scholarly journals Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

2000 ◽  
Vol 5 (S1) ◽  
pp. 97-103
Author(s):  
Kathleen A. Dunn ◽  
Susan E. Babcock ◽  
Donald S. Stone ◽  
Richard J. Matyi ◽  
Ling Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
The Third ◽  
Dislocation Arrangement ◽  
Image Position ◽  
Gan Film

Diffraction-contrast TEM, focused probe electron diffraction, and high-resolution X-ray diffraction were used to characterize the dislocation arrangements in a 16µm thick coalesced GaN film grown by MOVPE LEO. As is commonly observed, the threading dislocations that are duplicated from the template above the window bend toward (0001). At the coalescence plane they bend back to lie along [0001] and thread to the surface. In addition, three other sets of dislocations were observed. The first set consists of a wall of parallel dislocations lying in the coalescence plane and nearly parallel to the substrate, with Burgers vector (b) in the (0001) plane. The second set is comprised of rectangular loops with b = 1/3 [110] (perpendicular to the coalescence boundary) which originate in the coalescence boundary and extend laterally into the film on the (100). The third set of dislocations threads laterally through the film along the [100] bar axis with 1/3<110>-type Burgers vectors These sets result in a dislocation density of ∼109 cm−2. High resolution X-ray reciprocal space maps indicate wing tilt of ∼0.5º.

Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

1999 ◽  
Vol 595 ◽  
Author(s):  
Kathleen A. Dunn ◽  
Susan E. Babcock ◽  
Donald S. Stone ◽  
Richard J. Matyi ◽  
Ling Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Dislocation Density ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
The Third ◽  
Dislocation Arrangement ◽  
Gan Film

AbstractDiffraction-contrast TEM, focused probe electron diffraction, and high-resolution X-ray diffraction were used to characterize the dislocation arrangements in a 16[.proportional]m thick coalesced GaN film grown by MOVPE LEO. As is commonly observed, the threading dislocations that are duplicated from the template above the window bend toward (0001). At the coalescence plane they bend back to lie along [0001] and thread to the surface. In addition, three other sets of dislocations were observed. The first set consists of a wall of parallel dislocations lying in the coalescence plane and nearly parallel to the substrate, with Burgers vector (b) in the (0001) plane. The second set is comprised of rectangular loops with b = 1/3 [11 20] (perpendicular to the coalescence boundary) which originate in the coalescence boundary and extend laterally into the film on the (1 100). The third set of dislocations threads laterally through the film along the [1 100] bar axis with 1/3<11 20>-type Burgers vectors These sets result in a dislocation density of ∼109 cm−2. High resolution X-ray reciprocal space maps indicate wing tilt of ∼0.5°.

Effects of Phosphorus Exposure on Arsenic-Stabilized GaAs 2×4 Surface

1993 ◽  
Vol 312 ◽  
Author(s):  
A. H. Bensaoula ◽  
A. Freundlich ◽  
A. Bensaoula ◽  
V. Rossignol
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Growth Process ◽  
High Energy ◽  
Ex Situ ◽  
Chemical Beam Epitaxy ◽  
High Energy Electron ◽  
X Ray Diffraction ◽  
X Ray

AbstractPhosphorus exposed GaAs (100) surfaces during a Chemical Beam Epitaxy growth process are studied using in-situ Reflection High Energy Electron Diffraction and ex-situ High Resolution X-ray Diffraction. It is shown that the phosphorus exposure of a GaAs (100) surface in the 500 – 580 °C temperature range results in the formation of one GaP monolayer.

Study of Different Dislocations in YBCO Thin Film

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3530-3533
Author(s):  
S. X. Wang ◽  
W. L. Liu ◽  
S. H. Han ◽  
H. Zhang
Keyword(s):  
Thin Film ◽  
High Resolution ◽  
Screw Dislocation ◽  
Threading Dislocations ◽  
Thin Film Sample ◽  
Ybco Thin Film ◽  
Film Sample ◽  
X Ray Diffraction ◽  
X Ray ◽  
Out Of Plane

A series thin film sample of YBCO with different value of Tc was studied by high-resolution X-ray diffraction. Two different threading dislocations, the in-plane twist and the out-of-plane tilt, were studied carefully. It is found that the value of Tc is much more sensitive to the substrate normal tilt than to the in-plane twist. Dislocations with different Burgers vectors are suggested to exert different influence on the value of Tc of the YBCO thin film. The screw dislocation in the film is strongly influences the properties of the YBCO.

Determination of the Twist Angle of GaN Film by High Resolution X-ray Diffraction

2008 ◽  
Vol 1 ◽  
pp. 045004 ◽  
Author(s):  
Hongtao Li ◽  
Yi Luo ◽  
Lai Wang ◽  
Guangyi Xi ◽  
Yang Jiang ◽  
...  
Keyword(s):  
High Resolution ◽  
Twist Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gan Film

scholarly journals MicroED: a versatile cryoEM method for structure determination

2018 ◽  
Vol 2 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Brent L. Nannenga ◽  
Tamir Gonen
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Electron Diffraction ◽  
Structure Determination ◽  
Materials Science ◽  
Electron Diffraction Data ◽  
Determination Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

Micro-electron diffraction, or MicroED, is a structure determination method that uses a cryo-transmission electron microscope to collect electron diffraction data from nanocrystals. This technique has been successfully used to determine the high-resolution structures of many targets from crystals orders of magnitude smaller than what is needed for X-ray diffraction experiments. In this review, we will describe the MicroED method and recent structures that have been determined. Additionally, applications of electron diffraction to the fields of small molecule crystallography and materials science will be discussed.

Structure determination of a new polymorph of TiO2 by high-resolution electron microscopy and computer simulations

1989 ◽  
Vol 47 ◽  
pp. 416-417
Author(s):  
Jillian F. Banfield ◽  
David R. Veblen ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Computer Simulations ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Resolution Electron

A new, naturally occurring polymorph of TiO2 has been identified. This mineral forms lamellae generally only a few nanometers wide in anatase from two localities near Bintal Valais, Switzerland. The abundance of this mineral in anatase is too low to allow investigation by X-ray diffraction. The unit cell determined by electron diffraction is triclinic, with a = 0.754 nm, b = 0.448 nm, c = 0.616 nm, α = 78.90°, β = 124.55°, γ = 96.54°. The coherently intergrown lamellae are oriented with b parallel to a of anatase; the interface is parallel to (103) anatase.

Complex Superstructures Resulting from Compositional Modulation and Octahedral Tilt Twinning in AA′BB′O6 Doubly Cation Ordered Perovskites

2013 ◽  
Vol 2013 (CICMT) ◽  
pp. 000006-000013
Author(s):  
Graham King ◽  
Susana Garcia-Martin ◽  
Esteban Urones-Garrote ◽  
Gwilherm Nenert ◽  
Patrick M. Woodward
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compositional Modulation ◽  
System A ◽  
Transmission Electron

The ordering of cations within the perovskite structure can have a profound effect on the physical properties. A number of AA′BB′O6 perovskite phases which have both a rock salt ordering of the B/B′ cations and a layered ordering of the A/A′ cations have recently been prepared and studied. In some of these compositions complex nanoscale superstructure formation has been observed. These superstructures are the result of compositional modulations involving the occupancies of the A and A′ cations and are accompanied by a twinning of the octahedral tilt system. A wide variety of patterns are observed, such as 1-dimensional stripes or 2-dimensional chessboards which can have periodicities which are either commensurate or incommensurate with the underlying subcell. These superstructures cannot be easily detected by powder X-ray diffraction but have been observed using a combination of high resolution transmission electron microscopy, electron diffraction, and neutron powder diffraction. The factors which determine the dimensionality and periodicity of the superstructures are discussed and compared with the closely related Li based perovskite systems.

scholarly journals Structure of the quaternary alloy Zn0.6Mn0.4In2S4from synchrotron powder diffraction and electron transmission microscopy

2006 ◽  
Vol 39 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Rosario Ávila-Godoy ◽  
Asiloé J. Mora ◽  
Dwight R. Acosta-Najarro ◽  
Gerzon E. Delgado ◽  
Santos A. López-Rivera ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Parent Compound ◽  
Quaternary Alloy ◽  
X Ray Diffraction ◽  
Transmission Microscopy ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Synchrotron Powder Diffraction

The aim of the present work was to determine the structure of the quaternary alloy Zn0.6Mn0.4In2S4and to locate the Mn2+. This was accomplished by means of powder synchrotron X-ray diffraction, high-resolution microscopy and convergent-beam electron diffraction (CBED). The powder X-ray diffraction pattern was indexed in a rhombohedral cell, with cell constantsa= 3.875 (2),c= 37.208 (4) Å, and possible space groupsR\bar{3}morR3m. Rietveld refinements using different cationic arrangements in these space groups were performed. A model in space groupR3m, in which the tetrahedral and octahedral sites were occupied by different proportions of Zn, Mn and In atoms, gave the best result. The Rietveld refinement of this model led to figures of meritRwp= 9.8%,Rp= 9.1% and χ2= 11.1. Selected-area electron diffraction patterns and high-resolution transmission electron micrographs along [001] reveal the rhombohedral configuration. CBED patterns perpendicular to [001], showing the distinctive 3msymmetry, confirmed space groupR3mand the breaking of the centrosymmetry of the parent compound, ZnIn2S4.

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