scholarly journals Investigation of the Grain Boundary Character and Dislocation Density of Different Types of High Performance Multicrystalline Silicon

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 341 ◽  
Author(s):  
Gaute Stokkan ◽  
Adolphus Song ◽  
Birgit Ryningen
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Performance ◽  
Coincidence Site Lattice ◽  
Grain Structure ◽  
Multicrystalline Silicon ◽  
Initial Growth ◽  
Cluster Density ◽  
Dislocation Cluster

Wafers from three heights and two different lateral positions (corner and centre) of four industrial multicrystalline silicon ingots were analysed with respect to their grain structure and dislocation density. Three of the ingots were non-seeded and one ingot was seeded. It was found that there is a strong correlation between the ratio of the densities of (coincidence site lattice) CSL grain boundaries and high angle grain boundaries in the bottom of a block and the dislocation cluster density higher in the block. In general, the seeded blocks, both the corner and centre block, have a lower dislocation cluster density than in the non-seeded blocks, which displayed a large variation. The density of the random angle boundaries in the corner blocks of the non-seeded ingots was similar to the density in the seeded ingots, while the density in the centre blocks was lower. However, the density of CSL boundaries was higher in all the non-seeded than in the seeded ingots. It appears that both of these grain boundary densities influence the presence of dislocation clusters, and we propose they act as dislocation sinks and sources, respectively. The ability to generate small grain size material without seeding appears to be correlated to the morphology of the coating, which is generally rougher in the corner positions than in the middle. Furthermore, the density of twins and CSL boundaries depends on the growth mode during initial growth and thus on the degree of supercooling. Controlling both these properties is important in order to be able to successfully produce uniform quality high-performance multicrystalline silicon by the advantageous non-seeding method.

Observations of dislocation interactions with recrystallized grain boundaries

1988 ◽  
Vol 46 ◽  
pp. 628-629
Author(s):  
C. W. Price
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Hot Deformation ◽  
Static Recrystallization ◽  
High Dislocation Density ◽  
High Angle ◽  
Dislocation Interactions

Little evidence exists on the interaction of individual dislocations with recrystallized grain boundaries, primarily because of the severely overlapping contrast of the high dislocation density usually present during recrystallization. Interesting evidence of such interaction, Fig. 1, was discovered during examination of some old work on the hot deformation of Al-4.64 Cu. The specimen was deformed in a programmable thermomechanical instrument at 527 C and a strain rate of 25 cm/cm/s to a strain of 0.7. Static recrystallization occurred during a post anneal of 23 s also at 527 C. The figure shows evidence of dissociation of a subboundary at an intersection with a recrystallized high-angle grain boundary. At least one set of dislocations appears to be out of contrast in Fig. 1, and a grainboundary precipitate also is visible. Unfortunately, only subgrain sizes were of interest at the time the micrograph was recorded, and no attempt was made to analyze the dislocation structure.

Realization of Bulk Multicrystalline Silicon with Controlled Grain Boundaries by Utilizing Spontaneous Modification of Grain Boundary Configuration

2006 ◽  
Vol 45 (3A) ◽  
pp. 1734-1737 ◽  
Author(s):  
Noritaka Usami ◽  
Kentaro Kutsukake ◽  
Takamasa Sugawara ◽  
Kozo Fujiwara ◽  
Wugen Pan ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Multicrystalline Silicon

scholarly journals Texture Evolution in AA6082-T6 BFSW Welds: Optical Microscopy and EBSD Characterisation

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3215 ◽  
Author(s):  
Abbas Tamadon ◽  
Dirk J. Pons ◽  
Don Clucas ◽  
Kamil Sued
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Optical Microscopy ◽  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Grain Structure ◽  
Friction Stir ◽  
Fine Grain ◽  
Grain Structures ◽  
Dynamic Recrystallisation

One of the difficulties with bobbin friction stir welding (BFSW) has been the visualisation of microstructure, particularly grain boundaries, and this is especially problematic for materials with fine grain structure, such as AA6082-T6 aluminium as here. Welds of this material were examined using optical microscopy (OM) and electron backscatter diffraction (EBSD). Results show that the grain structures that form depend on a complex set of factors. The motion of the pin and shoulder features transports material around the weld, which induces shear. The shear deformation around the pin is non-uniform with a thermal and strain gradient across the weld, and hence the dynamic recrystallisation (DRX) processes are also variable, giving a range of observed polycrystalline and grain boundary structures. Partial DRX was observed at both hourglass boundaries, and full DRX at mid-stirring zone. The grain boundary mapping showed the formation of low-angle grain boundaries (LAGBs) at regions of high shear as a consequence of thermomechanical nature of the process.

scholarly journals Segregation of P and S Impurities to A Σ9 Grain Boundary in Cu

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1362
Author(s):  
Cláudio M. Lousada ◽  
Pavel A. Korzhavyi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Coordination Number ◽  
High Performance ◽  
Chemical Properties ◽  
Atomic Scale ◽  
Atomic Site ◽  
Segregation Energy ◽  
Physical Chemical ◽  
Symmetric Tilt

The segregation of P and S to grain boundaries (GBs) in fcc Cu has implications in diverse physical-chemical properties of the material and this can be of particular high relevance when the material is employed in high performance applications. Here, we studied the segregation of P and S to the symmetric tilt Σ9 (22¯1¯) [110], 38.9° GB of fcc Cu. This GB is characterized by a variety of segregation sites within and near the GB plane, with considerable differences in both atomic site volume and coordination number and geometry. We found that the segregation energies of P and S vary considerably both with distance from the GB plane and sites within the GB plane. The segregation energy is significantly large at the GB plane but drops to almost zero at a distance of only ≈3.5 Å from this. Additionally, for each impurity there are considerable variations in energy (up to 0.6 eV) between segregation sites in the GB plane. These variations have origins both in differences in coordination number and atomic site volume with the effect of coordination number dominating. For sites with the same coordination number, up to a certain atomic site volume, a larger atomic site volume leads to a stronger segregation. After that limit in volume has been reached, a larger volume leads to weaker segregation. The fact that the segregation energy varies with such magnitude within the Σ9 GB plane may have implications in the accumulation of these impurities at these GBs in the material. Because of this, atomic-scale variations of concentration of P and S are expected to occur at the Σ9 GB center and in other GBs with similar features.

Can Grain Boundaries Improve the Performance of Cu(In,Ga)Se2 Solar Cells?

2007 ◽  
Vol 1012 ◽  
Author(s):  
Uwe Rau ◽  
Uwe Rau
Keyword(s):  
Solar Cells ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Performance ◽  
Band Offset ◽  
Device Performance ◽  
Localized Defects ◽  
Recombination Centers ◽  
Numerical Device ◽  
Large Charge

AbstractTwo-dimensional numerical device simulations investigate the influence of grain boundaries on the performance of Cu(In,Ga)Se2 solar cells focussing on the question whether or not grain boundaries can improve the efficiency of those devices. The results unveil the following statements: (i) The mere introduction of a grain boundary by adding localized defects into a device that has a high performance from the beginning is not beneficial. (ii) Polycrystalline solar cells can outperform monocrystalline ones, if the total number of defects is equal in both devices. I.e. a given number of recombination centers is better dealt with if these defects are concentrated at the grain boundary rather than homogeneously distributed in the bulk. (iii) A significant improvement of carrier collection via the grain boundaries is found if the bulk of the devices is assumed as relatively poor. In this situation, addition of defects that are not much recombination ac-tive but provide a large charge density at the grain boundaries can improve the device performance. (iv) Passivation of grain boundaries by an internal band offset in the valence band is effective only if the internal barrier amounts at least to 300 meV.

The Morphology of Grain Boundary Interactions with Twins in YBa2Cu3O7−δ

1993 ◽  
Vol 319 ◽  
Author(s):  
Jenn-Yue Wang ◽  
A. H. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Twin Boundary ◽  
Interfacial Energy ◽  
Coincidence Site Lattice ◽  
The Other ◽  
Twin Boundaries ◽  
Site Lattice ◽  
Dislocation Arrays

AbstractVarious morphologies are observed where twins meet grain boundaries in YBa2Cu3O7−δ. Twins may be “correlated” at the boundary (i.e. twin boundaries from one grain may meet a twin boundary from the other grain in a quadruple junction) and the twins may be narrowed or “constricted” at the boundary. These effects are determined by the interfacial energy. We estimate the energy of the various interfaces by determining the dislocation arrays they contain, using the constrained coincidence site lattice (CCSL) model and Bollmann's O2-lattice formalism. Our approach indicates that there are significant changes in the energy of the interfaces and is thus able to explain the variety of observed morphologies.

Grain Boundary Characteristics Evaluation by Atomistic Investigation Methods

2009 ◽  
Vol 1215 ◽  
Author(s):  
Yoshiyuki Kaji ◽  
Tomohito Tsuru ◽  
Yoji Shibutani
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Density Functional ◽  
Coincidence Site Lattice ◽  
Individual Characteristics ◽  
Material Strength ◽  
Investigation Methods ◽  
Grain Boundary Characteristics ◽  
The Individual ◽  
Boundary Characteristics

AbstractThe grain boundary has been recognized for one of the major defect structures in determining the material strength. It is increasingly important to understand the individual characteristics of various types of grain boundaries due to the recent advances in material miniaturization technique.In the present study three types of grain boundaries of coincidence site lattice (CSL), small angle (SA), and random types are considered as the representative example of grain boundaries. The grain boundary energies and atomic configurations of CSL are first evaluated by first-principle density functional theory (DFT) and the embedded atom method (EAM) calculations. SA and random grain boundaries are subsequently constructed by the same EAM and the fundamental characteristics are investigated by the discrete dislocation mechanics models and the Voronoi polyhedral computational geometric method. As the result, it is found that the local structures are well accorded with the previously reported high resolution-transmission electron microscope (HR-TEM) observations, and that stress distributions of CSL and SA grain boundaries are localized around the grain boundary core. The random grain boundary shows extremely heterogeneous core structures including a lot of pentagon-shaped Voronoi polyhedral resulting from the amorphous-like structure.

Observations and implications of grain boundary dislocation networks in high-angle YBa2Cu3O7−δ grain boundaries

1990 ◽  
Vol 5 (5) ◽  
pp. 919-928 ◽  
Author(s):  
S. E. Babcock ◽  
D. C. Larbalestier
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Boundary Structure ◽  
High Angle ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Regular Networks

Regular networks of localized grain boundary dislocations (GBDs) have been imaged by means of transmission electron microscopy in three different types of high-angle grain boundaries in YBa2Cu3O7-δ, implying that these boundaries possess ordered structures upon which a significant periodic strain field is superimposed. The occurrence of these GBD networks is shown to be consistent with the GBD/Structural Unit and Coincidence Site Lattice (CSL)/Near CSL descriptions for grain boundary structure. Thus, these dislocations appear to be intrinsic features of the boundary structure. The spacing of the observed GBDs ranged from ∼10 nm to ∼100 nm. These GBDs make the grain boundaries heterogeneous on a scale that approaches the coherence length and may contribute to their weak-link character by producing the “superconducting micro-bridge” microstructure which has been suggested on the basis of detailed electromagnetic measurements on similar samples.

Grain-Focused Microstructure Simulations: Stress-Induced Evolution of Polycrystalline Films

2006 ◽  
Vol 45 ◽  
pp. 1178-1183
Author(s):  
Daniel N. Bentz ◽  
Max O. Bloomfield ◽  
Timothy S. Cale
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Level Sets ◽  
Boundary Migration ◽  
Grain Structure ◽  
Internal Stresses ◽  
Polycrystalline Films ◽  
Silicon Dioxide Film ◽  
Thermally Induced ◽  
Anisotropic Elastic

We discuss simulations of grain boundary motion utilizing a grain-continuum approach to representing polycrystalline films; i.e., as a system of distinct but interacting continua. Field variables are computed as functions of position in each grain; e.g., internal stresses and concentrations. Grain boundaries are represented and tracked using multiple level sets, providing a method to evolve the grain structure in time. We demonstrate the approach using stress-driven grain boundary migration in polycrystalline copper films, assuming that migration is due to vacancy migration. The anisotropic elastic constants of single crystal copper are used for each grain, under specified rotations (grain orientations). Stresses and stress gradients are thermally induced in a film with <111> texture, with the exception of a single <100> grain on a silicon dioxide film on a silicon substrate. Grain boundary velocities are calculated from the fluxes of vacancies to grain boundaries. The computed velocities are then used to update the level sets that represent the grain boundaries.

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