Investigating the Relationship Between Atomic Structure and Carrier Depletion at [001] tilt Grain Boundaries in Ybco

1999 ◽  
Vol 574 ◽  
Author(s):  
N. D. Browning ◽  
J. P. Buban
Keyword(s):  
Grain Boundaries ◽  
Structural Unit ◽  
Boundary Plane ◽  
Charge Carriers ◽  
Mobile Charge ◽  
Band Bending ◽  
Donor States ◽  
P Type ◽  
The Relationship ◽  
Theoretical Analyses

AbstractRecent theoretical analyses [1] have suggested that the origin of the reduced Jc at grain boundaries in high-Tc superconductors may be band bending, which results in the depletion of mobile charge carriers at the boundaries. For this to occur in these p-type superconductors there must, by definition, be a high density of localized donor states in the boundary plane. Here we report a “structural unit” analysis of [0011 tilt grain boundaries in YBa2Cu 3O7-δ (YBCO) that indicates there may be a simple structural origin for such localized donor states.

The Intrinsic Formation Of Localized Electronic States At [001] Tilt Grain Boundaries In YBa2Cu3O7 And Their Effect On Jc

1999 ◽  
Vol 5 (S2) ◽  
pp. 156-157
Author(s):  
J. P. Buban ◽  
N. D. Browning
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Plane ◽  
Localized States ◽  
Contrast Imaging ◽  
Structural Units ◽  
Band Bending ◽  
Tilt Boundaries ◽  
Donor States ◽  
P Type

Grain boundaries have long been known to have a deleterious effect on the superconducting critical current that can be carried by YBa2Cu3O7-δ. Recent theoretical analyses have proposed that the origin of this behavior may be band bending, which results in the depletion of charge carriers at the grain boundaries. For this to occur in these p-type superconductors there must, by definition, be a high density of localized donor states in the boundary plane. Here we describe a structural feature intrinsic to all [001] tilt boundaries that may be the origin of these localized states.Direct atomic-resolution images of asymmetric [001] tilt grain boundary structures have been obtained using the Z-contrast imaging technique. The grain boundaries are observed to be composed of distinct structural units, as shown in figure 1. Within these structural units, a 2×1 reconstruction of the CuO columns is seen to occur. This reconstruction, which is caused by the constraint imposed on the structure by the sizes of the component atoms, leads to effective oxygen vacancies in the grain boundary plane (figure 2). Further oxygen annealing of the boundary cannot fill these vacancies as there is no space in the structure for more oxygen atoms.

scholarly journals Molecular Doping in Multi-Molecule Polymer-Dopant Complexes Shows Reduced Coulomb Binding

2020 ◽  
Author(s):  
Chuanding Dong ◽  
Stefan Schumacher
Keyword(s):  
Charge Transfer ◽  
Organic Semiconductors ◽  
Positive Charge ◽  
Charge Carriers ◽  
Mechanistic Study ◽  
Charge Transfer Complexes ◽  
Mobile Charge ◽  
Molecular Doping ◽  
Gap States ◽  
P Type

<p>The mechanistic study of molecular doping of organic semiconductors (OSC) requires</p><p>an improved understanding of the role and formation of integer charge transfer complexes</p><p>(ICTC) on a microscopic level. In the present work we go one crucial step beyond</p><p>the simplest scenario of an isolated bi-molecular ICTC and study ICTCs formed of</p><p>up to two (poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b,3,4-b”]dithiophene)-alt-4,7-(2,1,3-</p><p>benzothiadiazole)](PCPDT-BT) oligomers and up to two CN6-CP molecules. We find that depending</p><p>on geometric arrangement, complexes containing two conjugated oligomers and two</p><p>dopant molecules can show p-type doping with double integer charge transfer, resulting in either</p><p>two singly doped oligomers or one doubly doped oligomer. Interestingly, compared to an individual</p><p>oligomer-dopant complex, the resulting in-gap states on the doped oligomers are significantly</p><p>lowered in energy. Indicating that, already in the relatively small systems studied here, Coulomb</p><p>binding of the doping-induced positive charge to the counter-ion is reduced which is an elemental</p><p>step towards generating mobile charge carriers through molecular doping.</p>

scholarly journals Molecular Doping in Multi-Molecule Polymer-Dopant Complexes Shows Reduced Coulomb Binding

2020 ◽  
Author(s):  
Chuanding Dong ◽  
Stefan Schumacher
Keyword(s):  
Charge Transfer ◽  
Organic Semiconductors ◽  
Positive Charge ◽  
Charge Carriers ◽  
Mechanistic Study ◽  
Charge Transfer Complexes ◽  
Mobile Charge ◽  
Molecular Doping ◽  
Gap States ◽  
P Type

<p>The mechanistic study of molecular doping of organic semiconductors (OSC) requires</p><p>an improved understanding of the role and formation of integer charge transfer complexes</p><p>(ICTC) on a microscopic level. In the present work we go one crucial step beyond</p><p>the simplest scenario of an isolated bi-molecular ICTC and study ICTCs formed of</p><p>up to two (poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b,3,4-b”]dithiophene)-alt-4,7-(2,1,3-</p><p>benzothiadiazole)](PCPDT-BT) oligomers and up to two CN6-CP molecules. We find that depending</p><p>on geometric arrangement, complexes containing two conjugated oligomers and two</p><p>dopant molecules can show p-type doping with double integer charge transfer, resulting in either</p><p>two singly doped oligomers or one doubly doped oligomer. Interestingly, compared to an individual</p><p>oligomer-dopant complex, the resulting in-gap states on the doped oligomers are significantly</p><p>lowered in energy. Indicating that, already in the relatively small systems studied here, Coulomb</p><p>binding of the doping-induced positive charge to the counter-ion is reduced which is an elemental</p><p>step towards generating mobile charge carriers through molecular doping.</p>

The structure of a near Σ=27 tilt grain boundary in Ge

1992 ◽  
Vol 50 (1) ◽  
pp. 214-215
Author(s):  
Stuart McKernan ◽  
C. Barry Carter
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Structural Unit ◽  
Perfect Crystal ◽  
Boundary Plane ◽  
Boundary Structure ◽  
Structural Units ◽  
Grain Boundary Plane ◽  
Grain Boundary Structure ◽  
Complex Structural

The modeling of tilt grain boundaries in terms of repeating structural units of varying separation is now a well established concept. High-resolution electron microscope (HREM) images of different tilt grain boundaries in many materials display a qualitative similarity of atomic configurations of the grain boundary structure. These boundaries are frequently described in terms of characteristic structural units, which may be separated from each other by regions of ‘perfect’ crystal (as, for example, in low-angle grain boundaries), or may be contiguous, forming ordered arrays of the structural units along the boundary. In general there will be a different arrangement of the structural units or an arrangement of different structural units, according to the precise geometry of the particular grain boundary. The structure of some special grain boundaries has been examined and these are found to exist in several different configurations, depending on the orientation of the grain boundary plane among other parameters. Symmetry-related symmetric tilt grain boundaries and asymmetric tilt grain boundaries with one grain having a prominent, low-index facet, are commonly observed, low-energy configurations. Structural multiplicity of these configurations along the same grain boundary has been observed in some systems. Defects in the perfect ordering of the structural units may be caused by deviations of the grain boundary plane away from the perfect tilt orientation. Deviations of grain boundary structure away from the exact orientation will also produce defects in the repeating structural unit configuration. These deviations may have a regular and well-defined structure, producing a more complex structural unit.

Photoemission Study of the Physical Nature of the InP Near-Surface Defect States

1986 ◽  
Vol 77 ◽  
Author(s):  
K. K. Chin ◽  
R. Cao ◽  
T. Kendelewicz ◽  
K. Miyano ◽  
J. J. Yeh ◽  
...  
Keyword(s):  
Surface Defect ◽  
Physical Nature ◽  
Defect States ◽  
Band Bending ◽  
Near Surface ◽  
Fermi Level Pinning ◽  
Low Temperature Annealing ◽  
Donor States ◽  
Photoemission Study ◽  
P Type

ABSTRACTThe physical nature of the InP near-surface defect acceptor and donor states are studied by using photoemission spectroscopy. It is found that the In/n-InP(110) interface band bending does not start until the In coverage reaches about 0.3 monolayer (ML), while the In/p-InP(110) band bending is almost saturated at 0.3 ML. The annealing effect on the band bending of clean cleaved n-and p-type InP(llO) surfaces is also studied. It is found that annealing of the clean surface creates an irreversible band bending effect on the p-InP(110), but the n-InP(110) almost does not show any band bending after low temperature annealing. Based on these two striking differences in the band bending behavior of n- and p-type InP, it is proposed that the physical nature of InP near-surface defect acceptor and donor levels may be different and that phosphorus vacancies are the cause of p-InP surface Fermi level pinning.

A Study of the Dependence of the Structure of Σ = 3 Tilt Boundaries in Gold on the Inclination of the Boundary Plane

1992 ◽  
Vol 278 ◽  
Author(s):  
Gui Jin Wang ◽  
V. Vitek
Keyword(s):  
Structural Unit ◽  
Atomic Level ◽  
Boundary Plane ◽  
Many Body ◽  
Chain Unit ◽  
Unit Model ◽  
Tilt Boundaries ◽  
A Chain ◽  
The Many ◽  
The Relationship

AbstractThe atomic structure of Σ = 3 tilt boundaries with variously inclined boundary planes has been studied using the many body potentials for gold. A chain unit model, analogous to the structural unit model, describes the relationship between different boundaries. The basic units in this model are units of the (111) and (112) twin boundaries and the model corresponds to atomic level faceting into these boundaries.

Defects in the Structure of Σ=27 Tilt Grain-Boundaries in Ge.

1990 ◽  
Vol 209 ◽  
Author(s):  
Stuart Mckernan ◽  
C. Barry Carter ◽  
Zvi Elgat
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Screw Dislocation ◽  
Structural Unit ◽  
Boundary Plane ◽  
High Angle ◽  
Structural Units ◽  
Short Segment ◽  
Tilt Boundaries ◽  
Tilt Grain Boundary

ABSTRACTGeneral high-angle tilt grain-boundaries may be described by an arrangement of repeating structural units. A particular defect in the normal arrangement of structural units in a Σ=27 <110> tilt grain-boundary in Ge is reported.The defect is characterized by a short segment of (111) facet at the interface, and is associated with a screw dislocation in the boundary plane. This defect accommodates a slight misorientation of the boundary away from the perfect tilt configuration, andmay represent a type of structural unit present in other tilt boundaries containing a small twist component.

Structure of grain boundaries: Correlation to supercurrent transport in textured Bi2Sr2Can−1CunOx bulk material

1997 ◽  
Vol 12 (11) ◽  
pp. 3009-3028 ◽  
Author(s):  
Y. Yan ◽  
M. A. Kirk ◽  
J. E. Evetts
Keyword(s):  
Grain Boundaries ◽  
Weak Link ◽  
Bulk Material ◽  
Boundary Plane ◽  
The Other ◽  
High Angle ◽  
Current Densities ◽  
Tilt Grain Boundary ◽  
P Type ◽  
Insight Into

Two kinds of characteristic grain boundaries were observed in textured Bi2Sr2Can−1CunOx (n = 2 and 3) bulk material: one (P-type) is nearly parallel to the (001) plane, and the other (N-type) is approximately normal to the (001) plane. Low-angle tilt N-type boundaries are composed of arrays of dislocations. However, for a small c-axis misorientation, the regions between the dislocation cores are still well connected, providing “pathways” for supercurrents crossing the boundary plane. The P-type boundaries exhibit compositionally and structurally modulated faceting. Although we see local regions of the low Tc (2201) phase at low-angle tilt (<10°) P-type boundaries, there are also “pathways” crossing the boundary plane made up of the high Tc (2212) and (2223) phases. The characteristics of such low-angle tilt grain boundary structures can therefore be modeled to provide general insight into the correlation between high critical current densities and low-texture breadths. On the other hand, a weak link could be formed at high-angle (> 10°) boundaries where there are the low Tc (2201) or insulating phases.

Diffraction effects from inclined grain boundaries in polycrystalline thin foils

1978 ◽  
Vol 36 (1) ◽  
pp. 420-421
Author(s):  
C.B. Carter ◽  
A.M. Donald ◽  
S.L. Sass
Keyword(s):  
Thin Film ◽  
Grain Boundaries ◽  
Boundary Plane ◽  
Foil Surface ◽  
Thin Foils ◽  
The Matrix ◽  
Firm Basis ◽  
Diffraction Patterns ◽  
Wave Matching ◽  
Diffraction Effects

Using thin-film gold bicrystals with the boundary plane parallel to the foil surface, it has been shown(l,2) that networks of grain boundary dislocations can act as diffraction gratings and give rise to subsidiary reflections close to the matrix reflections in electron diffraction patterns. Recently several groups of workers(3-5) have shown that inclined boundaries in polycrystalline specimens also produce extra reflections which may be due to the periodic nature of the boundaries. In general grain boundaries in polycrystalline specimens will be steeply inclined to the foil surface and additional reflections due to wave matching at the boundary(6) will also be present. The diffraction technique has the potential for providing detailed information on the structure of inclined boundaries (see, for example (5)), especially for the case where the image contains no useful information. In order to provide a firm basis for this technique, the geometry of the diffraction effects expected from inclined boundaries and the influence of these effects on the appearance of images will be examined.

Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p–n junction hybrids with electrodeposited Cu2O

Nanoscale ◽  
2014 ◽  
Vol 6 (15) ◽  
pp. 9148-9156 ◽  
Author(s):  
Joyashish Debgupta ◽  
Ramireddy Devarapalli ◽  
Shakeelur Rahman ◽  
Manjusha V. Shelke ◽  
Vijayamohanan K. Pillai
Keyword(s):  
Charge Carriers ◽  
Type Ii ◽  
Electrochemical Preparation ◽  
Enhanced Absorption ◽  
Absorption Of Light ◽  
Vertically Aligned ◽  
P Type

Heterojunction (type II) of self standing, vertically aligned CdSe NTs (n-type) with electrodeposited Cu2O (p-type) exhibits excellent photoresponse, resulting from enhanced absorption of light and faster transport of photogenerated charge carriers by CdSe NTs.

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