Thermodynamics and Kinetics of Crystallization of Amorphous Si and Ge Produced by Ion Implantation

1983 ◽  
Vol 27 ◽  
Author(s):  
E.P. Donovan ◽  
F. Spaepen ◽  
D. Turnbull ◽  
J.M. Poate ◽  
D.C. Jacobson
Keyword(s):  
Noble Gas ◽  
Amorphous State ◽  
Heat Evolution ◽  
Precise Determination ◽  
Total Enthalpy ◽  
Kinetics Of Crystallization ◽  
Amorphous Si ◽  
Kinetics Of ◽  
Good Agreement

ABSTRACTAmorphous Si and Ge layers, produced by noble gas (Ar or Xe) implantation of single crystal substrates, have been crystallized in a differential scanning calorimeter (DSC). This technique allows determination of the growth velocity (which is proportional to the rate of heat evolution, ΔHac), and the total enthalpy of crystallization ΔHacAmorphous Ge was found to relax continuously to an amorphous state of lower free energy, with a total enthalpy of relaxation of 6.0 kJ.mole−1 before crystallization started. The regrowth velocity on (100) substrates,measured to be 4.2×1017 exp (−2.17eV/kT)Å/sec, is compared to other determinations. The value of ΔHac was found to be 11.66± 0.7 kJ.mole, in good agreement with ΔHac for amorphous Ge produced by other methods. For Si, ΔHac was determined to be 11.95± 0.7 kJ.mole without any evidence of heat release due to relaxation. The kinetics of crystallization measured by DSC are compared with those determined by other techniques. The effects of the implant profile on the regrowth velocity could also be observed directly in the DSC signal. The more accurate value of ΔHac allowed a more precise determination of the melting temperature of amorphous Si: Taℓ= 1420K.

scholarly journals Single-sided NMR for the measurement of the degree of cross-linking and curing

2018 ◽  
Vol 7 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Norbert Halmen ◽  
Christoph Kugler ◽  
Eduard Kraus ◽  
Benjamin Baudrit ◽  
Thomas Hochrein ◽  
...  
Keyword(s):  
Relaxation Times ◽  
Curing Kinetics ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
First Results ◽  
Non Destructive ◽  
Kinetics Of ◽  
Good Agreement

Abstract. The degree of cross-linking and curing is one of the most important values concerning the quality of cross-linked polyethylene (PE-X) and the functionality of adhesives and resin-based components. Up to now, the measurement of this property has mostly been time-consuming and usually destructive. Within the shown work the feasibility of single-sided nuclear magnetic resonance (NMR) for the non-destructive determination of the degree of cross-linking and curing as process monitoring was investigated. First results indicate the possibility of distinguishing between PE-X samples with different degrees of cross-linking. The homogeneity of the samples and the curing kinetics of adhesives can also be monitored. The measurements show good agreement with reference tests (wet chemical analysis, differential scanning calorimetry, dielectric analysis). Furthermore, the influence of sample temperature on the characteristic relaxation times can be observed.

Effect of C and Ge Concentration On The Thermal Stability of RTCVD Grown Si1-x-yGexCy Alloys

1997 ◽  
Vol 470 ◽  
Author(s):  
Patricia Warren ◽  
Stephane Retzmanick ◽  
Martin Gotza ◽  
Marc Begems
Keyword(s):  
Lattice Constant ◽  
Strain Relaxation ◽  
Mechanical Strain ◽  
Chemical Vapor ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
Cubic Silicon Carbide ◽  
Kinetics Of ◽  
Good Agreement

ABSTRACTSi / Si1-x-yGexCy / Si heterostructures containing up to 17 at.% Ge and 1.9 at.% C were grown on (001) silicon by low pressure Rapid Thermal Chemical Vapor Deposition, using a mixture of silane, germane and methylsilane, diluted in hydrogen. The samples were then annealed in a Rapid Thermal Processing furnace, under an atmospheric pressure of nitrogen, at temperatures ranging from 900 to 1130 °C.The samples were characterized using infrared spectroscopy and x-ray diffraction. SIMS profiling and TEM observation were performed on some of the samples.Substitutional C gradually disappeared, either precipitating out to form cubic silicon carbide (β-SiC), or simply vanishing into interstitial positions. In any case, the in-plane lattice constant remained constant after annealing, indicating that there was no mechanical strain relaxation by formation of misfit dislocations. The perpendicular lattice constant increased due to the decrease in substitutional C concentration, as well as it decreased due to the germanium out-diffusion. This variation of the strain during annealing was modeled, and allowed the determination of the kinetics of the substitutional carbon disappearance. The same behavior was observed for all samples. Indeed, the Cs disappearance rate was always increased for samples with higher initial Ge and C concentrations. The kinetics of this precipitation was found in very good agreement with previous published results.

Kinetics of Phosphorus Segregation in the Grain Boundaries of VVER-1000 Pressure Vessel Steels

2017 ◽  
Vol 375 ◽  
pp. 125-133 ◽  
Author(s):  
Boris Bokstein ◽  
Anatole N. Khodan ◽  
Mikhail V. Sorokin ◽  
Alexey O. Rodin ◽  
Evgeny A. Syutkin ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Auger Analysis ◽  
Phosphorus Segregation ◽  
Quantitative Measurements ◽  
Brittle Fractures ◽  
Fast Transport ◽  
Grain Bulk ◽  
Kinetics Of ◽  
Good Agreement

Methods of AES quantitative analysis were developed and applied for the determination of element concentrations at the surfaces of brittle fractures along grain boundaries. An attempt was made to take into account the presence of carbide precipitates and cleavage areas in the zone of the Auger analysis of their impact on the results of quantitative measurements. Obtained data were used for evaluation of the phosphorous segregation kinetics. The obtained results are consistent with thermodynamic modeling with CALPHAD method.Kinetics of segregation is analyzed with three models: (1) Langmuir - McLean theory; (2) model akin to kinetics of first order chemical reactions in solids; and (3) the model, which takes into account contribution of fast transport within subgrain networks and slow diffusion through the grain bulk. The two later models are in a good agreement with the experimental results.

scholarly journals Confronting expansion distances of planetary nebulae with Gaia DR2 measurements

2019 ◽  
Vol 625 ◽  
pp. A137 ◽  
Author(s):  
D. Schönberner ◽  
M. Steffen
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Precise Determination ◽  
Asymptotic Giant Branch ◽  
Correction Factors ◽  
Trigonometric Parallaxes ◽  
Formation And Evolution ◽  
Hydrodynamical Simulations ◽  
Good Agreement

Context. Individual distances to planetary nebulae are of the utmost relevance for our understanding of post-asymptotic giant-branch evolution because they allow a precise determination of stellar and nebular properties. Also, objects with individual distances serve as calibrators for the so-called statistical distances based on secondary nebular properties. Aims. With independently known distances, it is possible to check empirically our understanding of the formation and evolution of planetary nebulae as suggested by existing hydrodynamical simulations. Methods. We compared the expansion parallaxes that have recently been determined for a number of planetary nebulae with the trigonometric parallaxes provided by the Gaia Data Release 2. Results. Except for two out of 11 nebulae, we found good agreement between the expansion and the Gaia trigonometric parallaxes without any systematic trend with distance. Therefore, the Gaia measurements also prove that the correction factors necessary to convert proper motions of shocks into Doppler velocities cannot be ignored. Rather, the size of these correction factors and their evolution with time as predicted by 1D hydrodynamical models of planetary nebulae is basically validated. These correction factors are generally greater than unity and are different for the outer shell and the inner bright rim of a planetary nebula. The Gaia measurements also confirm earlier findings that spectroscopic methods often lead to an overestimation of the distance. They also show that even modelling of the entire system of star and nebula by means of sophisticated photoionisation modelling may not always provide reliable results. Conclusions. The Gaia measurements confirm the basic correctness of the present radiation-hydrodynamics models, which predict that both the shell and the rim of a planetary nebula are two independently expanding entities, created and driven by different physical processes, namely thermal pressure (shell) or wind interaction (rim), both of which vary differently with time.

PRECISE DETERMINATION OF BACKBONE STRUCTURE AND CONDUCTIVITY OF 3D PERCOLATION NETWORKS BY THE DIRECT ELECTRIFYING ALGORITHM

2009 ◽  
Vol 20 (03) ◽  
pp. 423-433 ◽  
Author(s):  
CHUNYU LI ◽  
TSU-WEI CHOU
Keyword(s):  
Efficient Algorithm ◽  
Precise Determination ◽  
Scaling Exponents ◽  
Resistor Network ◽  
Backbone Structure ◽  
Definition Of ◽  
First Time ◽  
Good Agreement

This paper confirms the applicability of a newly developed efficient algorithm, the direct electrifying method, for identifying backbone for 3D site and bond percolating networks. This algorithm is based on the current-carrying definition of backbone and carried out on the predetermined spanning cluster, which is assumed to be a resistor network. The scaling exponents so obtained for backbone mass, red bonds, and conductivity are in very good agreement with some existing results. The perfectly balanced bonds in 3D backbone structures are predicted first time to be 0.00179 ± 0.00009 and 0.00604 ± 0.00008 of the backbone mass for bond and site percolations, respectively.

scholarly journals Thermodynamic and kinetic features of the formation of amorphous state in films during quenching from the vapor state

2021 ◽  
Vol 29 (1) ◽  
pp. 57-60
Author(s):  
V. F. Bashev ◽  
S. I. Ryabtsev ◽  
F. F. Dotsenko
Keyword(s):  
Amorphous State ◽  
Effective Rate ◽  
Vapor State ◽  
Amorphous Phases ◽  
Plasma Sputtering ◽  
Ion Plasma ◽  
Nanocrystalline And Amorphous ◽  
Good Agreement ◽  
Kinetic Features

The method of modernized ion-plasma sputtering produced metastable states, including nanocrystalline and amorphous phases in films, even in alloys whose components do not mixed in the liquid state. The effective rate of energy relaxation at different modes of precipitation is theoretically estimated to be 1012 -1014 K/s during ion-plasma sputtering of atoms. On thermodynamic and kinetic states, different active and passive parameters for amorphization during sputtering are analyzed. The receiving expressions are in good agreement with the experimental results and contribute to the determination of further steps to obtain an amorphous state.

scholarly journals Precise determination of HPGe detector efficiency for gamma spectrometry measurements of environmental samples with variable geometry and density

Nukleonika ◽  
2017 ◽  
Vol 62 (1) ◽  
pp. 47-59 ◽  
Author(s):  
Manuel Barrera ◽  
Melquiades Casas-Ruiz ◽  
José J. Alonso ◽  
Juan Vidal
Keyword(s):  
Gamma Spectrometry ◽  
Environmental Samples ◽  
Hpge Detector ◽  
Attenuation Factor ◽  
Cylindrical Sample ◽  
Precise Determination ◽  
Energy Peak ◽  
Full Energy Peak Efficiency ◽  
Good Agreement

Abstract A methodology to determine the full energy peak efficiency (FEPE) for precise gamma spectrometry measurements of environmental samples with high-purity germanium (HPGe) detector, valid when this efficiency depends on the energy of the radiation E, the height of the cylindrical sample H, and its density ρ, is introduced. The methodology consists of an initial calibration as a function of E and H and the application of a self-attenuation factor, depending on the density of the sample ρ, in order to correct for the different attenuation of the generic sample in relation to the measured standard. The obtained efficiency can be used in the whole range of interest studied, E = 120–2000 keV, H = 1–5 cm, and ρ = 0.8–1.7 g/cm3, being its uncertainty below 5%. The efficiency has been checked by the measurement of standards, resulting in a good agreement between experimental and expected activities. The described methodology can be extended to similar situations when samples show geometric and compaction differences.

scholarly journals Open-boundary conditions in the deconfined phase

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
Adrien Florio ◽  
Olaf Kaczmarek ◽  
Lukas Mazur
Keyword(s):  
Boundary Conditions ◽  
Precise Determination ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
First Case ◽  
Two Temperatures ◽  
Channel Analysis ◽  
Pseudo Scalar ◽  
Good Agreement

AbstractIn this work, we consider open-boundary conditions at high temperatures, as they can potentially be of help to measure the topological susceptibility. In particular, we measure the extent of the boundary effects at $$T=1.5T_c$$T=1.5Tc and $$T=2.7T_c$$T=2.7Tc. In the first case, it is larger than at $$T=0$$T=0 while we find it to be smaller in the second case. The length of this “boundary zone” is controlled by the screening masses. We use this fact to measure the scalar and pseudo-scalar screening masses at these two temperatures. We observe a mass gap at $$T=1.5T_c$$T=1.5Tc but not at $$T=2.7T_c$$T=2.7Tc. Finally, we use our pseudo-scalar channel analysis to estimate the topological susceptibility. The results at $$T=1.5T_c$$T=1.5Tc are in good agreement with the literature. At $$T=2.7T_c$$T=2.7Tc, they appear to suffer from topological freezing, which prevents us from providing a precise determination of the topological susceptibility.

scholarly journals Spectrofluorometric Determination of Olanzapine and Fluphenazine Hydrochloride in Pharmaceutical Preparations and Human Plasma Using Eosin: Application to Stability Studies

2008 ◽  
Vol 91 (6) ◽  
pp. 1309-1317 ◽  
Author(s):  
Fathalla Belal ◽  
Amina El-Brashy ◽  
Nahed El-Enany ◽  
Nihal El-Bahay
Keyword(s):  
Human Plasma ◽  
Reaction Pathway ◽  
Pharmaceutical Preparations ◽  
Stability Studies ◽  
Quenching Effect ◽  
Spectrofluorometric Determination ◽  
The Mean ◽  
Kinetics Of ◽  
Good Agreement

Abstract A simple, rapid, and sensitive spectrofluorometric method has been developed for the determination of olanzapine (OLZ) and fluphenazine hydrochloride (FPZ HCl). The proposed method is based on the quantitative quenching effect of the studied drugs on the native fluorescence of eosin at pH 3.4 and 3.2 for OLZ and FPZ HCl, respectively. The fluorescence was measured at 547 nm after excitation at 323 nm. The fluorescence-concentration plots were rectilinear over the range of 0.051.0 and 0.101.0 g/mL, with lower detection limits of 1.8 103 and 1.2 103 g/mL, for OLZ and FPZ HCl, respectively. The proposed method was successfully applied to the analysis of commercial tablets and ampules containing the drugs, and the results were in good agreement with those obtained with reference methods. The proposed method was further applied to the determination of OLZ in spiked human plasma. The mean recovery was 98.62 0.24 (n 4). The method was also used for stability studies of FPZ HCl upon oxidation with hydrogen peroxide, and the kinetics of the reaction were studied. A proposal for the reaction pathway was postulated.

scholarly journals Continuous assay for acid phosphatase using 1-naphthyl phosphate as a substrate.

1997 ◽  
Vol 44 (4) ◽  
pp. 853-860 ◽  
Author(s):  
E Luchter-Wasylewska
Keyword(s):  
Aqueous Solution ◽  
Steady State ◽  
Acid Phosphatase ◽  
Reverse Micelles ◽  
Prostatic Acid Phosphatase ◽  
Precise Determination ◽  
Ph Range ◽  
Phosphatase Assay ◽  
Kinetics Of

The described continuous acid phosphatase assay is based on kinetics of the release of 1-naphthol in the course of the enzyme-catalyzed hydrolysis of 1-naphthyl phosphate, measured at 320 nm in aqueous solution and at 322 nm in sodium-bis(2-ethylhexyl)sulfosuccinate isooctane-water reverse micelles in a broad pH range (1.0-8.2). The method allows precise determination of the initial rate of the reaction and therefore may be used in the steady-state and pre-steady-state studies on the phosphatase-catalyzed reaction. The kinetic parameters (Km and kcat) for human prostatic acid phosphatase in aqueous solution and in reverse micelles, at pH 3.8, 4.5 and 5.7, by the proposed 1-naphthyl phosphate assay have been determined.

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