Study of Near Surface Structure and Composition for High Dose Implantation of Cr+ into Si

1983 ◽  
Vol 27 ◽  
Author(s):  
F. Namavar ◽  
J. I. Budnick ◽  
H. C. Hayden ◽  
F. A. Otter ◽  
V. Patarini
Keyword(s):  
Dose Rate ◽  
Surface Composition ◽  
High Vacuum ◽  
Target Chamber ◽  
Fixed Dose ◽  
Compositional Variation ◽  
High Dose ◽  
Rutherford Back Scattering ◽  
Near Surface ◽  
Dose Rates

ABSTRACTThe dependence of the implanted layer composition on total dose, dose rate and target chamber environment for Cr+ implanted Si have been studied by means of Rutherford Back Scattering (RBS) and Auger Electron Spectroscopy (AES). Implantation of Cr+ for doses up to 2 × 1018 ions/cm2 and a fixed dose rate and energy were carried out in an ultra high vacuum (UHV) system as well as in a diffusion pumped vacuum (DPV) system. For the former, the maximum Cr concentration was about 42%. On the other hand, implantation of Cr in a DPV system resulted in a much higher peak concentration (86%) and retention.Both the RBS and AES results positively demonstrate the existence of extensive surface carbon for a Si-rich surface and a chromium oxide layer for the Cr-rich surface. This result suggests that the interaction of oxygen or carbon occurs preferentially and depends on the surface composition.No surface compositional variation could be observed by the RBS experiments for Cr implanted in a UHV system for different dose rates. In contrast, for implantation in a DPV system, higher concentrations can be achieved for lower dose rates.

The Influence of Implantation Conditions and Target Orientation in High Dose Implantation of Al+ into Si

1983 ◽  
Vol 27 ◽  
Author(s):  
F. Nam-Avar ◽  
J. I. Budnick ◽  
A. Fasihuddin ◽  
H. C. Hayden ◽  
D. A. Pease ◽  
...  
Keyword(s):  
Dose Rate ◽  
Surface Composition ◽  
High Vacuum ◽  
High Dose Rate ◽  
Ultra High Vacuum ◽  
High Dose ◽  
Polycrystalline Structure ◽  
Rutherford Back Scattering ◽  
Near Surface ◽  
Projected Range

ABSTRACTWe report the preliminary results of a study to determine the dependence of the near surface composition and structure on total dose, dose rate, vacuum condition and substrate orientation for Al implantation into Si (111) and Si (100) with doses up to 2 × 10l8 ions/cm2. Our studies include the results of Rutherford Back Scattering (RBS), Auger Electron Spectroscopy (AES) and x-ray diffraction measurements on samples implanted with a 100 keV energy in a diffusion pumped vacuum (DPV) system (10−6 Torr) with and without a LN2 trap and in an ultra high vacuum (UHV) system (2–4) x 10−8 Torr.Results of high dose rate (50 μA/cm2 ) implantation into Si (111) in an untrapped DPV system indicate that Al segregates with a preferred (111) orientation. For a dose of 1 × 1018 ions/cm2 the surface is Al-rich to a depth of 2500Å while for lower doses the surface is silicon-rich. A carbon build-yp occurred for samples prepared by low dose rate (5 μA/cm2 ) implantation. However, no Al segregation could be observed for doses of less than 1018 ions/cm2 . A similar behavior has been observed for Si (100) except that Al segregation occurs with a polycrystalline structure. Moreover, the segregated Al is present at depths greater than the projected range.When implantation was carried out in a DPV system with a LN2 trap, no carbon peaks could be observed by RBS regardless of the dose rate. For these conditions, as well as for the implantation of Al in an UHV system, we find Al segregation with a polycrystalline structure independent of the dose rates and target orientations we used. Al is observed at a depth greater by a factor of two than the expected value from the Rpcalculations. The Al depth penetration increases with the dose of implantation.

scholarly journals Surface composition and near-surface hardness studies on high dose boron-implanted 304 stainless steel

1990 ◽  
Vol 13 (5) ◽  
pp. 333-342 ◽  
Author(s):  
A K Goel ◽  
N D Sharma ◽  
R K Mohindra ◽  
P K Ghosh ◽  
M C Bhatnagar
Keyword(s):  
Stainless Steel ◽  
Surface Composition ◽  
Surface Hardness ◽  
304 Stainless Steel ◽  
High Dose ◽  
Near Surface

The effects of high dose rates of ionizing radiations on solutions of iron and cerium salts

1960 ◽  
Vol 255 (1283) ◽  
pp. 490-508 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Dose Rate ◽  
Ferrous Sulphate ◽  
High Dose ◽  
Oh Radicals ◽  
Dose Rates ◽  
Reaction Zones ◽  
Constant Dose ◽  
Ceric Sulphate ◽  
Ionizing Radiations

The electron beam generated by a 15 MeV linear accelerator has been employed to induce reactions in aerated aqueous solutions of 1 to 25 mM ferrous sulphate, and of 0⋅1 to 1 mM ceric sulphate. The radiation was delivered in pulses of 1⋅3 μ s duration and over a range of dose rates from 0⋅5 to 20000 rads/pulse. Radiation yields at constant dose rate were compared with the aid of a chemical dose monitor. A system of two thin, widely spaced, irradiation vessels was employed to determine the variation of yield of any one system over successive known ranges of dose rate. The yield of ferric sulphate in the iron system was found to decrease with increasing dose rate in the range 0⋅01 to 10 krads/pulse by an overall factor of 0⋅85, and was appreciably dependent on the initial concentrations of dissolved oxygen and of ferrous sulphate at high dose rates. Yields of hydrogen and of hydrogen peroxide were practically independent of dose rate. The observations have been interpreted on the basis of inter-radical reactions which occur when the reaction zones of neighbouring clusters overlap. The following reactions can account for all the data: OH + Fe 2+ → Fe 3+ + OH ¯ , (1) H + O 2 → HO 2 , (2) H + OH → H 2 O. (7) The values k 1 / k 7 = 0⋅0062, and k 2 / k 7 = 0⋅22 are reasonably consistent with the observations. In the ceric sulphate system the yield of cerous sulphate increases progressively over the range 0⋅01 to 10 krads/pulse by an overall factor of 1⋅4. The data accord with the view that at high dose rates OH radicals react with them selves ultimately to form hydrogen peroxide, in competition with their normal reaction with cerous sulphate.

scholarly journals Fractionated versus single-dose total body irradiation at low and high dose rates to condition canine littermates for DLA-identical marrow grafts

Blood ◽  
1994 ◽  
Vol 83 (11) ◽  
pp. 3384-3389 ◽  
Author(s):  
R Storb ◽  
RF Raff ◽  
FR Appelbaum ◽  
HJ Deeg ◽  
TC Graham ◽  
...  
Keyword(s):  
Dna Repair ◽  
Single Dose ◽  
Dose Rate ◽  
Total Body Irradiation ◽  
High Dose Rate ◽  
Lymphoid Cells ◽  
High Dose ◽  
Dose Rates ◽  
Total Body ◽  
Allogeneic Marrow

Abstract We explored in dogs the immunosuppressive properties of 450 cGy total body irradiation (TBI) delivered from two opposing 60Co sources, as assessed by the criterion of successful engraftment of allogeneic genotypically DLA-identical littermate marrow. Two questions were asked in this study. Firstly, does dose rate affect the immunosuppressive effect of TBI when administered in a single dose? Secondly, does fractionation alter the immunosuppression of TBI when delivered at a very fast dose rate? Dose rates studied included 7 and 70 cGy/min, and fractionation involved four fractions of 112.5 cGy each, with 6-hour minimum interfraction intervals. Six of 7 dogs receiving 450 cGy single- dose TBI at 70 cGy/min showed sustained engraftment of the allogeneic marrow, compared with 1 of 7 dogs receiving single-dose TBI at 7 cGy/min (P = .01). Fractionated TBI at 70 cGy/min resulted in sustained allogeneic engraftment in 3 of 10 dogs, a result that was statistically significantly worse than that with single-dose TBI at 70 cGy/min (P = .03) and not statistically different (P = .24) from that with fractionated TBI delivered at 7 cGy/min (0 of 5 dogs engrafted). A single dose of 450 cGy of TBI delivered at a rate of 70 cGy/min is significantly more immunosuppressive than the same total dose delivered at 7 cGy/min. Fractionated TBI at 70 cGy/min is significantly less immunosuppressive than single-dose TBI at 70 cGy/min and not significantly different from fractionated TBI administered at 7 cGy/min. Results are consistent with the notion that significant DNA repair in lymphoid cells is possible during interfraction intervals at the relatively high dose rate of 70 cGy/min.

Electron and Beta Dose Rates of UO2 Pellet and Fuel Rod

2013 ◽  
Author(s):  
Guoqing Zhang ◽  
Xuexin Wang ◽  
Jiangang Zhang ◽  
Dajie Zhuang ◽  
Chaoduan Li ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Dose Rate ◽  
Radiation Protection ◽  
High Dose Rate ◽  
High Dose ◽  
Electron Dose ◽  
Dose Rates ◽  
Fuel Rod ◽  
Calculation Results ◽  
Beta Dose

The isotopes of uranium and their daughter nuclides inside the UO2 pellet emit mono-energetic electrons and beta rays, which generate rather high dose rate near the UO2 pellet and could cause exposure to workers. In this work calculations of electron dose rates have been carried out with Monte Carlo codes, MCNPX and Geant4, for a UO2 pellet and a fuel rod. Comparisons between calculations and measurements have been carried out to verify the calculation results. The results could be used to estimate the dose produced by electrons and beta rays, which could be used to make optimization for radiation protection purpose.

The radiation chemistry of carbon monoxide at very high dose rates

1970 ◽  
Vol 48 (19) ◽  
pp. 3029-3033 ◽  
Author(s):  
C. Willis ◽  
O. A. Miller
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Excited State ◽  
Oxygen Atom ◽  
Dose Rate ◽  
Electron Accelerator ◽  
Radiation Chemistry ◽  
High Dose ◽  
Dose Rates ◽  
Very High

Carbon monoxide has been irradiated with single intense pulses from an electron accelerator at a dose rate of ~ 2 × 1027 eV g−1 s−1. The yield of carbon dioxide obtained was G(CO2) = 0.7 ± 0.1 with a very small yield of carbon suboxide, G(C3O2) ≤ 0.02.Addition of propene reduces the carbon dioxide yield to almost zero while addition of propane has no effect. This suggests that propene is acting as an oxygen atom scavenger rather than as a quencher of an excited state of carbon monoxide. However, rate constant data do not support this suggestion and it is concluded that the residual yield of carbon dioxide observed at high dose rates arises from reaction 9[Formula: see text]where CO+ is in an A2Π or B2Σ+ state.

On the Amorphization of Silicon by Light Ion Implantation: Ion Flux and Substrate Temperature Effects

1990 ◽  
Vol 201 ◽  
Author(s):  
A. Claverie ◽  
A. Roumili ◽  
N. Gessinn ◽  
J. Beauvillain
Keyword(s):  
Electron Microscopy ◽  
Ion Implantation ◽  
Substrate Temperature ◽  
Dose Rate ◽  
Energy Calculation ◽  
Apparent Contradiction ◽  
Near Surface ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects

AbstractIn this work, we have observed by cross-sectional electron microscopy (XTEM) and high resolution electron microscopy (HREM) the kinetics of silicon amorphization during nitrogen and helium bombardments for various dose rates and substrate temperatures. It is shown that the progression of the cla interfaces can be accurately described by the “Critical Damage Energy Density” (CDED) model for both ions at 100°K. At this temperature however, dose rate effects are unimportant. When increasing the substrate temperature up to 300°K, the amorphization efficiency is lowered. At 300°K dose rate effects are important and we show that for higher dose rates, the efficiency of the amorphization process is improved. In this case, the amorphous layers created by helium implantation are situated in the near surface region in apparent contradiction with damage calculations. The present experimental study demonstrates the competition which exists between the generation rate of point defects and the anihilation rate of these defects. Therefore, it is shown that the position of the a-layers created by light ion implantation at room temperature can be predicted by using a three-dimensional damage energy calculation.

scholarly journals Chernobyl-level radiation exposure damages bumblebee reproduction: a laboratory experiment

2020 ◽  
Vol 287 (1937) ◽  
pp. 20201638
Author(s):  
Katherine E. Raines ◽  
Penelope R. Whitehorn ◽  
David Copplestone ◽  
Matthew C. Tinsley
Keyword(s):  
Radiation Dose ◽  
Radiation Exposure ◽  
Dose Rate ◽  
Colony Growth ◽  
High Dose ◽  
Radiological Protection ◽  
Negative Consequences ◽  
Exclusion Zone ◽  
Radiation Dose Rate ◽  
Dose Rates

The consequences for wildlife of living in radiologically contaminated environments are uncertain. Previous laboratory studies suggest insects are relatively radiation-resistant; however, some field studies from the Chernobyl Exclusion Zone report severe adverse effects at substantially lower radiation dose rates than expected. Here, we present the first laboratory investigation to study how environmentally relevant radiation exposure affects bumblebee life history, assessing the shape of the relationship between radiation exposure and fitness loss. Dose rates comparable to the Chernobyl Exclusion Zone (50–400 µGy h −1 ) impaired bumblebee reproduction and delayed colony growth but did not affect colony weight or longevity. Our best-fitting model for the effect of radiation dose rate on colony queen production had a strongly nonlinear concave relationship: exposure to only 100 µGy h −1 impaired reproduction by 30–45%, while further dose rate increases caused more modest additional reproductive impairment. Our data indicate that the practice of estimating effects of environmentally relevant low-dose rate exposure by extrapolating from high-dose rates may have considerably underestimated the effects of radiation. If our data can be generalized, they suggest insects suffer significant negative consequences at dose rates previously thought safe; we therefore advocate relevant revisions to the international framework for radiological protection of the environment.

High Dose Rate Oxygen Implantation for Formation of Silicon-on-Insulator Structures

1990 ◽  
Vol 201 ◽  
Author(s):  
E. Cortesi ◽  
F. Namavar ◽  
R. F. Pinizzotto ◽  
H. Yang
Keyword(s):  
Dose Rate ◽  
Silicon Surface ◽  
High Dose Rate ◽  
Silicon On Insulator ◽  
High Dose ◽  
Surface Oxide Layer ◽  
Dose Rates ◽  
Pit Formation ◽  
Lower Dose Rate ◽  
Very High

AbstractWe have studied Separation by IMplantation of OXygen (SIMOX) processes using very high dose rates (40–60 μA/cm2). For a dose of 4 × 1017 O+/cm2 at 160 keV, the structure formed by implantation at 50 μA/cm2 is very similar to that associated with lower dose rates. The same dose implanted at a dose rate of 60 μA/cm2, however, results in the formation of pits in the silicon surface as well as a somewhat different oxide structure. Implantation through a surface oxide layer appears to result in a structure similar to that associated with lower dose rate implantation. These and higher dose samples suggest that the threshold for pit formation is related to both dose rate and dose.

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