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Journal articles on the topic 'Dislocation transport'

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Author: Grafiati

Published: 10 December 2022

Last updated: 29 January 2023

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1

Gbemou, Kodjovi, Jean Marc Raulot, Vincent Taupin, and Claude Fressengeas. "Continuous Modeling of Dislocation Cores Using a Mechanical Theory of Dislocation Fields." Materials Science Forum 879 (November 2016): 2456–62. http://dx.doi.org/10.4028/www.scientific.net/msf.879.2456.

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A one-dimensional model of an elasto-plastic theory of dislocation fields is developed to model planar dislocation core structures. This theory is based on the evolution of polar dislocation densities. The motion of dislocations is accounted for by a dislocation density transport equation where dislocation velocities derive from Peach-Koehler type driving forces. Initial narrow dislocation cores are shown to spread out by transport under their own internal stress field and no relaxed configuration is found. A restoring stress of the lattice is necessary to stop this infinite relaxation and it is derived from periodic sinusoidal energy of the crystal. When using the Peierls sinusoidal potential, a compact equilibrium core configuration corresponding to the Peierls analytical solution is obtained. The model is then extended to use generalized planar stacking fault energies as an input and is applied to the determination of properties of planar dislocation cores in crystalline materials. Dissociations of edge and screw dislocation cores in basal and prismatic planes of Zirconium are shown.

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2

Lund, Fernando, and Bruno Scheihing-Hitschfeld. "The Scattering of Phonons by Infinitely Long Quantum Dislocations Segments and the Generation of Thermal Transport Anisotropy in a Solid Threaded by Many Parallel Dislocations." Nanomaterials 10, no. 9 (August 29, 2020): 1711. http://dx.doi.org/10.3390/nano10091711.

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A canonical quantization procedure is applied to the interaction of elastic waves—phonons—with infinitely long dislocations that can oscillate about an equilibrium, straight line, configuration. The interaction is implemented through the well-known Peach–Koehler force. For small dislocation excursions away from the equilibrium position, the quantum theory can be solved to all orders in the coupling constant. We study in detail the quantum excitations of the dislocation line and its interactions with phonons. The consequences for the drag on a dislocation caused by the phonon wind are pointed out. We compute the cross-section for phonons incident on the dislocation lines for an arbitrary angle of incidence. The consequences for thermal transport are explored, and we compare our results, involving a dynamic dislocation, with those of Klemens and Carruthers, involving a static dislocation. In our case, the relaxation time is inversely proportional to frequency, rather than directly proportional to frequency. As a consequence, the thermal transport anisotropy generated on a material by the presence of a highly-oriented array of dislocations is considerably more sensitive to the frequency of each propagating mode, and, therefore, to the temperature of the material.

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3

Murphy, John D., A. Giannattasio, Charles R. Alpass, Semih Senkader, Robert J. Falster, and Peter R. Wilshaw. "The Influence of Nitrogen on Dislocation Locking in Float-Zone Silicon." Solid State Phenomena 108-109 (December 2005): 139–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.108-109.139.

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Dislocation locking by nitrogen impurities has been investigated in float-zone silicon with nitrogen concentrations of 2.2 x 1015cm-3 and 3 x 1014cm-3. The stress required to unlock dislocations pinned by nitrogen impurities was measured as a function of annealing time (0 to 2500 hours) and temperature (550 to 830°C). For all conditions investigated the locking effect was found to increase linearly with annealing time before saturating. It is assumed that the rate of increase of unlocking stress with annealing time is a measure of transport of nitrogen to the dislocation core. This rate of increase was found to depend linearly on nitrogen concentration, which is consistent with transport by a dimeric species, whose activation energy for diffusion is approximately 1.4eV. The saturation unlocking stress has been found to be dependent on the nitrogen concentration. Additionally, the temperature dependence of the stress required to move dislocations immobilised by nitrogen impurities has been studied. By assuming a value for the binding energy of the nitrogen to the dislocation, the density of the locking species at the dislocation core has been calculated.

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4

Maroudas, Dimitris, and Robert A. Brown. "Constitutive modeling of the effects of oxygen on the deformation behavior of silicon." Journal of Materials Research 6, no. 11 (November 1991): 2337–52. http://dx.doi.org/10.1557/jmr.1991.2337.

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A systematic theory is presented that models the effects of interstitial oxygen on the deformation behavior of silicon. The theory is based on calculation of the dependence of the dislocation velocity on the applied stress in the crystal and determination of the locking and unlocking stresses for dislocation motion. Internal stresses in the oxygen-hardened crystals are modeled by the superposition of the unlocking stress, a back stress due to the interaction between mobile dislocations, and an internal stress that arises from the interaction between a dislocation and the oxygen cloud around other dislocations. The initiation of dislocation multiplication is modeled as a two-step thermally activated process; the first step is the unlocking of the dislocation and the second step is the formation of jogs along the dislocation line. The coupled model for oxygen transport and dislocation motion is used to simulate crystal deformation in dynamic experiments and to reproduce stress-strain curves. The predictions of the initial stage of deformation are in good agreement with the experimental data of Yonenaga et al. [J. Applied Phys. 56, 2346 (1984)].

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5

NITTA, S., T. KASHIMA, R. NAKAMURA, M. IWAYA, H. AMANO, and I. AKASAKI. "MASS TRANSPORT OF GaN AND REDUCTION OF THREADING DISLOCATIONS." Surface Review and Letters 07, no. 05n06 (October 2000): 561–64. http://dx.doi.org/10.1142/s0218625x00000567.

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Mass transport of patterned GaN at around 1100°C in nitrogen with an ammonia atmosphere has been discovered for the first time. The mass transport process is found to be affected by the anisotropy of surface energy of GaN. Behaviors of threading dislocations which are predominantly of the mixed type and the pure edge type are affected by the anisotropy during mass transport. Mixed type dislocations are bent keeping the geometrical relationship normal to the surfaces, while pure edge type dislocations are bent horizontally. This new-found process, the so-called "mass transport epitaxy," is one of the best methods for achieving low dislocation density GaN on the highly lattice-mismatched substrate.

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6

Gagel, J., D. Weygand, and P. Gumbsch. "Discrete Dislocation Dynamics simulations of dislocation transport during sliding." Acta Materialia 156 (September 2018): 215–27. http://dx.doi.org/10.1016/j.actamat.2018.06.002.

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7

Zhao, Yue, Lucile Dezerald, and Jaime Marian. "Electronic Structure Calculations of Oxygen Atom Transport Energetics in the Presence of Screw Dislocations in Tungsten." Metals 9, no. 2 (February 20, 2019): 252. http://dx.doi.org/10.3390/met9020252.

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Plastic flow in body-centered cubic (bcc) alloys is governed by the thermally-activated motion of screw dislocations in close-packed planes. In bcc interstitial solid solutions, solute diffusion can occur at very fast rates owing to low migration energies and solute concentrations. Under mechanical loading, solutes may move on the same or similar time scale as dislocations glide, even at low temperatures, potentially resulting in very rich co-evolution processes that may have important effects in the overall material response. It is therefore important to accurately quantify the coupling between interstitial impurities and dislocations, so that larger-scale models can correctly account for their interactions. In this paper, we use electronic structure calculations to obtain the energetics of oxygen diffusion under stress and its interaction energy with screw dislocation cores in bcc tungsten. We find that oxygen atoms preferentially migrate from tetrahedral to tetrahedral site with an energy of 0.2 eV. This energy couples only weakly to hydrostatic and deviatoric deformations, with activation volumes of less than 0.02 and 0.02 b 3 , respectively. The strongest effect is found for the inelastic interaction between O atoms and screw dislocation cores, which leads to attractive energies between 1.2 and 1.9 eV and sometimes triggers a transformation of the screw dislocation core from an easy core configuration to a hard core configuration.

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8

Oktyabrsky, S., R. Kalyanaraman, K. Jagannadham, and J. Narayan. "Dislocation structure of low-angle grain boundaries in YBa2Cu3O7−δ/MgO films." Journal of Materials Research 14, no. 7 (July 1999): 2764–72. http://dx.doi.org/10.1557/jmr.1999.0369.

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Grain boundaries in laser-deposited YBa2Cu3O7−δ (YBCO)/MgO thin films have been investigated by high-resolution transmission electron microscopy. The films exhibit perfect texturing with YBCO(001)/MgO(001) giving rise to low-angle [001] tilt grain boundaries resulting from the grains with the c axis normal to the substrate surface and with misorientation in the a-b plane. The atomic structure of the grain boundaries was analyzed by using a dislocation model. Low-angle grain boundaries have been found to be aligned along (100) and (110) interface planes. For the (110) boundary plane, the low-energy dislocation configuration was found to consist of an array of alternating [100] and [010] dislocations. We have calculated the energy of various configurations and shown that the energy of the (110) boundary with dissociated dislocations is comparable to that of the (100) boundary, which explains the coexistence of (100) and (110) interface facets along the boundary. We have also modeled critical current transport through grain boundaries with various structures and found that the low-energy (110) grain boundary with dissociated dislocation array is expected to transport a lower superconducting current (by 25% for 6° misorientation) than (100) boundaries.

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9

Dalmau, Rafael, Jeffrey Britt, Hao Yang Fang, Balaji Raghothamachar, Michael Dudley, and Raoul Schlesser. "X-Ray Topography Characterization of Large Diameter AlN Single Crystal Substrates." Materials Science Forum 1004 (July 2020): 63–68. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.63.

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Large diameter aluminum nitride (AlN) substrates, up to 50 mm, were manufactured from single crystal boules grown by physical vapor transport (PVT). Synchrotron-based x-ray topography (XRT) was used to characterize the density, distribution, and type of dislocations. White beam topography images acquired in transmission geometry were used to analyze basal plane dislocations (BPDs) and low angle grain boundaries (LAGBs), while monochromatic beam, grazing incidence images were used to analyze threading dislocations. Boule diameter expansion, without the introduction of LAGBs around the periphery, was shown. A 48 mm substrate with a uniform threading dislocation density below 7.0 x 102 cm-2 and a BPD of 0 cm-2, the lowest dislocation densities reported to date for an AlN single crystal this size, was demonstrated.

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10

Wulfinghoff, Stephan, Vedran Glavas, and Thomas Böhlke. "Dislocation Transport in Single Crystals and Dislocation-based Micromechanical Hardening." PAMM 11, no. 1 (December 2011): 449–50. http://dx.doi.org/10.1002/pamm.201110216.

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11

Dudley, Michael, Huan Huan Wang, Fang Zhen Wu, Sha Yan Byrapa, Balaji Raghothamachar, Gloria Choi, Edward K. Sanchez, et al. "Formation Mechanism of Stacking Faults in PVT 4H-SiC Created by Deflection of Threading Dislocations with Burgers Vector c+a." Materials Science Forum 679-680 (March 2011): 269–72. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.269.

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Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of seventy-six millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels [1]. In this paper, detailed topography analysis will be presented of the deflection of threading dislocations with Burgers vectors of c and c+a onto the basal plane leading to reductions of the density of such dislocations down to levels of ~187 cm-2. The deflection of the latter type of dislocations produces complex faulted defect configurations and models for their creation are presented and discussed.

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12

Upadhyay, Manas Vijay, and Jérémy Bleyer. "Dislocation transport using a time-explicit Runge–Kutta discontinuous Galerkin finite element approach." Modelling and Simulation in Materials Science and Engineering 30, no. 3 (February 21, 2022): 034002. http://dx.doi.org/10.1088/1361-651x/ac44a7.

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Abstract A time-explicit Runge–Kutta discontinuous Galerkin (RKDG) finite element scheme is proposed to solve the dislocation transport initial boundary value problem in 3D. The dislocation density transport equation, which lies at the core of this problem, is a first-order unsteady-state advection–reaction-type hyperbolic partial differential equation; the DG approach is well suited to solve such equations that lack any diffusion terms. The development of the RKDG scheme follows the method of lines approach. First, a space semi-discretization is performed using the DG approach with upwinding to obtain a system of ordinary differential equations in time. Then, time discretization is performed using explicit RK schemes to solve this system. The 3D numerical implementation of the RKDG scheme is performed for the first-order (forward Euler), second-order and third-order RK methods using the strong stability preserving approach. These implementations provide (quasi-)optimal convergence rates for smooth solutions. A slope limiter is used to prevent spurious Gibbs oscillations arising from high-order space approximations (polynomial degree ⩾ 1) of rough solutions. A parametric study is performed to understand the influence of key parameters of the RKDG scheme on the stability of the solution predicted during a screw dislocation transport simulation. Then, annihilation of two oppositely signed screw dislocations and the expansion of a polygonal dislocation loop are simulated. The RKDG scheme is able to resolve the shock generated during dislocation annihilation without any spurious oscillations and predict the prismatic loop expansion with very low numerical diffusion. These results indicate that the proposed scheme is more robust and accurate in comparison to existing approaches based on the continuous Galerkin finite element method or the fast Fourier transform method.

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13

Raghothamachar, Balaji, Yu Yang, Rafael Dalmau, Baxter Moody, H. Spalding Craft, Raoul Schlesser, Michael Dudley, and Zlatko Sitar. "Defect Generation Mechanisms in PVT-Grown AlN Single Crystal Boules." Materials Science Forum 740-742 (January 2013): 91–94. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.91.

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A systematic study on the density and distribution of extended defects in a typical single crystal AlN boule grown by the physical vapor transport (PVT) method has been carried out in order to gain a detailed understanding of the formation of defects such as dislocations and low angle grain boundaries (LAGBs). Boule surface studies reveal that LAGBs are nucleated during initial stages of growth and propagate to the end of growth. Basal plane dislocations (BPDs) are generated during growth due to thermal gradient stresses. Higher BPD densities are found near the LAGBs at the boule edges due to additional stresses from constrained growth. Threading edge dislocations (TEDs) are typically replicated from the seed, and LAGBs composed of arrays of threading dislocation walls are formed to accommodate the c-axis rotation between different groups of threading screw dislocation (TSD) mediated growth centers.

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14

Wu, Fang Zhen, Huan Huan Wang, Sha Yan Byrapa, Balaji Raghothamachar, Michael Dudley, Edward K. Sanchez, Darren M. Hansen, Roman Drachev, Stephan G. Mueller, and Mark J. Loboda. "Synchrotron X-Ray Topography Studies of the Propagation and Post-Growth Mutual Interaction of Threading Growth Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC." Materials Science Forum 717-720 (May 2012): 343–46. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.343.

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Synchrotron White Beam X-ray Topography (SWBXT) imaging of wafers cut parallel to the growth axis from 4H-SiC boules grown using Physical Vapor Transport has enabled visualization of the evolution of the defect microstructure. Here we present observations of the propagation and post-growth mutual interaction of threading growth dislocations with c-component of Burgers vector. Detailed contrast extinction studies reveal the presence of two types of such dislocations: pure c-axis screw dislocations and those with Burgers Vector n1c+n2a, where n1is equal to 1 and n2is equal to 1 or 2. In addition, observations of dislocation propagation show that some of the threading dislocations with c-component of Burgers adopt a curved, slightly helical morphology which can drive the dislocations from adjacent nucleation sites together enabling them to respond to the inter-dislocation forces and react. Since all of the dislocations exhibiting such helical configurations have significant screw component, and in view of the fact that such dislocations are typically not observed to glide, it is believed that such morphologies result in large part from the interaction of a non-equilibrium concentration of vacancies with the originally approximately straight dislocation cores during post-growth cooling. Such interactions can lead to complete or partial Burgers vector annihilation. Among the reactions observed are: (a) the reaction between opposite-sign threading screw dislocations with Burgers vectors c and –c wherein some segments annihilate leaving others in the form of trails of stranded loops comprising closed dislocation dipoles; (b) the reaction between threading dislocations with Burgers vectors of -c+a and c+a wherein the opposite c-components annihilate leaving behind the two a-components; (c) the similar reaction between threading dislocations with Burgers vectors of -c and c+a leaving behind the a-component.

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15

Dogge, M. M. W., R. H. J. Peerlings, and M. G. D. Geers. "Interface modeling in continuum dislocation transport." Mechanics of Materials 88 (September 2015): 30–43. http://dx.doi.org/10.1016/j.mechmat.2015.04.007.

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16

Wulfinghoff, Stephan, and Thomas Böhlke. "Gradient crystal plasticity including dislocation-based work-hardening and dislocation transport." International Journal of Plasticity 69 (June 2015): 152–69. http://dx.doi.org/10.1016/j.ijplas.2014.12.003.

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17

Filatov, A., A. Pogorelov, D. Kropachev, and O. Dmitrichenko. "Dislocation Mass-Transfer and Electrical Phenomena in Metals under Pulsed Laser Influence." Defect and Diffusion Forum 363 (May 2015): 173–77. http://dx.doi.org/10.4028/www.scientific.net/ddf.363.173.

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The influence of moving dislocations on mass-transfer and the phenomena, accompanying it in pulse-deformed metals is studied in a real-time. Transport of self-interstitial atoms (SIAs) by mobile edge dislocations in crystal with FCC lattice is investigated by molecular dynamics. A strain rate (106s-1) and dislocation density (1010– 1012cm-2) in simulated crystal corresponds to a laser effect in a Q-factor mode. The experimental investigations in a real-time are performed by recording of electrical signal induced by the laser pulse irradiation of metal foils of different crystal structures.

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18

Wang, Ding, Ping Wang, Shubham Mondal, Yixin Xiao, Mingtao Hu, and Zetian Mi. "Impact of dislocation density on the ferroelectric properties of ScAlN grown by molecular beam epitaxy." Applied Physics Letters 121, no. 4 (July 25, 2022): 042108. http://dx.doi.org/10.1063/5.0099913.

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We report on the effect of dislocation density on the ferroelectric properties of single-crystalline ScAlN thin films grown by molecular beam epitaxy. Wurtzite phase and atomically smooth ScAlN films have been grown on bulk GaN, GaN on sapphire, and GaN on Si substrates with dislocation densities ranging from ∼107 to 1010 cm−2. Despite the significant difference in dislocation density, ferroelectricity is observed in all three samples. The presence of high densities of dislocations, however, results in enhanced asymmetric P–E loops and overestimated remnant polarization values. Further measurements show that the leakage current and breakdown strength can be improved with decreasing dislocation density. Detailed studies suggest that trapping/detrapping assisted transport is the main leakage mechanism in epitaxial ferroelectric ScAlN films. This work sheds light on the essential material quality considerations for tuning the ferroelectric property of ScAlN toward integration with mainstream semiconductor platforms, e.g., Si, and paves the way for next-generation electronics, optoelectronics, and piezoelectronics.

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19

Gao, Yu Qiang, Hong Yan Zhang, Yan Min Zong, Huan Huan Wang, Jian Qiu Guo, Balaji Raghothamachar, Michael Dudley, and Xi Jie Wang. "150 mm 4H-SiC Substrate with Low Defect Density." Materials Science Forum 858 (May 2016): 41–44. http://dx.doi.org/10.4028/www.scientific.net/msf.858.41.

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150 mm diameter 4H-SiC boules were grown by the physical vapor transport (PVT) method. Synchrotron white beam X-ray topography (SWBXT) was carried out to investigate the distribution of defects in axial slices cut from the boule. It was found that an increase of dislocations and micropipes was mainly induced by inclusions. After eliminating these inclusions, which were formed in the mid to late stage of the crystal growth, both the screw dislocation density and base plane dislocation density could be decreased down to a magnitude of 102 cm-2, which is comparable to that of high quality 100 mm diameter SiC substrates.

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20

Turlo, Vladyslav. "Dislocations as a Tool for Nanostructuring Advanced Materials." Physchem 1, no. 3 (September 26, 2021): 225–31. http://dx.doi.org/10.3390/physchem1030016.

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Dislocations present unique opportunities for nanostructuring advanced structural and functional materials due to the recent discoveries of linear complexions thermodynamically stable nanoscale features with unique chemistry and structure confined at dislocations. The formation of such features is driven by solute segregation near the dislocation core and results in the stabilization of dislocations, altering mechanical, thermodynamic, and transport properties of the final material. This perspective article gives an overview of the recent discoveries and predictions made by high-resolution experimental characterization techniques, as well as large-scale atomistic simulations in the newly emerging field of linear complexions.

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21

Johnson, J. N. "Dislocation transport in shock‐loaded single crystals." Applied Physics Letters 50, no. 1 (January 5, 1987): 28–30. http://dx.doi.org/10.1063/1.98116.

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22

Chen, Yi, Ning Zhang, Xian Rong Huang, David R. Black, and Michael Dudley. "Studies of the Distribution of Elementary Threading Screw Dislocations in 4H Silicon Carbide Wafer." Materials Science Forum 600-603 (September 2008): 301–4. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.301.

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The density and sense distribution of elementary threading screw dislocations in a physical vapor transport grown 3-inch 4H silicon carbide wafer have been studied. The density of TSDs ranges between 1.6×103/cm2 and 7.1×103/cm2 and the lowest density is observed at positions approximately half radius off the wafer center. The dislocation sense of elementary threading screw dislocations can be readily revealed by the asymmetric contrast of their images in grazing-incidence x-ray topographs using pyramidal plane reflections. The circumferential and radial distributions of the sense of elementary threading screw dislocations have been studied and no clear trends are observed in either distribution.

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23

Pu, S. D., and S. W. Ooi. "Hydrogen transport by dislocation movement in austenitic steel." Materials Science and Engineering: A 761 (July 2019): 138059. http://dx.doi.org/10.1016/j.msea.2019.138059.

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24

Hwang, C., and I. M. Bernstein. "Dislocation transport of hydrogen in iron single crystals." Acta Metallurgica 34, no. 6 (June 1986): 1001–10. http://dx.doi.org/10.1016/0001-6160(86)90209-9.

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25

Raghothamachar, Balaji, Rafael Dalmau, Baxter Moody, H. Spalding Craft, Raoul Schlesser, Jin Qiao Xie, Ramón Collazo, Michael Dudley, and Zlatko Sitar. "Low Defect Density Bulk AlN Substrates for High Performance Electronics and Optoelectronics." Materials Science Forum 717-720 (May 2012): 1287–90. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.1287.

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Using the physical vapor transport (PVT) method, single crystal boules of AlN have been grown and wafers sliced from them have been characterized by synchrotron white beam X-ray topography (SWBXT) in conjunction with optical microscopy. X-ray topographs reveal that the wafers contain dislocations that are inhomogeneously distributed with densities varying from as low as 0 cm-2 to as high as 104 cm-2. Two types of dislocations have been identified: basal plane dislocations and threading dislocations, both having Burgers vectors of type 1/3<112-0> indicating that their origin is likely due to post-growth deformation. In some cases, the dislocations are arranged in low angle grain boundaries. However, large areas of the wafers are nearly dislocation-free and section X-ray topographs of these regions reveal the high crystalline perfection.

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26

Fressengeas, Claude, and Vincent Taupin. "Revisiting the Application of Field Dislocation and Disclination Mechanics to Grain Boundaries." Metals 10, no. 11 (November 16, 2020): 1517. http://dx.doi.org/10.3390/met10111517.

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We review the mechanical theory of dislocation and disclination density fields and its application to grain boundary modeling. The theory accounts for the incompatibility of the elastic strain and curvature tensors due to the presence of dislocations and disclinations. The free energy density is assumed to be quadratic in elastic strain and curvature and has nonlocal character. The balance of loads in the body is described by higher-order equations using the work-conjugates of the strain and curvature tensors, i.e., the stress and couple-stress tensors. Conservation statements for the translational and rotational discontinuities provide a dynamic framework for dislocation and disclination motion in terms of transport relationships. Plasticity of the body is therefore viewed as being mediated by both dislocation and disclination motion. The driving forces for these motions are identified from the mechanical dissipation, which provides guidelines for the admissible constitutive relations. On this basis, the theory is expressed as a set of partial differential equations where the unknowns are the material displacement and the dislocation and disclination density fields. The theory is applied in cases where rotational defects matter in the structure and deformation of the body, such as grain boundaries in polycrystals and grain boundary-mediated plasticity. Characteristic examples are provided for the grain boundary structure in terms of periodic arrays of disclination dipoles and for grain boundary migration under applied shear.

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27

Sai, P. O., N. V. Safryuk-Romanenko, D. B. But, G. Cywiński, N. S. Boltovets, P. N. Brunkov, N. V. Jmeric, S. V. Ivanov, and V. V. Shynkarenko. "Features of the Formation of Ohmic Contacts to n+-InN." Ukrainian Journal of Physics 64, no. 1 (January 30, 2019): 56. http://dx.doi.org/10.15407/ujpe64.1.56.

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We report about a study of the formation and current transport mechanism of ohmic contacts to n+-InN with electron concentrations of 2×1018, 8×1018, and 4×1019 cm−3. Pd/Ti/Au ohmic contacts are formed by the proposed approach of simultaneous magnetron metal deposition and in-situ temperature annealing, which allows obtaining a low contact resistivity (4.20±2.67)×10−6 Ohm· cm2. The additional rapid thermal annealing in the temperature interval 350–400 ∘C is used to improve further contact characteristics. Optimal parameters of the temperature treatment are determined by statistic methods. As for the current transport mechanism, the unusual growing temperature behavior of contact resistivity is observed in the wide temperature range 4.2–380K for each doping level of InN films. The mechanism of thermionic current flow explains the current transport through metal shunts, which is associated with the conducting dislocations. The extracted density of conducting metal shunts has a good agreement with experimental values of the screw and edge dislocation densities experimentally obtained by high-resolution X-ray diffraction. Additionally, from the obtained contact resistivity temperature dependences, we can argue about the metal, which penetrates dislocations and forms shunts.

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28

Wicht, Thomas, Stephan Müller, Roland Weingärtner, Boris Epelbaum, Sven Besendörfer, Ulrich Bläß, Matthias Weisser, Tobias Unruh, and Elke Meissner. "X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals." Journal of Applied Crystallography 53, no. 4 (July 30, 2020): 1080–86. http://dx.doi.org/10.1107/s1600576720008961.

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AlN slices from bulk crystals grown under low thermomechanical stress conditions via the physical vapor transport (PVT) method were analyzed by X-ray methods to study the influence of the growth mode on the crystal quality. Defect types and densities were analyzed along axial [0001] as well as lateral growth directions. X-ray diffraction (0110) rocking-curve mappings of representative wafer cuts reveal a low mean FWHM of 13.4 arcsec, indicating the generally high crystal quality. The total dislocation density of 2 × 103 cm−2 as determined by X-ray topography is low and dislocations are largely threading edge dislocations of b = 1/3〈1120〉 type. The absence of basal plane dislocations in homogeneous crystal regions void of macroscopic defects can be linked to the low-stress growth conditions. Under the investigated growth conditions this high crystal quality can be maintained both along the axial [0001] direction and within lateral growth directions. Exceptions to this are some locally confined, misoriented grains and defect clusters, most of which are directly inherited from the seed or are formed due to the employed seed fixation technique on the outer periphery of the crystals. Seed-shaping experiments indicate no apparent kinetic limitations for an enhanced lateral expansion rate and the resulting crystal quality, specifically with regard to the growth mode on a-face facets.

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29

Traynelis, Vincent C., Gary D. Marano, Ralph O. Dunker, and Howard H. Kaufman. "Traumatic atlanto-occipital dislocation." Journal of Neurosurgery 65, no. 6 (December 1986): 863–70. http://dx.doi.org/10.3171/jns.1986.65.6.0863.

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✓ Traumatic atlanto-occipital dislocation is a serious injury that is usually fatal. The number of patients surviving this injury, however, appears to be increasing, and most of these survivors are children. This may reflect an improvement in emergency transport services. Seventeen previously reported cases of patients surviving atlanto-occipital dislocation for more than 48 hours are reviewed and an additional case is presented. Many of these patients had an excellent neurological outcome. The radiographic criteria necessary for the diagnosis of atlanto-occipital dislocation are discussed. Cervical computerized tomography may confirm the diagnosis when necessary. It is suggested that there are three types of atlanto-occipital dislocation; utilizing this new classification, a rationale for treatment is described. Fusion is favored for long-term stability.

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30

Milosevic, Boban, and Vasilije Miskovic. "Choice of sites and means of transport for dislocation." Vojnotehnicki glasnik 51, no. 4-5 (2003): 433–46. http://dx.doi.org/10.5937/vojtehg0305433m.

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Haegel, Nancy M., Scott E. Williams, C. Frenzen, and C. Scandrett. "Imaging charge transport and dislocation networks in ordered GaInP." Physica B: Condensed Matter 404, no. 23-24 (December 2009): 4963–66. http://dx.doi.org/10.1016/j.physb.2009.08.219.

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32

Varadhan, S. N., A. J. Beaudoin, A. Acharya, and C. Fressengeas. "Dislocation transport using an explicit Galerkin/least-squares formulation." Modelling and Simulation in Materials Science and Engineering 14, no. 7 (September 27, 2006): 1245–70. http://dx.doi.org/10.1088/0965-0393/14/7/011.

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WALGRAEF, D. "Reaction-transport dynamics and dislocation patterns in deformed materials." Earth-Science Reviews 29, no. 1-4 (October 1990): 299–308. http://dx.doi.org/10.1016/0012-8252(90)90044-v.

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34

Yang, Long, Li Xia Zhao, Hui Wang Wu, Yafei Liu, Tuerxun Ailihumaer, Balaji Raghothamachar, and Michael Dudley. "Characterization and Reduction of Defects in 4H-SiC Substrate and Homo-Epitaxial Wafer." Materials Science Forum 1004 (July 2020): 387–92. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.387.

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4H-SiC substrates and homo-epitaxial layers were obtained using the traditional methods of physical vapor transport and chemical vapor deposition. Defect morphology has been studied using both Synchrotron White Beam X-ray Topography and Monochromatic Beam X-ray Topography. Molten KOH etching method was adopted to further investigate the dislocation behavior mechanisms. Deflected dislocations were observed at the periphery regions in both substrate and epitaxial wafers. 3C polytypes and half loop arrays were observed in the 4H-SiC epitaxial wafer. It is also found that the majority of basal plane dislocations are converted to threading edge dislocations in the epitaxial wafer samples. The proportion of BPD to TED conversion depends on the surface step morphology and growth mode in epitaxial growth which in turn depends on the C/Si ratio. By the optimization of etching time prior to epitaxy and C/Si ratio, high-quality epitaxial wafers with extremely low basal plane dislocations densities (＜0.1 cm-2) was obtained.

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35

Restuccia, Liliana. "Non-equilibrium temperatures and heat transport in nanosystems with defects, described by a tensorial internal variable." Communications in Applied and Industrial Mathematics 7, no. 2 (June 1, 2016): 81–97. http://dx.doi.org/10.1515/caim-2016-0007.

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AbstractThe paper deals with the meaning of non-equilibrium temperatures in nanosystems with an internal variable, describing defects inside them, and implications on heat transport. In equilibrium all definitions of temperature lead to the same value, but in nonequilibrium steady states they lead to different values, giving information on different degrees of freedom. We discuss the caloric and entropic non-equilibrium temperatures and the relations among them, in defective nanosystems (crystals with dislocations or porous channels, carbon nanotubes in a solid matrix and so on), crossed by an external energy flux. Here, we present a model for nanocrystals with dislocation defects submitted to an external energy flux. The dislocations may have a strong influence on the effective thermal conductivity, and their own dynamics may be coupled in relevant way to the heat flux dynamics. In the linear case the constitutive relations, the rate equations for the internal variable and the heat flux are worked out and a generalized telegraphic heat equation is derived in the anisotropic and isotropic case, describing the thermal disturbances with finite velocity.

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36

Roy, A., S. Puri, and A. Acharya. "Phenomenological mesoscopic field dislocation mechanics, lower-order gradient plasticity, and transport of mean excess dislocation density." Modelling and Simulation in Materials Science and Engineering 15, no. 1 (December 7, 2006): S167—S180. http://dx.doi.org/10.1088/0965-0393/15/1/s14.

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37

Liu, Zihang, Xianfu Meng, Dandan Qin, Bo Cui, Haijun Wu, Yang Zhang, Stephen J. Pennycook, Wei Cai, and Jiehe Sui. "New insights into the role of dislocation engineering in N-type filled skutterudite CoSb3." Journal of Materials Chemistry C 7, no. 43 (2019): 13622–31. http://dx.doi.org/10.1039/c9tc03839f.

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38

Bonilla, Daniel, Enrique Muñoz, and Rodrigo Soto-Garrido. "Thermo-Magneto-Electric Transport through a Torsion Dislocation in a Type I Weyl Semimetal." Nanomaterials 11, no. 11 (November 5, 2021): 2972. http://dx.doi.org/10.3390/nano11112972.

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Herein, we study electronic and thermoelectric transport in a type I Weyl semimetal nanojunction, with a torsional dislocation defect, in the presence of an external magnetic field parallel to the dislocation axis. The defect is modeled in a cylindrical geometry, as a combination of a gauge field accounting for torsional strain and a delta-potential barrier for the lattice mismatch effect. In the Landauer formalism, we find that due to the combination of strain and magnetic field, the electric current exhibits chiral valley-polarization, and the conductance displays the signature of Landau levels. We also compute the thermal transport coefficients, where a high thermopower and a large figure of merit are predicted for the junction.

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Kim, Jae‐Hwan, Young‐Hwan Lee, Jun‐Hyoung Park, Byeong‐Joo Lee, Young‐Woon Byeon, and Jae‐Chul Lee. "Ultrafast Na Transport into Crystalline Sn via Dislocation‐Pipe Diffusion." Small 18, no. 2 (November 21, 2021): 2104944. http://dx.doi.org/10.1002/smll.202104944.

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Hernández, H., T. J. Massart, R. H. J. Peerlings, and M. G. D. Geers. "Towards an unconditionally stable numerical scheme for continuum dislocation transport." Modelling and Simulation in Materials Science and Engineering 23, no. 8 (October 26, 2015): 085013. http://dx.doi.org/10.1088/0965-0393/23/8/085013.

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41

Rezaei Mianroodi, Jaber, Ron Peerlings, and Bob Svendsen. "Strongly non-local modelling of dislocation transport and pile-up." Philosophical Magazine 96, no. 12 (March 16, 2016): 1171–87. http://dx.doi.org/10.1080/14786435.2016.1157270.

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Nitta, Shugo, Michihiko Kariya, Takayuki Kashima, Shigeo Yamaguchi, Hiroshi Amano, and Isamu Akasaki. "Mass transport and the reduction of threading dislocation in GaN." Applied Surface Science 159-160 (June 2000): 421–26. http://dx.doi.org/10.1016/s0169-4332(00)00089-1.

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Sato, T., T. Suzuki, S. Tomiya, and S. Yamada. "Dislocation-limited electron transport in InSb grown on GaAs(001)." Physica B: Condensed Matter 376-377 (April 2006): 579–82. http://dx.doi.org/10.1016/j.physb.2005.12.146.

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Murphy, J. D., S. Senkader, R. J. Falster, and P. R. Wilshaw. "Oxygen transport in Czochralski silicon investigated by dislocation locking experiments." Materials Science and Engineering: B 134, no. 2-3 (October 2006): 176–84. http://dx.doi.org/10.1016/j.mseb.2006.06.045.

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45

Xie, Ruiwen, Song Lu, Wei Li, Yanzhong Tian, and Levente Vitos. "Dissociated dislocation-mediated carbon transport and diffusion in austenitic iron." Acta Materialia 191 (June 2020): 43–50. http://dx.doi.org/10.1016/j.actamat.2020.03.042.

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46

Hanisch-Blicharski, Anja, Boris Krenzer, Simone Wall, Annika Kalus, Tim Frigge, and Michael Horn-von Hoegen. "Heat transport through interfaces with and without misfit dislocation arrays." Journal of Materials Research 27, no. 21 (October 15, 2012): 2718–23. http://dx.doi.org/10.1557/jmr.2012.316.

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47

Solomon, Gemma C., Josh Vura-Weis, Carmen Herrmann, Michael R. Wasielewski, and Mark A. Ratner. "Understanding Coherent Transport through π-Stacked Systems upon Spatial Dislocation†." Journal of Physical Chemistry B 114, no. 45 (November 18, 2010): 14735–44. http://dx.doi.org/10.1021/jp103110h.

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48

Feng, Qian, Peng Shi, Jie Zhao, Kai Du, Yu Kun Li, Qing Feng, and Yue Hao. "Transport Properties of Two-Dimensional Electron Gas in Cubic AlGaN/GaN Heterostructures." Advanced Materials Research 873 (December 2013): 777–82. http://dx.doi.org/10.4028/www.scientific.net/amr.873.777.

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We presented a theoretical study of the dependence of 2DEG mobility on temperature, barrier thickness, Al content, donor concentration to reveal the internal physics of 2DEG mobility in cubic AlGaN/GaNheterostructures. The 2DEG mobility is modeled as a combined effect of the scattering mechanisms including acoustic phonons, ionized impurity, dislocation, alloy disorder and interface roughness scattering.The variation of mobility results mainly from the change of 2DEG density and temperature. It reveals the dominant scattering mechanismsare dislocation and alloy disorder scattering atlow temperature.Acoustic phonons scattering becomes the major limit at 300k. Impurity scattering plays the key role when donor density rises. We find a maximum mobility with a structure of 25% Al content and 4-5nm barrier thickness.

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49

Camus, G. M., D. J. Duquette, and N. S. Stoloff. "Effect of an oxide dispersion on the hydrogen embrittlement of a Ni3Al base alloy." Journal of Materials Research 5, no. 5 (May 1990): 950–54. http://dx.doi.org/10.1557/jmr.1990.0950.

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The susceptibility of a hot isostatically pressed Ni3AI, Cr, Zr alloy to hydrogen embrittlement has been studied. The base alloy and a second alloy containing 5 vol. % Y2O3 particles were tested by cathodically charging with hydrogen prior to or simultaneously with tensile testing. Embrittlement of both alloys was noted under both charging conditions, but was much more severe for simultaneous charging. Intergranular fracture due to hydrogen was noted in the base alloy, while the dispersoid-containing alloy failed along prior particle boundaries. The results are explained by a dislocation transport mechanism in which hydrogen is delivered to interior fracture sites by mobile dislocations. Much greater penetration of hydrogen is achieved under simultaneous charging conditions.

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50

Song, Xueyan. "(110) facets and dislocation structure of low-angle grain boundaries in YBa2Cu3O7−δ and Y0.7Ca0.3Ba2Cu3O7−δ thin film bicrystals." Journal of Materials Research 22, no. 4 (April 2007): 950–57. http://dx.doi.org/10.1557/jmr.2007.0110.

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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.

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