High-resolution X-ray diffraction and optical absorption study of heavily nitrogen-doped 4H–SiC crystals

AbstractHigh-resolution X-ray diffraction is one of the most powerful and widely used techniques for accurate characterization of the lattice parameters, mismatch, alloy composition, dopant concentrations, and thickness of epitaxial materials. In this presentation, we use a series of advanced X-ray diffraction techniques, including double-axis diffraction, triple-axis diffraction, reciprocal space mapping (RSM), and synchrotron white beam X-ray topography, to characterize highly nitrogen-doped homoepitaxial 4H-SiC epilayers. Measurements reported in this work have determined that in single crystal 4H-SiC, increasing the nitrogen doping level above 4 × 1017 cm#x2212;3 results in corresponding increase in lattice contraction. The increase in epilayer/mismatch mismatch with doping, and the corresponding strain energy, is attributed to the substitutional nitrogen incorporated preferentially in the host carbon sites of the 4H-SiC epilayer. Also, significant lattice tilts, generally along the [1120] offcut direction (8°), exist, which are believed to be induced by the Nagai epitaxial tilt.

Download Full-text

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055904 ◽

1982 ◽

Vol 40 ◽

pp. 722-723 ◽

Cited By ~ 1

Author(s):

R. Gronsky

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

High Resolution ◽

Computer Simulations ◽

Structural Characteristics ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Download Full-text

Tubulin structure at intermediate resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140634 ◽

1995 ◽

Vol 53 ◽

pp. 852-853

Author(s):

K. H. Downing ◽

S. G. Wolf ◽

E. Nogales

Keyword(s):

High Resolution ◽

Structural Data ◽

Therapeutic Drug ◽

Zinc Ions ◽

Two Dimensional ◽

X Ray Diffraction ◽

X Ray ◽

Negative Stain ◽

Functional Mechanisms ◽

Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

Download Full-text

High-resolution X-ray diffraction in crystalline structures with quantum dots

Uspekhi Fizicheskih Nauk ◽

10.3367/ufnr.0185.201505a.0449 ◽

2015 ◽

Vol 185 (5) ◽

pp. 449-478

Author(s):

Vasilii I. Punegov

Keyword(s):

Quantum Dots ◽

High Resolution ◽

X Ray Diffraction ◽

X Ray ◽

Crystalline Structures

Download Full-text

Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300004130 ◽

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.

Download Full-text

Energy Band Gap Studies of CdS Nanomaterials

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.3.97 ◽

2008 ◽

Vol 3 ◽

pp. 97-102 ◽

Cited By ~ 17

Author(s):

Dinu Patidar ◽

K.S. Rathore ◽

N.S. Saxena ◽

Kananbala Sharma ◽

T.P. Sharma

Keyword(s):

Optical Absorption ◽

Band Gap ◽

Energy Band ◽

Chemical Method ◽

Optical Absorption Spectroscopy ◽

Cds Nanoparticles ◽

X Ray Diffraction ◽

Energy Band Gap ◽

X Ray ◽

Simple Chemical

The CdS nanoparticles of different sizes are synthesized by a simple chemical method. Here, CdS nanoparticles are grown through the reaction of solution of different concentration of CdCl2 with H2S. X-ray diffraction pattern confirms nano nature of CdS and has been used to determine the size of particle. Optical absorption spectroscopy is used to measure the energy band gap of these nanomaterials by using Tauc relation. Energy band gap ranging between 3.12 eV to 2.47 eV have been obtained for the samples containing the nanoparticles in the range of 2.3 to 6.0 nm size. A correlation between the band gap and size of the nanoparticles is also established.

Download Full-text

Investigation of Residual Strains of the Second Kind in Plastically Deformed Metallic Materials

MRS Proceedings ◽

10.1557/proc-376-409 ◽

1994 ◽

Vol 376 ◽

Cited By ~ 2

Author(s):

M. Vrána ◽

P. Klimanek ◽

T. Kschidock ◽

P. Lukáš ◽

P. Mikula

Keyword(s):

High Resolution ◽

Neutron Diffraction ◽

Stacking Faults ◽

Metallic Materials ◽

Line Broadening ◽

X Ray Diffraction ◽

X Ray ◽

Neutron Diffractometer ◽

Residual Strains ◽

Good Agreement

ABSTRACTInvestigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.

Download Full-text