes in the glow curve shape of CaSO4: Dy phosphor induced by gamma radiation in dose region 0.1 Gy-2.6 × 105 Gy were studied.
Abstract: The changes in the glow curve shape of CaSO4: Dy phosphor induced by gamma radiation in dose region 0.1 Gy-2.6 × 105 Gy were studied. With increase in gamma dose, initially, the glow curve shows a rapid increase in its peak width followed by its decrease with subsequent increase in gamma dose. This variation in peak width has been found to be due to the rapid growth and shift (towards lower temperatures) of a shoulder located at about 340°C for low doses. The shift and growth of the shoulder has been explained by preferential filling, first, of deeper trap components followed by filling of shallower trap components. In addition, for doses above 2 Gy, a high temperature peak distribution, peaking around 420°C, is noted.
TL;DR: In this article, a plan and 90° cross-sectional GaAs slices were implanted with 450 keV Se+ ions with the slices at 200°C, and two different types of damage occurred.
Abstract: (100) GaAs slices were implanted with 450 keV Se+ ions with the slices at 200°C. Ion doses of 1013, 1014, 5 × 1014 and 1015 cm−2 were used, and the specimens subsequently annealed at 400,500,600,700 and 800°C using A1 as an encapsulant. TEM studies of the damage were made using “plan” and “90° cross-sectional” specimens. Two different types of damage occurred. “Surface” damage extended from the surface to a depth of ∼600 A, and consisted of fine irregular structure at low annealing temperatures and dislocation lines at high annealing temperatures. “Interior” damage occurred in bands beneath the surface at doses of 1014 cm−2 and greater, and consisted of clusters at low annealing temperatures and dislocation loops at high annealing temperatures. In some instances the “interior” damage was present in two discrete bands. The damage often extended to depths of 3 to 4 times the LSS range, and the formation of damage observable by TEM was often retarded when the implanted ion concentration was high.
TL;DR: In this paper, a simulation of the reflection of a 30 KeV Ar+ ion beam from a (100) copper single crystal is carried out under the semichannel condition, using the binary collision model, and the main features of the spatial distributions of reflected ions are well explained by Yurasova's arguments.
Abstract: Computer simulation of the reflection of a 30 KeV Ar+ ion beam from a (100) copper single crystal is carried out under the semichannel condition, using the binary collision model. The present results have shown that the main features of the spatial distributions of reflected ions are well explained by the Yurasova's arguments. It is also found that the Parilis's spot A and spot B contribute appreciably to the spatial distribution at small incident angles. The relation between the semichanneling effect and the planar or axial channeling effect is also discussed in detail.
TL;DR: In this paper, the authors measured the concentration of mixed dumbbells as a function of irradiation fluence in crystals of Al-0.10 at.% Ag, Cu- 0.25 at.%.
Abstract: Channeling techniques were used to measure the concentration of mixed dumbbells as a function of irradiation fluence in crystals of Al-0.10 at.% Ag, Cu-0.25 at.% Be and Mg-0.18 at.% Ag. From the experimentally observed production rates of mixed dumbbells from alpha or deuteron irradiations at temperatures where self-interstitials were mobile, it was concluded that the dominant trapping configuration was the mixed dumbbell. In the case of the AI-0.10 at.% Ag alloy, mixed dumbbell trapping dominated at irradiation temperatures of both 70 and 150 K. The ratio of trapping efficiency ev , of vacancies for interstitials to the trapping efficiency ed of solute atoms for interstitials was ev/ed = 5 ± 2 in all cases.
TL;DR: In this paper, a discussion of electrostatic scanning systems with respect to mechanical scanning, uniformity and current capabilities as they relate to ion implanters is given with regards to the degradation of uniformity due to wafer tilt.
Abstract: A discussion of electrostatic scanning systems is given with respect to mechanical scanning, uniformity and current capabilities as they relate to ion implanters. Equations for the degradation of uniformity due to wafer tilt. misalignment and changing beam size are presented. Some commercial implantation scanning systems and related data are also presented along with a proposed high current electrostatic scanning system.
TL;DR: In this paper, a finite number of generations of helium blistering on austenite steel and Cr-Ni alloy was investigated at ion energy 40 and 100 keV and at doses from 3.1018 cm−2 to 1020 cm −2.
Abstract: The helium blistering on austenite steel and Cr-Ni alloy was investigated at ion energy 40 and 100 keV and at doses from 3. 1018 cm−2 to 1020 cm−2. A finite number of blister generations depending on ion-energy is observed. The diameter of blisters decreases from generation to generation and after the last generation of blisters the increase of doses results in sputtering of the surface and in formation of porous structure of the surface. Theoretical analysis shows: (i) blisters of subsequent generations can be formed only on places where blister covers of previous generations are opened; (ii) The blister diameter decreases from one generation to the next. Hence only a finite number of blister generations can be formed on a given surface. The number of possible blister generations is estimated as a function of ion energy.
TL;DR: In this article, the paths of the charge movements between the complex defect aggregates which exist within the LiF: Mg: Ti suggest that the simple classical analysis may be inappropriate and whilst one predicts the same curve shapes the measured parameters are Sx and xE. where 1 ≤ x ≤ 2.
Abstract: Previous analyses of the high temperature glow peaks in LiF (TLD 100) have suggested that the peaks may be described by classical “first order” kinetics for the thermoluminescence. However. the pre-exponential factor S and activation energy E are anomalously high (e.g., for peak 5, E ∼ 2.06 eV, and S ∼ 5 × 1020 s−l). A reappraisal of the paths of the charge movements between the complex defect aggregates which exist within the LiF: Mg: Ti suggests that the simple classical analysis may be inappropriate and whilst one predicts the same curve shapes the measured parameters are Sx and xE. where 1 ≤ x ≤ 2. Hence the energy required for the primary step of charge release is quite normal for the temperature range at which the glow peaks are observed (e.g., S ∼ 1011 s−l, E ∼ 1 eV, Tmax ∼ 200°C). The apparent difference between glow curve values of E and S and those from isochronal anneals are satisfactorily explained and the two methods are seen to be in agreement.
TL;DR: In this article, a model of a possible model of exciton states which are perturbed after exciton diffusion to imperfections is discussed in terms of a possibly perturbed exciton state model.
Abstract: Luminescence from a wide range of NaCl crystals of different purity has been excited by electrons and ion beams. Despite the range of crystal quality there are many similarities between the spectra excited under similar conditions. At both 77 and 300 K there is strong emission near 2.4 eV in all samples but the so called “intrinsic π emission” near 3.4 eV is sensitive in position to the source of the crystals and is readily suppressed by the presence of imperfections. In the energy range between 2.4 and 3.4 eV many component features can be detected. These are most easily resolved in the impure samples. The form of the spectra is sensitive to the total irradiation dose, dose rate and lifetime-resolved components. The reasons for the changes are briefly discussed in terms of a possible model of exciton states which are perturbed after exciton diffusion to imperfections.