Growth of Vacancy Clusters During Post-Irradiation Annealing of Ion Implanted Silicon,

1995 ◽  
Vol 396 ◽  
Author(s):  
A. van Veen ◽  
H. Schut ◽  
A. Rivera ◽  
A.V. Fedorov
Keyword(s):  
Cavity Growth ◽  
Positron Beam ◽  
Vacancy Cluster ◽  
High Dose ◽  
High Concentration ◽  
Vacancy Clusters ◽  
Dissociation Energies ◽  
Beam Analysis ◽  
Growth Barriers ◽  
Silicon Based

AbstractAnnealing experiments of deuterium implanted silicon have been performed while positron beam analysis was used for monitoring the cavity growth. The experiments indicate up to annealing temperature 500° C similar defect evolution for both the low dose of 1016 cm-2 as for a 3 times higher dose. At this temperature the deuterium stabilized vacancy clusters dissociate and only in the case of the high dose micro-cavities are formed. Monte Carlo simulations of vacancy cluster growth in silicon based on vacancy cluster dissociation energies, calculated with the Stillinger Weber potential, have been performed. The results indicate that for low initial defect concentrations vacancy clusters might be hindered to grow because the vacancy binding energy of the clusters does not increase monotonically with the cluster size. Only a high concentration guarantees that growth barriers will be overcome.

Impact of Hydrogen Implantation on Helium Implantation Induced Defects

2005 ◽  
Vol 108-109 ◽  
pp. 309-314 ◽  
Author(s):  
G. Gaudin ◽  
Frédéric Cayrel ◽  
Corrado Bongiorno ◽  
Robert Jérisian ◽  
Vito Raineri ◽  
...  
Keyword(s):  
Cavity Growth ◽  
High Dose ◽  
Defect Band ◽  
Hydrogen Addition ◽  
Recent Developments ◽  
Hydrogen Implantation ◽  
Helium Implantation ◽  
Silicon Based ◽  
Induced Defects ◽  
The Impact

Silicon-based power device performances are largely affected by metal contamination occurring during device manufacturing. Among the usual gettering techniques, recent developments were done on high dose helium implantation. Even though the gettering efficiency of this technique has been demonstrated in device application, the required doses are still extremely high for an industrial application. Recently, it has been shown that the use of H/He co-implantation limits the total requested doses [1]. In this paper, co-implantation of H/He, which has been already used to reduce the dose in the smart-cut® process is explored. The goal of this work is to decrease efficiently the implanted dose maintaining an efficient metallic gettering without degrading the Si surface. The impact of H implantation on He implantation induced defects is carefully studied. The TEM observations have evidenced that hydrogen addition drastically modified the defect band structure and promotes the cavity growth.. Additionally, we demonstrate that an efficient gettering can be obtained.

The Study of Si, Se and O-Implanted GaAs by Slow Positrons

1992 ◽  
Vol 262 ◽  
Author(s):  
S. Fujii ◽  
S. Shikata ◽  
L. Wei ◽  
S. Tanigaw
Keyword(s):  
Positron Beam ◽  
Annealed Specimen ◽  
Electrical Characteristics ◽  
High Concentration ◽  
Positron Energy ◽  
Vacancy Clusters ◽  
Activation Efficiency ◽  
Before And After ◽  
Parallel Measurement ◽  
Variable Energy

ABSTRACTVariable-energy (0–30keV) positron beam studies have been carried out on 200 keV Se-implanted and 70 keV Si-implanted GaAs specimens before and after annealing for electrical activation. From the measurements of Doppler broadened profiles as a function of incident positron energy, it was found that vacancy clusters with high concentration were introduced in the annealed specimen after Se implantation. From the parallel measurement of electrical characteristics, a higher activation efficiency was found for the higher concentration of vacancy clusters. That fact implies that electrons supplied by the activation of Se also convert the charge state of As vacancies from positive to negative. In contrast, no vacancy clusters were introduced in the Si-implanted GaAs. On the other hand, oxygen clustering was found in annealed specimen after O implantation.

Helium and Hydrogen Induced Growth of Microcavities in Silicon; Application to Gas And Impurity Collection

1994 ◽  
Vol 373 ◽  
Author(s):  
A. Van Veen ◽  
H. Schut ◽  
R.A. Hakvoort ◽  
A. Fedorov ◽  
K.T. Westerduin
Keyword(s):  
Thermal Stability ◽  
Room Temperature ◽  
Positron Beam ◽  
Experimental Results ◽  
Subsequent Annealing ◽  
Sharp Threshold ◽  
Vacancy Clusters ◽  
Beam Analysis ◽  
Atomistic Calculations ◽  
Thermal Stability Of

AbstractThermal helium desorption spectrometry and positron beam analysis have been used to monitor the growth of helium vacancy clusters during room temperature helium irradiation of silicon and during subsequent annealing to 1300 K. Experimental results obtained with hydrogen irradiation show that also hydrogen can be used to create cavities. There is a rather sharp threshold dose for creating cavities that will survive 1300 K annealing. It appears that positrons form a sensitive probe for the trapping and release of impurities inside the cavities. Results of atomistic calculations are used to discuss thermal stability of helium vacancy complexes. The results are related to recent impurity gettering studies based on impurity trapping at helium induced gettering centers.

Multiscale Modeling of Helium-Vacancy Cluster Nucleation under Irradiation: A Kinetic Monte-Carlo Approach

2009 ◽  
Vol 1215 ◽  
Author(s):  
Tomoaki Suzudo ◽  
Masatake Yamaguchi ◽  
Hideo Kaburaki ◽  
Ken-ichi Ebihara
Keyword(s):  
Monte Carlo ◽  
Ab Initio ◽  
Point Defects ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Model ◽  
Vacancy Cluster ◽  
Austenitic Steels ◽  
Vacancy Clusters ◽  
Dissociation Energies ◽  
Object Kinetic Monte Carlo

AbstractWe applied ab initio calculation and an object kinetic Monte Carlo modeling to the study of He-vacancy cluster nucleation under irradiation in bcc and fcc Fe, which are surrogate materials for ferritic/martensitic and austenitic steels, respectively. The ab initio calculations provided parameters for the object kinetic Monte Carlo model, such as the migration energies of point defects and the dissociation energies of He and vacancy to He-vacancy clusters. We specially focused on the simulation of high He/dpa irradiation such as He-implantation into the materials and tracked the nucleation of clusters and the fate of point defects such as SIAs, vacancies, and He atoms. We found no major difference of He-vacancy cluster nucleation between bcc and fcc Fe when we ignore the intracascade clustering even if the migration energies of point defects are significantly different between the two crystals.

Calibration Method for Elemental Quantification

2000 ◽  
Vol 6 (S2) ◽  
pp. 536-537
Author(s):  
C. B. Vartuli ◽  
F. A. Stevie ◽  
L. A. Giannuzzi ◽  
T. L. Shofner ◽  
B. M. Purcell ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Peak Concentration ◽  
Energy Dispersive Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Rutherford Backscattering Spectrometry ◽  
Calibration Method ◽  
High Dose ◽  
High Concentration ◽  
Borophosphosilicate Glass ◽  
Secondary Ion

Energy Dispersive Spectrometry (EDS) is generally calibrated for quantification using elemental standards. This can introduce errors when quantifying non-elemental samples and does not provide an accurate detection limit. In addition, variations between analysis tools can lead to values that differ considerably, especially for trace elements. By creating a standard with an exact trace composition, many of the errors inherent in EDS quantification measurements can be eliminated.The standards are created by high dose ion implantation. For ions implanted into silicon, a dose of 1E16 cm-2 results in a peak concentration of approximately 1E21 cm-3 or 2% atomic. The exact concentration can be determined using other methods, such as Rutherford Backscattering Spectrometry (RBS) or Secondary Ion Mass Spectrometry (SIMS). For this study, SIMS analyses were made using a CAMECA IMS-6f magnetic sector. Measurement protocols were used that were developed for high concentration measurements, such as B and P in borophosphosilicate glass (BPSG).

Does coffee, tea and caffeine consumption reduce the risk of incident breast cancer? A systematic review and network meta-analysis

2021 ◽  
pp. 1-13
Author(s):  
Shu Wang ◽  
Xiang Li ◽  
Yue Yang ◽  
Jingping Xie ◽  
Mingyue Liu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Systematic Review ◽  
Postmenopausal Women ◽  
Meta Analysis ◽  
High Dose ◽  
Dependent Manner ◽  
Tea Consumption ◽  
Case Control Studies ◽  
High Concentration ◽  
Coffee Intake

Abstract Objective: We aimed to evaluate the association between coffee and/or tea consumption and breast cancer (BC) risk among premenopausal and postmenopausal women and to conduct a network meta-analysis. Design: Systematic review and network meta-analysis. Setting: We conducted a systematic review of electronic publications in the last 30 years to identify case–control studies or prospective cohort studies that evaluated the effects of coffee and tea intake. Results: Forty-five studies that included more than 3 323 288 participants were eligible for analysis. Network meta-analysis was performed to determine the effects of coffee and/or tea consumption on reducing BC risk in a dose-dependent manner and differences in coffee/tea type, menopause status, hormone receptor and the BMI in subgroup and meta-regression analyses. According to the first pairwise meta-analysis, low-dose coffee intake and high-dose tea intake may exhibit efficacy in preventing ER(estrogen receptor)− BC, particularly in postmenopausal women. Then, we performed another pairwise and network meta-analysis and determined that the recommended daily doses were 2–3 cups/d of coffee or ≥5 cups/d of tea, which contained a high concentration of caffeine, particularly in postmenopausal women. Conclusions: Coffee and tea consumption is not associated with a reduction in the overall BC risk in postmenopausal women and is associated with a potentially lower risk of ER− BC. And the highest recommended dose is 2–3 cups of coffee/d or ≥5 cups of tea/d. They are potentially useful dietary protectants for preventing BC.

scholarly journals Pharmacologic modulation of 5-fluorouracil by folinic acid and high-dose pyridoxine for treatment of patients with digestive tract carcinomas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David Machover ◽  
Wathek Almohamad ◽  
Vincent Castagné ◽  
Christophe Desterke ◽  
Léa Gomez ◽  
...  
Keyword(s):  
Folinic Acid ◽  
Digestive Tract ◽  
Vitamin B6 ◽  
Colorectal Adenocarcinoma ◽  
High Dose ◽  
High Concentration ◽  
Carcinoma Of The Esophagus ◽  
Pancreas Adenocarcinoma ◽  
The Impact ◽  
High Dose Vitamin

AbstractSupplementation of cancer cells exposed to 5-fluorouracil (FUra) and folinic acid (FA) with high concentration pyridoxal 5′-phosphate, the cofactor of vitamin B6, potentiates the cytotoxicity of FUra in a synergistic interaction mode. We report a pilot study in 13 patients with previously untreated advanced carcinoma of the digestive tract to assess the impact of high-dose pyridoxine (PN) on the antitumor activity of regimens comprising FUra and FA. Five patients had colorectal adenocarcinoma (CRC); 5 had pancreas adenocarcinoma (PC); and 3 had squamous cell carcinoma of the esophagus (EC). Patients with CRC and with PC received oxaliplatin, irinotecan, FUra and FA, and patients with EC had paclitaxel, carboplatin, FUra and FA. PN iv from 1000 to 3000 mg/day preceded each administration of FA and FUra. Eleven patients responded. Two patients with CRC attained CRs and 3 had PRs with reduction rates ≥ 78%. Two patients with PC attained CRs, and 2 had PRs with reduction rates ≥ 79%. Responders experienced disappearance of most metastases. Of 3 patients with EC, 2 attained CRs. Median time to attain a response was 3 months. Unexpected toxicity did not occur. Results suggest that high-dose vitamin B6 enhances antitumor potency of regimens comprising FUra and FA.

Positron Beam Analysis of Amorphous Silicon

1992 ◽  
Vol 105-110 ◽  
pp. 1391-1394 ◽  
Author(s):  
R.A. Hakvoort ◽  
S. Roorda ◽  
A. van Veen ◽  
M.J. van den Boogaard ◽  
F.J.M. Buters ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Positron Beam ◽  
Beam Analysis

scholarly journals The effects of IGF-I on bovine follicle development and IGFBP-2 expression are dose and stage dependent

Reproduction ◽  
2006 ◽  
Vol 131 (3) ◽  
pp. 515-523 ◽  
Author(s):  
Kirsty A Walters ◽  
John P Binnie ◽  
Bruce K Campbell ◽  
David G Armstrong ◽  
Evelyn E Telfer
Keyword(s):  
Growth Factor ◽  
Granulosa Cells ◽  
Size Range ◽  
Regulatory System ◽  
Follicular Development ◽  
High Dose ◽  
Insulin Like Growth Factor ◽  
High Concentration ◽  
Antral Follicles ◽  
Igf I

This study aimed to determine the effect of insulin-like growth factor-I (IGF-I) on early antral bovine follicular development, and the expression of insulin-like growth factor-binding protein-2 (IGFBP-2). Antral follicles separated into three different size groups were cultured for 6 days in medium supplemented with either a low (10 ng/ml) or high (1 μg/ml) dose of human recombinant IGF-I. Oestradiol production by follicles in all size ranges, cultured in the presence of the high concentration of IGF-I, significantly increased by day 6 (P < 0.05). Follicles in the smallest size range, 165–215 μm, cultured in a high dose of IGF-I, were found to be significantly increased in size (P < 0.01). Oocyte health of the largest follicles (281–380 μm) was significantly improved by the addition of IGF-I to the culture medium. mRNA expression of IGFBP-2 was decreased in the granulosa cells of follicles, size range 216–280 μm, cultured with a high dose of IGF-I (P < 0.05). Granulosa cells (P < 0.05) and oocytes (P < 0.01) of the largest follicles (281–380 μm) showed a decrease in IGFBP-2 expression (protein) when cultured in the control and low-IGF-I treatment groups. Therefore, the response of a bovine follicle to IGF-I is both dose and stage dependent. This work supports a role for IGF-I in modulating somatic and germ-cell maturation and development in early antral follicles. Furthermore, the inverse relationship between the level of IGF-I stimulation and IGFBP-2 expression suggests a local regulatory system modulating IGF-I availability.

Ion-implantation Generated Nanovoids in Si and MgO Monitored by High Resolution Positron Beam Analysis

2000 ◽  
Vol 647 ◽  
Author(s):  
S.W.H. Eijt ◽  
C.V. Falub ◽  
A. van Veen ◽  
H. Schut ◽  
P.E. Mijnarends ◽  
...  
Keyword(s):  
High Resolution ◽  
Ion Implantation ◽  
Average Energy ◽  
Internal Surface ◽  
Positron Beam ◽  
Initial Energy ◽  
Thin Layers ◽  
Beam Analysis ◽  
Width Reduction ◽  
Non Destructive

AbstractThe formation of nanovoids in Si(100) and MgO(100) by 3He ion implantation has been studied. Contrary to Si in which the voids are generally almost spherical, in MgO nearly perfectly rectangular nanosize voids are created. Recently, the 2D-ACAR setup at the Delft Positron Research Center has been coupled to the intense reactor-based variable-energy positron beam POSH. This allows a new method of monitoring thin layers containing nanovoids or defects by depth-selective high-resolution positron beam analysis. The 2D-ACAR spectra of Si with a buried layer of nanocavities reveal the presence of two additional components, the first related to para-positronium (p-Ps) formation in the nanovoids, and a second one most likely related to unsaturated Si-bonds at the internal surface of the voids. The positronium is present in excited kinetic states with an average energy of 0.3 eV. Refilling of the cavities by means of low dose 3He implantation (1×1014 cm−2) followed by annealing reduces the formation of Ps and the width of the Ps peak in the ACAR spectrum. This width reduction is due to collisions of Ps with He atoms in the voids. In MgO, p-Ps formed with an initial energy of ~3 eV shows a final average energy of 1.6 eV at annihilation due to collisions with the cavity walls. Possibilities of this new, non-destructive method of monitoring the sizes of cavities and the evolution of nanovoid layers will be discussed.

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