Nitrogen Self-Diffusion in Polycrystalline Si3N4 Films: Isotope Heterostructures vs. Gas-Exchange

2005 ◽  
Vol 237-240 ◽  
pp. 512-517 ◽  
Author(s):  
Harald Schmidt ◽  
Günter Borchardt ◽  
Mario Rudolphi ◽  
H. Baumann ◽  
Michael Bruns ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Exchange ◽  
Activation Enthalpy ◽  
Diffusion Mechanism ◽  
Exchange Process ◽  
Exchange Method ◽  
Surface Exchange ◽  
Exponential Factor ◽  
Temperature Range ◽  
Self Diffusion

The self-diffusion of nitrogen is investigated in polycrystalline thin silicon nitride films using a gas-exchange method (14N2/Si3 15N4) in comparison to Si3 14N4/Si3 15N4/Si3 14N4 isotope heterostructures. The films are produced by reactive r. f. magnetron sputtering. Depth profile analysis is carried out with secondary ion mass spectrometry (SIMS), secondary neutral mass spectrometry (SNMS), and nuclear resonant reaction analysis (NRRA). The nitrogen diffusivities determined with the use of isotope heterostructures follow an Arrhenius law in the temperature range between 1200 and 1700 °C with an activation enthalpy of DH = 4.9 eV and a pre-exponential factor of D0 = 1 x 10-6 m2/s, indicating a conventional diffusion mechanism via localized point defects. Using the gas-exchange method, the nitrogen diffusivities could be obtained only in the temperature range between 1600 and 1700 °C. This is due to the fact that at temperatures below 1600 °C the surface exchange process with its high activation enthalpy (about 10 eV) is rate limiting, leading to non detectable diffusion profiles. The application of the different methods of depth profiling leads to the same diffusivities within estimated errors.

Diffusion of ion-implanted Boron and Silicon in Germanium

2004 ◽  
Vol 809 ◽  
Author(s):  
Suresh Uppal ◽  
A. F. W. Willoughby ◽  
J. M. Bonar ◽  
N. E. B. cowern ◽  
R. J. H. Morris ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Resolution ◽  
Diffusion Coefficients ◽  
Doping Concentration ◽  
Diffusion Mechanism ◽  
Concentration Profiles ◽  
Furnace Annealing ◽  
Temperature Range ◽  
Self Diffusion ◽  
Secondary Ion

ABSTRACTThe diffusion of B and Si in Ge is studied using implantation doping. Concentration profiles after furnace annealing in the temperature range 800–900 °C were obtained using high resolution secondary ion mass spectroscopy (SIMS). Diffusion coefficients are calculated by fitting the annealed profiles. For B, we obtain diRusivity values which are two orders of magnitude slower than previously reported in literature. An activation energy of 4.65(±0.3) eV is calculated for B diffusion in Ge. The results suggest that diffusion mechanism other than vacancy should be considered for B diffusion in Ge. For Si diffusion in Ge, the diffusivity values calculated in the temperature range 750–875 °C are in agreement with previous work. The activation energy of 3.2(±0.3) eV for Si diffusion is closer to that for Ge self-diffusion which suggests that Si diffusion in Ge occurs via the same mechanism as in Ge self-diffusion.

Diffusion of Nb in Nb-H Alloys

2005 ◽  
Vol 237-240 ◽  
pp. 346-351
Author(s):  
Yoshihiro Yamazaki ◽  
Takahiro Iida ◽  
Yoshiaki Iijima ◽  
Yuh Fukai
Keyword(s):  
Diffusion Coefficient ◽  
Activation Energies ◽  
The Self ◽  
Exponential Factor ◽  
Temperature Range ◽  
Self Diffusion ◽  
Diffusion Enhancement ◽  
The Difference ◽  
Self Diffusion Coefficient ◽  
Hydrogen Dissolution

Self-diffusion coefficient of 95Nb in NbHx alloys (x=0.05,0.25 and 0.3) has been determined in the temperature range from 823 to 1323 K by using a serial sputter-microsectioning technique. The self-diffusion coefficient of Nb in the NbHx alloys are larger than that in Nb, suggesting that vacancies are formed by hydrogen dissolution, that is, the formation of hydrogen-induced vacancies. The value of the pre-exponential factor for the Nb diffusion in the NbH0.05 alloy is five times larger than that in Nb, while the difference in the activation energies between the NbH0.05 alloy and pure Nb is small. The self-diffusion enhancement in the NbH0.05 alloy is mainly caused by lowering in vibrational frequencies of atoms in the immediate neighborhood of hydrogen-induced vacancies.

Atomic Motion and Diffusion Mechanism of Hydrogen in Amorphous Ceramics of the System Si-B-C-N

2007 ◽  
Vol 263 ◽  
pp. 63-68
Author(s):  
Wolfgang Gruber ◽  
Günter Borchardt ◽  
Harald Schmidt
Keyword(s):  
Chemical Potential ◽  
Secondary Ion Mass Spectrometry ◽  
Activation Enthalpy ◽  
Diffusion Mechanism ◽  
Depth Profiling ◽  
Exponential Factor ◽  
Transport Path ◽  
Entropy Factor ◽  
Amorphous Sic ◽  
And Diffusion

In this work we investigated the mobility of hydrogen in amorphous ceramics with the composition Si13B13C60N13 (AM26C). The material was derived from a pre-ceramic polymer and thermolyzed at 1000 °C. After thermolysis the AM26C ceramics are assumed to be separated in an amorphous SiC phase and an amorphous C(BN)x phase. To measure the diffusivities we used deuterium as a tracer, which was introduced via isotope exchange from the gas phase at temperatures between 700 °C and 1100 °C. Depth profiling was done with secondary ion mass spectrometry (SIMS). The profiles could be fitted with complementary error functions. The diffusivities obey an Arrhenius law. The activation enthalpy is 0.8 eV, the pre-exponential factor is 5×10-12 m2 s-1. These values are close to those found for glassy carbon and thin amorphous C-B-N films as reported in the literature. We therefore conclude that the amorphous C(BN)x phase is the transport path for hydrogen in AM26C ceramics. A direct interstitial diffusion mechanism can account for the activation enthalpy of 0.8 eV. The low value for the pre-exponential factor is attributed to an entropy factor arising from the temperature dependence of the chemical potential of hydrogen.

Self-Diffusion in Isotopically Controlled Heterostructures of Elemental and Compound Semiconductors

1998 ◽  
Vol 527 ◽  
Author(s):  
H. Bracht ◽  
E. E. Haller ◽  
K. Eberl ◽  
M. Cardona ◽  
R. Clark-Phelps
Keyword(s):  
Temperature Dependence ◽  
Diffusion Coefficients ◽  
Secondary Ion Mass Spectrometry ◽  
Activation Enthalpy ◽  
Exponential Factor ◽  
Self Diffusion ◽  
Diffusion Studies ◽  
Exponential Factors ◽  
Secondary Ion ◽  
Diffusion Profiles

ABSTRACTWe report self-diffusion studies of silicon between 855 and 1388°C in highly enriched epitaxial 28Si layers. Diffusion profiles of 30Si and 29Si are determined with high resolution secondary ion mass spectrometry (SIMS). The temperature dependence of the Si self-diffusion coefficients is accurately described with an activation enthalpy of 4.76 eV and a pre-exponential factor of 560 cm2s-1. The single activation enthalpy indicates that Si self-interstitials dominate self-diffusion over the whole temperature range investigated. Self- and interdiffusion in buried Al71GaAs/Al69GaAs/71GaAs isotope heterostructures with different Al composition is measured between 800 and 1160°C. Ga self-diffusion in AlGaAs and interdiffusion of Al and Ga at the AlGaAs/GaAs interface show that Ga diffusion decreases with increasing Al composition and that the interdiffusion coefficient depends linearly on Al concentration. Furthermore Al is found to diffuse more rapidly into GaAs than Ga diffuses in GaAs. The temperature dependence of Ga and Al diffusion in GaAs and of Ga diffusion in AlGaAs is described by a single activation enthalpy in the range of 3.6±0.1 eV, but by different pre-exponential factors. Differences found for Ga and Al diffusion in GaAs and for Ga diffusion in AlGaAs with different Al concentrations are discussed.

Disordering and Characterization Studies of 69GaAs/71GaAs Isotope Superlattice Structures: The Effect of Outdiffusion of the Substrate Dopant Si

1992 ◽  
Vol 262 ◽  
Author(s):  
T. Y. Tan ◽  
H. M. You ◽  
S. Yu ◽  
U. M. Gitesele ◽  
W. Jäger ◽  
...  
Keyword(s):  
Thermal Equilibrium ◽  
Activation Enthalpy ◽  
N Value ◽  
Temperature Range ◽  
Self Diffusion ◽  
Gaas Substrates ◽  
Characterization Studies ◽  
Superlattice Structures ◽  
Cv Measurements ◽  
P Type

ABSTRACTUndoped 69GaAs/71GaAs isotope superlattice structures grown by MBE on n-type GaAs substrates, doped by Si to ∼3×1018 cm−3, have been used to study Ga self-diffusion in GaAs by disordering reactions. In the temperature range of 850–960°C, the SIMS measured Ga self-diffusivity values showed an activation enthalpy of 4 eV, and are larger than previously compiled Ga self-diffusivity and Al-Ga interdiffusivity values obtained under thermal equilibrium and intrinsic conditions, which are characterized by a 6 eV activation enthalpy. SIMS, CV, and TEM characterizations showed that the as-grown superlattice layers were intrinsic which became p-type with hole concentrations up to ∼2×1017 cm−3 after annealing, because the layers contain carbon. Dislocations of a density of ∼106-107 cm−2 were also present. However, the factor responsible for the presently observed larger Ga self-diffusivity values appears to be Si outdiffusion from the substrate, which was determined using CV measurements. Outdiffusion of Si decreases the n value in the substrate which causes the release of excess Ga vacancies into the superlattice layers where the supersaturated Ga vacancies enhance Ga self-diffusion.

Li Diffusion in (110) Oriented LiNbO3 Single Crystals

2013 ◽  
Vol 333 ◽  
pp. 33-38 ◽  
Author(s):  
Johanna Rahn ◽  
Lars Dörrer ◽  
Benjamin Ruprecht ◽  
Paul Heitjans ◽  
Harald Schmidt
Keyword(s):  
Mass Spectrometry ◽  
Single Crystals ◽  
Secondary Ion Mass Spectrometry ◽  
Activation Enthalpy ◽  
Ion Beam ◽  
Diffusion Mechanism ◽  
Three Dimensional ◽  
Arrhenius Law ◽  
Dimensional Diffusion ◽  
Secondary Ion

Li diffusion is investigated in Li2O-deficient, (110) oriented LiNbO3single crystals in the temperature range between 523 and 673 K by secondary ion mass spectrometry. A thin layer of ion-beam sputtered isotope enriched6LiNbO3was used as a tracer source, which allows one to study pure isotope interdiffusion. The diffusivities coincide with those of (001) oriented single crystals and follow the Arrhenius law with an activation enthalpy of 1.33 eV. The results prove the existence of a three-dimensional diffusion mechanism.

Direct determination of the self-diffusion mechanism in bccβ-titanium

1989 ◽  
Vol 39 (8) ◽  
pp. 5025-5034 ◽  
Author(s):  
G. Vogl ◽  
W. Petry ◽  
Th. Flottmann ◽  
A. Heiming
Keyword(s):  
Diffusion Mechanism ◽  
Direct Determination ◽  
The Self ◽  
Self Diffusion

Experimental research on scavenging process of opposed-piston two-stroke gasoline engine based on tracer gas method

2021 ◽  
pp. 146808742110366
Author(s):  
Fukang Ma ◽  
Wei Yang ◽  
Yifang Wang ◽  
Junfeng Xu ◽  
Yufeng Li
Keyword(s):  
Gas Exchange ◽  
Exchange Process ◽  
Delivery Ratio ◽  
Tracer Gas ◽  
Piston Motion ◽  
Trapped Air ◽  
Exchange Performance ◽  
Gdi Engine ◽  
Gas Exchange Process ◽  
Scavenging Efficiency

The scavenging process of two stroke engine includes free exhaust, scavenging, and post intake process, which clears the burned gas in cylinder and suctions the fresh air for next cycle. The gas exchange process of Opposed-Piston Two-Stroke (OP2S) engine with gasoline direct injection (GDI) engine is a uniflow scavenging method between intake port and exhaust port. In order to investigate the characteristics of the gas exchange process in OP2S-GDI engine, a specific tracer gas method (TGM) was developed and the experiments were carried out to analyze the gas exchange performance under different intake and exhaust conditions and opposed-piston movement rule. The results show that gas exchange performance and trapped gas mass are significantly influenced by intake pressure and exhaust pressure. And it has a positive effect on the scavenging efficiency and the trapped air mass. Scavenging efficiency and trapped air mass are almost independent of pressure drop when the delivery ratio exceeds 1.4. Consequently, the delivery ratio ranges from 0.5 to 1.4 is chosen to achieve an optimization of steady running and minimum pump loss. The opposed piston motion phase difference only affects the scavenging timing. Scavenging performance is mainly influenced by scavenging timing and scavenging duration. With the increased phase difference of piston motion, the scavenging efficiency and delivery ratio increased gradually, the trapping efficiency would increase first and decrease then and reaches its maximum at 14°CA.

Dynamic Study on Vacuum Pyrolysis Reaction of Chinese Fir Sawdust Biomass

2012 ◽  
Vol 512-515 ◽  
pp. 375-378
Author(s):  
Su Wen Yang ◽  
Jian Min Yi ◽  
Ke Qiang Qiu ◽  
Xin Deng ◽  
Jian Shan Chen
Keyword(s):  
Heating Rate ◽  
Free Water ◽  
Chinese Fir ◽  
Peak Temperature ◽  
Gravimetric Analysis ◽  
Water Desorption ◽  
Exponential Factor ◽  
Pyrolysis Reaction ◽  
Temperature Range ◽  
Vacuum Pyrolysis

This thesis does thermal gravimetric analysis（TGA）studies on Chinese fir sawdust biomass by integrated thermal analyzer under vacuum conditions. Through the analysis on lostmass curve at different heating rate of 10, 15, 20 and 30°C/min, we found the process of Chinese fir sawdust vacuum pyrolysis can be mainly divided into three stages: evaporation of free water and combined water desorption, rapid lostmass of pyrolysis and slow decomposition of residues. The lostmass major temperature range is between 250 ~ 450°C, the peak temperature is between 365 ~ 400°C. When the pyrolysis temperature is 500°C, vacuum pyrolysis reaction of Chinese fir sawdust has basically completed. As the heating rate rises, the lostmass curve is moving to the right, the peak temperature is shifting to higher temperature, and the temperature range of thermal decomposition reaction widens significantly. According to experimental datas, we tried to obtain the vacuum pyrolysis dynamic parameters of Chinese fir sawdust, and the results are that the apparent activation energy of vacuum pyrolysis reaction of Chinese fir sawdust biomass is 128.34kJ/mol, with the pre-exponential factor being 6.42×109 and reaction order being 1.08, similar to first order reaction.

Structural and Mechanical Properties of Nanophase Ni: A Molecular-Dynamics Study of the Influence of Grain-Boundary Structure on Elastic and Plastic Behavior

1997 ◽  
Vol 492 ◽  
Author(s):  
H. Van Swygenhoven ◽  
M. Spaczér ◽  
A. Caro
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Diffusion Mechanism ◽  
Distribution Functions ◽  
Boundary Structure ◽  
Plastic Behavior ◽  
Self Diffusion ◽  
Common Neighbour ◽  
Grain Boundary Structure

ABSTRACTMolecular dynamics computer simulations of high load plastic deformation at temperatures up to 500K of Ni nanophase samples with mean grain size of 5 nm are reported. Two types of samples are considered: a polycrystal nucleated from different seeds, each having random location and random orientation, representing a sample with mainly high angle grain boundaries, and polycrystals with seeds located at the same places as before, but with a limited missorientation representing samples with mainly low angle grain boundaries. The structure of the grain boundaries is studied by means of pair distribution functions, coordination number, atom energetics, and common neighbour analysis. Plastic behaviour is interpreted in terms of grain-boundary viscosity, controlled by a self diffusion mechanism at the disordered interface activated by thermal energy and stress.

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