The Microstructure of Xe Implanted GaAs

1975 ◽  
Vol 33 ◽  
pp. 258-259
Author(s):  
C. R. Hills ◽  
G. J. Thomas ◽  
H. J. Stein
Keyword(s):  
Ion Implantation ◽  
Dose Rate ◽  
Room Temperature ◽  
Low Dose ◽  
Important Variable ◽  
Transmission Microscopy ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects ◽  
Ion Backscattering

Previous investigators have shown that the surface regions of GaAs samples implanted at room temperature with 40-100 keV Ne ions become amorphous after a dose of the order of 1x1014ions cm-2. Their study also indicated that implantation above room temperature (35°-200°C) results in the retention of crystallinity even with fluences two to three orders of magnitude higher. Investigators using ion backscattering and optical absorption have shown that ion dose rate is also an important variable in ion implantation. In the present investigation, transmission microscopy has been used to further study the temperature and dose rate effects of ion implantation in GaAs. A number of {111} and {l00} single crystal GaAs samples have been implanted with 275 keV Xe ions to doses of 1015 and 1016 ions cm-2 at dose rates ranging from 2.5x1012 to 8.1xl012ions cm-2 sec-1.Low dose (1015ions cm-2) implantations at room temperature produced amorphous layers at all dose rates.

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.

Dose-Rate Effects of Protons and Light Ions for DNA Damage Induction, Survival and Transformation in Apparently Normal Primary Human Fibroblasts

2021 ◽  
Author(s):  
Paula V. Bennett ◽  
Alicia M. Johnson ◽  
Sarah E. Ackerman ◽  
Pankaj Chaudhary ◽  
Deborah J. Keszenman ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Survival ◽  
Dose Rate ◽  
Low Dose ◽  
Human Fibroblasts ◽  
Dose Rates ◽  
In Vitro Transformation ◽  
Dose Rate Effects ◽  
Rate Effects

We report on effects of low-dose exposures of accelerated protons delivered at high-dose rate (HDR) or a simulated solar-particle event (SPE) like low-dose rate (LDR) on immediate DNA damage induction and processing, survival and in vitro transformation of low passage NFF28 apparently normal primary human fibroblasts. Cultures were exposed to 50, 100 and 1,000 MeV monoenergetic protons in the Bragg entrance/plateau region and cesium-137 γ rays at 20 Gy/h (HDR) or 1 Gy/h (LDR). DNA double-strand breaks (DSB) and clustered DNA damages (containing oxypurines and abasic sites) were measured using transverse alternating gel electrophoresis (TAFE) and immunocytochemical detection/scoring of colocalized γ-H2AX pS139/53BP1 foci, with their induction being linear energy transfer (LET) dependent and dose-rate sparing observed for the different damage classes. Relative biological effectiveness (RBE) values for cell survival after proton irradiation at both dose-rates ranged from 0.61–0.73. Transformation RBE values were dose-rate dependent, ranging from ∼1.8–3.1 and ∼0.6–1.0 at low doses (≤30 cGy) for HDR and LDR irradiations, respectively. However peak transformation frequencies were significantly higher (1.3–7.3-fold) for higher doses of 0.5–1 Gy delivered at SPE-like LDR. Cell survival and transformation frequencies measured after low-dose 500 MeV/n He-4, 290 MeV/n C-12 and 600 MeV/n Si-28 ion irradiations also showed an inverse dose-rate effect for transformation at SPE-like LDR. This work demonstrates the existence of inverse dose-rate effects for proton and light-ion-induced postirradiation cell survival and in vitro transformation for space mission-relevant doses and dose rates.

scholarly journals Investigation of dose-rate effects and cell-cycle distribution under protracted exposure to ionizing radiation for various dose-rates

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Yusuke Matsuya ◽  
Stephen J. McMahon ◽  
Kaori Tsutsumi ◽  
Kohei Sasaki ◽  
Go Okuyama ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Ionizing Radiation ◽  
Dose Rate ◽  
Cell Cycle Distribution ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects

Dose-Rate Effects for Various Dose Rates of252Cf Radiation on HeLa Cells in Culture

Radiology ◽  
1970 ◽  
Vol 96 (1) ◽  
pp. 171-174 ◽  
Author(s):  
R. G. Fairchild ◽  
R. M. Drew ◽  
H. L. Atkins
Keyword(s):  
Dose Rate ◽  
Hela Cells ◽  
Dose Rates ◽  
Cells In Culture ◽  
Dose Rate Effects ◽  
Rate Effects

Dose and Dose-Rate Effects of Low-Dose Ionizing Radiation on Activation of Trp53 in Immortalized Murine Cells

2004 ◽  
Vol 162 (3) ◽  
pp. 296-307 ◽  
Author(s):  
Takashi Sugihara ◽  
Junji Magae ◽  
Renu Wadhwa ◽  
Sunil C. Kaul ◽  
Yasushi Kawakami ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Dose Rate ◽  
Low Dose ◽  
Dose Rate Effects ◽  
Rate Effects

Radiation protection in irradiated dimethylsiloxane polymers

1963 ◽  
Vol 273 (1352) ◽  
pp. 117-132 ◽  
Keyword(s):  
Protective Effect ◽  
Dose Rate ◽  
Reaction Mechanisms ◽  
Radical Reactions ◽  
Gas Evolution ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects ◽  
Colloidal Sulphur ◽  
Dose Rate Effect

Small concentrations of certain additives can greatly modify the effects produced by radiation of macromolecules such as polymers and biological systems. Various mechanisms of protection can be envisaged, and these lead to different kinetics in protection effects. Most published work studies the elimination of the additive, rather than the change in the macromolecule. In previous papers in this series, the dose rate effects expected for radical reactions were observed for anthracene solutions in hexane and cyclohexane. With anthracene in dimethylsiloxane polymers, however, no such dependence was observed. This problem is studied in greater detail in the present paper. The additives studied were anthracene, iodine, sulphur and benzophenone, and their protective effect on the crosslinking of dimethylsiloxane polymer was investigated a t various dose rates. Contrary to generally accepted views on reaction mechanisms no dose-rate effect was observed; anthracene provided no protection against crosslinking, although it was itself destroyed. Iodine and colloidal sulphur provided a considerable measure of protection, but had no effect on gas evolution. Benzophenone also offered protection, but also reduced the gas yield. To explain these very different patterns of behaviour, it is necessary to modify some present views on the nature of the protection offered; this leads to a discussion as to the mechanism of crosslinking.

scholarly journals Damage Nucleation in Si During Ion Irradiation

1984 ◽  
Vol 41 ◽  
Author(s):  
O. W. Holland ◽  
D. Fathy ◽  
J. Narayan
Keyword(s):  
Dose Rate ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Liquid Nitrogen Temperature ◽  
Mass Dependence ◽  
Dose Rate Effects ◽  
Rate Effects ◽  
Temperature Irradiation ◽  
Nucleation Mechanisms ◽  
Accumulation Of Damage

AbstractDamage nucleation in single crystals of silicon during ion irradiation is investigated. Experimental results and mechanisms for damage nucleation during both room and liquid nitrogen temperature irradiation with different mass ions are discussed. It is shown that the accumulation of damage during room temperature irradiation depends on the rate of implantation. These dose rate effects are found to decrease in magnitude as the mass of the ions is increased. The significance of dose rate effects and their mass dependence on nucleation mechanisms is discussed.

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