The interaction of conduction electrons with dislocations and grain boundaries in metals

1982 ◽  
Vol 60 (5) ◽  
pp. 766-778 ◽  
Author(s):  
R. A. Brown
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Dislocation Core ◽  
Electron Interaction ◽  
Resonance Model ◽  
Core Electron ◽  
The Core ◽  
Order Of Magnitude ◽  
Good Agreement ◽  
Grain Boundary Resistivity

Progress in understanding the contributions of dislocations and grain boundaries to the residual electrical resistivity in metals is reviewed. Following a summary of experimental data on dislocation and grain-boundary resistivity, it is shown that the resistivity due to the latter can be simply understood in terms of the independent scattering of electrons by individual dislocations of the ordered arrays which form the boundaries. The significance of this observation in establishing the relative dominance of dislocation core scattering over strain-field scattering, so far as charge transport is concerned, is discussed. A brief review of the multitude of dislocation–electron scattering calculations which have appeared in the literature is presented. This shows that theories which neglect the core contribution have invariably failed to account for the order of magnitude of the observed resistivity, again suggesting that core scattering dominates the issue. A simple formula derived from a resonance model of the core-electron interaction is shown to yield dislocation (and hence grain-boundary resistivity) contributions in good agreement with experiment.

A Highly Reliable Al Line with Controlled Texture and Grain Boundaries

1995 ◽  
Vol 391 ◽  
Author(s):  
M. Hasunuma ◽  
H. Toyoda ◽  
T. Kawanoue ◽  
S. Ito ◽  
H. Kaneko ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Empirical Relation ◽  
Boundary Structure ◽  
Homogeneous Microstructure ◽  
Grain Boundary Structure ◽  
Dislocation Arrays ◽  
Order Of Magnitude ◽  
Individual Grains

AbstractIn order to clarify the relationship between Al line reliability and film microstructure, especially grain boundary structure and crystal texture, we have tested three kinds of highly textured Al lines, namely, single-crystal Al line, quasi-single-crystal Al line and hypertextured Al line, and two kinds of conventional Al lines deposited on TiN/Ti and on SiO2. Consequently, the empirical relation between the electromigration (EM) lifetime of Al line † and the (111) full width at half maximum (FWHM) value ω is described by † ∝ ω-2 [1]. This improvement of Al line reliability results from as following reasons; firstly, homogeneous microstructure and high activation energy of 1.28eV for the single-crystal Al line (ω=0.18°); secondly, sub-grain boundaries which consisted of dislocation arrays found in the quasi-single-crystal Al line (ω=0.26°) has turned out to be no more effective mass transport paths because dislocation lines are perpendicular to the direction of electron wind. Although there exist plural grain boundary diffusion paths in the newly developed hypertextured Al line (ω=0.5°) formed by using an amorphous Ta-Al underlayer {1], the vacancy flux along the line has been suppressed to the same order of magnitude of single crystal line. It has been clarified that the decrease of FWHM value has promoted the formation of sub-grain boundaries and low-angle boundaries with detailed orientation analysis of individual grains in the hypertextured film. The longer EM lifetime for the hypertextured Al line is considered to be due to the small grain boundary diffusivities for these stable grain boundaries, and this diffusivity reduction resulted in the suppression of void/hillock pair in the Al lines. These results have confirmed that controlling texture and/or grain boundary itself is a promising approach to develop reliable Al lines which withstand higher current densities required in future ULSIs.

Quantum-Chemical Simulation of Silicon Grain Boundaries Contaminated by Oxygen and Carbon

2005 ◽  
Vol 108-109 ◽  
pp. 235-240
Author(s):  
Anis M. Saad ◽  
Alex L. Pushkarchuk ◽  
A.V. Mazanik ◽  
A.K. Fedotov ◽  
S.A. Kuten
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Conduction Band ◽  
Atomic Structure ◽  
Quantum Chemical ◽  
Electronic States ◽  
Quantum Chemical Simulation ◽  
The Core ◽  
Chemical Simulation

Transformation of the “core” atomic structure and electronic states of the tilt Σ5 θ = 37° [001]/(130) grain boundary in poly-Si due to incorporation of carbon atoms into the oxygencontaining complexes is studied using MM and MO LCAO methods. Different numbers n = 1 ÷ 4 of C-atoms were introduced into the 5-fold interstitial positions in the initial O-containing complexes built-up from SiO3 and SiO4 configurations at the GB “core”. Incorporation of C-atoms into SiO3 and SiO4 complexes leads to the formation of Si-O-C-Si chains and shifting of the donorlike levels generated by SiO3 and SiO4 configurations to the bottom of the conduction band with an increase in the number of the incorporated C-atoms.

The Influence of Grain Boundary Migration on the Diffusion Behaviour of Thin Films

1980 ◽  
Vol 35 (6) ◽  
pp. 613-618
Author(s):  
E. Ehrmann-Falkenau ◽  
A. Wagendristel
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Boundary Surface ◽  
Depth Profiling ◽  
Lattice Diffusion ◽  
Grain Boundary Migration ◽  
Order Of Magnitude ◽  
Diffusion Behaviour

Simultaneous grain boundary-, surface- and lattice diffusion in hypothetical thin film couples of miscible components was computer simulated. On this basis the diffusion into fixed and moving grain boundaries is discussed with respect to the determination of diffusivities by depth profiling methods. The data evaluated from the synthesised depth profiles according to Whipple-Le Claire as well as to Gilmer and Farrell were compared with the diffusivities used for the computation. Agreement was found for systems with a fixed grain boundary network. Moving grain boundaries, however, may cause errors of an order of magnitude towards lower grain boundary diffusivities

scholarly journals Z-Contrast STEM Imaging and Ab-Initio Calculations of Grain Boundaries in SrTiO3

1999 ◽  
Vol 586 ◽  
Author(s):  
Miyoung Kim ◽  
Nigel D. Browning ◽  
Stephen J. Pennycook ◽  
Karl Sohlberg ◽  
Sokrates T. Pantelides
Keyword(s):  
Grain Boundary ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Grain Boundaries ◽  
Theoretical Calculations ◽  
Intrinsic Property ◽  
Dislocation Core ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Z Contrast

ABSTRACTThe understanding of electrical properties of grain boundaries in perovskites is essential for their application to capacitors, varistors and positive-temperature coefficient resistors. The origin of the electrical activity is generally attributed to the existence of charged defects in grain boundaries, usually assumed to be impurities, which set up a double Schottky barrier as they are screened by dopants in the adjacent bulk crystal. Microscopic understanding of the origin of the grain boundary charge, however, has not been achieved. It is not known yet if the charged grain boundary states are an intrinsic property of a stoichiometric grain boundary, arise from nonstoichiometry, or are caused by impurities. Here, the relation between atomic structure and electronic properties is studied by combining experiment with ab-initio calculations. The starting structures for theoretical calculations were obtained from Z-contrast images combined with electron energy loss spectroscopy to resolve the dislocation core structures comprising the boundary. Dislocation core reconstructions are typical of all grain boundaries so far observed in this material. They avoid like-ion repulsion, and provide alternative sites for cation occupation in the grain boundaries. Optimized atomic positions are found by total energy calculations. Calculated differences in vacancy formation energies between the grain boundaries and the bulk suggest that vacancy segregation can account for the postulated grain boundary charge.

(110) facets and dislocation structure of low-angle grain boundaries in YBa2Cu3O7−δ and Y0.7Ca0.3Ba2Cu3O7−δ thin film bicrystals

2007 ◽  
Vol 22 (4) ◽  
pp. 950-957 ◽  
Author(s):  
Xueyan Song
Keyword(s):  
Thin Film ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Current Flow ◽  
Dislocation Core ◽  
Current Transport ◽  
Contrast Imaging ◽  
Grain Boundary Plane ◽  
Z Contrast

The facet and dislocation structure of 5° and 7° [001]-tilt grain boundaries of YBa2Cu3O7−δ (YBCO) and Y0.7Ca0.3Ba2Cu3O7−δ (YCaBCO) thin film bicrystals were studied. A 24° [001]-tilt YBCO grain boundary was also examined to contrast with the low angle grain boundary faceting behavior. All the low-angle grain boundaries exhibit strong faceting along (100)/(010) and (110) and possess both straight symmetric segments containing equally spaced [100] unit dislocations and step asymmetric segments composed of (110) and (100)/(010) facets. Grain boundaries with a higher degree of meander acquired up to 40% (110) facets. The atomic structure of (110) facets was revealed by the atomic resolution Z-contrast imaging. The (110) facets are dissociated for both the YBCO and YCaBCO grain boundaries. We also found the Ca-doped (110) facets to be more extended along the grain boundary plane, consistent with our earlier finding of a dissociated dislocation core in Ca-doped (100) facets. These 5° and 7° misorientations that we studied are just in the range at which YBCO grain boundaries start to become obstacles to current flow. The above results will be helpful for understanding the current transport across YBCO low-angle grain boundaries.

Transient creep in fine-grained polycrystalline Al2O3 with Lu3+ ion segregation at the grain boundaries

2001 ◽  
Vol 16 (3) ◽  
pp. 716-720 ◽  
Author(s):  
Hidehiro Yoshida ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Testing Temperature ◽  
Grain Boundary Sliding ◽  
Transient Creep ◽  
Transient Time ◽  
Fine Grained ◽  
Boundary Sliding ◽  
The Difference ◽  
Good Agreement

The creep deformation in fine-grained polycrystalline Al2O3 is highly suppressed by the addition of 0.1 mol% LuO1.5. The transient creep behavior in Lu-doped Al2O3 was examined at the testing temperature of 1250–1350 °C, and the data were analyzed in terms of the effect of stress and temperature on the extent of transient time and strain. The experimental data on the transient creep in Lu-doped Al2O3 showed good agreement with the prediction from a time function of the transient and the steady-state creep associated with grain boundary sliding as well as an undoped one. The difference in the transient creep between Lu-doped and undoped Al2O3 can also be explained by the retardation of grain boundary diffusion due to the Lu3+ ions segregation in the grain boundaries.

Core-polarization-corrected multiconfiguration Dirac–Fock oscillator strengths and excitation energies for the 5s2 1S0 – 5s5p 3P1, 1P1 transitions in Sr I and Y II spectra

1987 ◽  
Vol 65 (12) ◽  
pp. 1612-1619 ◽  
Author(s):  
J. Migdalek ◽  
W. E. Baylis
Keyword(s):  
Electron Correlation ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Core Electron ◽  
Polarization Model ◽  
Core Polarization ◽  
The Core ◽  
Relativistic Configuration ◽  
Comparison Of The Results ◽  
Good Agreement

Energies and oscillator strengths for the spin-allowed 5s2 1S0 – 5s5p 1P1 and spin-forbidden 5s2 1S0 – 5s5p 3P1 transitions in neutral strontium and singly ionized yttrium are determined in relativistic multiconfiguration Dirac–Fock computations where modest relativistic configuration mixing to represent intravalence correlation is combined with a polarization model to account for valence–core electron correlation. It is demonstrated, by comparison of the results corrected for electron correlation with those obtained from relativistic intermediate coupling Dirac–Fock calculations, that both intravalence and core–valence correlation are important for achieving good agreement with experiment. However, for neutral strontium it is the intravalence correlation that seems to be more important whereas for the isoelectronic singly ionized yttrium the core-valence correlation, as represented by the core-polarization model, dominates. A delicate balance resulting from the partial collapse of the 4d orbital in Y+ may be a reason for the greater sensitivity to core polarization in this system.

Vertex Dynamics Simulations of Orientation Dependent Recovery in Deformed Aluminium Single Crystals

2011 ◽  
Vol 702-703 ◽  
pp. 639-642
Author(s):  
Adhish Majumdar ◽  
Claire Maurice ◽  
Julian H. Driver
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Dynamics Simulation ◽  
Boundary Misorientation ◽  
Annealing Behaviour ◽  
The Common ◽  
Dynamics Simulations ◽  
Orientation Dependency ◽  
Good Agreement

A 2-dimensional vertex dynamics simulation is applied to the annealing behaviour of deformed Aluminium single crystals having different orientations. It is observed in experiments that deformed single crystals of different orientations - typically the common rolling textures like Goss (110)[001], Brass (110)[1-12], Cube (001)[100] – exhibit remarkably different rates of recovery. It is suggested that this difference arises from the deformation microstructures, with sub-grain boundaries of various misorientation values. The sub-grain boundary mobilities and energies, being strong functions of the boundary misorientation, thus affect the recovery rates. This effect is illustrated using vertex dynamics simulation on the same orientations and schematic deformation substructures as above. Good agreement is obtained for the orientation dependency of recovery.

Elastic Properties of Grain Boundaries in Copper

1989 ◽  
Vol 153 ◽  
Author(s):  
James B. Adams ◽  
Wilhelm G. Wolfer ◽  
Stephen M. Foiles
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Elastic Properties ◽  
Elastic Constants ◽  
Elastic Behavior ◽  
Order Of Magnitude

AbstractThe elastic constants of a Σ5 (100) twist grain boundary are calculated on a monolayer-by-monolayer basis, and the elastic behavior is shown to differ by up to an order of magnitude from bulk-like behavior. This unusual elastic behavior is found to be similar to that of uniaxiallystrained crystals, since the grain boundaries themselves are regions which are strained (expanded) in one direction.

scholarly journals Модель растворения пор на границах зерен при отжиге ультрамелкозернистого алюминиевого сплава

2021 ◽  
Vol 47 (18) ◽  
pp. 40
Author(s):  
М.Ю. Гуткин ◽  
Т.С. Орлова ◽  
Н.В. Скиба
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Total Energy ◽  
Grain Boundaries ◽  
Ultrafine Grained ◽  
Model Pore ◽  
Ultrafine Grained Materials ◽  
Good Agreement ◽  
Zr Alloy

A theoretical model which describes the mechanism of pore dissolution at grain boundaries in ultrafine-grained materials during the ageing annealing is suggested. Within the framework of the model, pore dissolution occurs due to the emission of vacancies and the climb of grain-boundary dislocations along the grain boundary towards the pore. It is shown that in this case there is a significant decrease in the total energy of the system. The results of the model are in good agreement with the available experimental observations of pore dissolution during annealing of ultrafine-grained Al-Zr alloy.

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