Growth of Boron Carbide Crystals from a Copper Flux

2009 ◽  
Vol 1164 ◽  
Author(s):  
Yi Zhang ◽  
James Edgar ◽  
Jack Plummer ◽  
Clinton Whiteley ◽  
Hui Chen ◽  
...  
Keyword(s):  
Boron Carbide ◽  
Potassium Hydroxide ◽  
Crystal Size ◽  
Optical Microscope ◽  
Etch Pit Density ◽  
Bulk Crystals ◽  
Limited Growth ◽  
Etch Pits ◽  
X Ray ◽  
Etch Pit

AbstractBoron carbide crystals ranging in size from 50 microns to several millimeters have been grown from a copper-boron carbide flux at temperatures from 1500°C to 1750°C. The crystal size increased with growth temperature although copper evaporation limited growth at the higher temperatures. Synchrotron X-ray Laue patterns were indexed according to (001) orientation boron carbide structure, indicating the bulk crystals were single crystalline with {001} growth facets. Raman spectrum of boron carbide indicates an improved crystal quality compared to the source powder, but peaks of crystals grown from 11B -enriched source shifted to the lower energy by 1-4 cm−1 from literature values, possibly due to the boron isotope dependency. Five fold symmetry defects and twin planes were common as observed by optical microscope and scanning electron microscope. Raindrop shape etch pits were formed after defect selective etching in molten potassium hydroxide at 600°C for 6 minutes. Typically, the etch pit density was on the order of 106/cm2.

Defect-Selective Etching of Icosahedral Boron Arsenide (B12As2) Crystals in Molten Potassium Hydroxide

2011 ◽  
Vol 1307 ◽  
Author(s):  
C.E. Whiteley ◽  
A. Mayo ◽  
J.H. Edgar ◽  
M. Dudley ◽  
Y. Zhang
Keyword(s):  
Potassium Hydroxide ◽  
High Energy ◽  
Selective Etching ◽  
Etch Pits ◽  
X Ray ◽  
Etch Pit ◽  
Dislocation Densities ◽  
Boron Arsenide ◽  
Defect Densities ◽  
Molten Nickel

ABSTRACTThe present work reports on the defect-selective etching (DSE) for estimating dislocation densities in icosahedral boron arsenide (B12As2) crystals using molten potassium hydroxide (KOH). DSE takes advantage of the greater reactivity of high-energy sites surrounding a dislocation, compared to the surrounding dislocation-free regions. The etch pits per area are indicative of the defect densities in the crystals, as confirmed by x-ray topography (XRT). Etch pit densities were determined for icosahedral boron arsenide crystals produced from a molten nickel flux as a function of etch time (1-5 minutes) and temperature (400-700°C). The etch pits were predominately triangle shaped, and ranged in size from 5-25μm. The average etch pit density of the triangle and oval etch-pits was on the order of 5x107cm-2 and 3x106cm-2 (respectively), for crystals that were etched for two minutes at 550°C.

Characterization and Mapping of Crystal Defects in Silicon Carbide

2004 ◽  
Vol 815 ◽  
Author(s):  
E. Emorhokpor ◽  
T. Kerr ◽  
I. Zwieback ◽  
W. Elkington ◽  
M. Dudley ◽  
...  
Keyword(s):  
Image Processing ◽  
Silicon Carbide ◽  
Potassium Hydroxide ◽  
Crystal Defects ◽  
Etch Pits ◽  
Accurate Analysis ◽  
Etching Technique ◽  
X Ray ◽  
Etch Pit ◽  
Density Maps

AbstractA method is presented for detecting, counting and mapping micropipes and dislocations in n+, undoped, and semi-insulating Silicon Carbide wafers. The technique is based on etching in molten Potassium Hydroxide (KOH), and it employs image processing that automatically detects etch pits, discriminates between micropipes and dislocations, and generate micropipe and dislocation density maps. We demonstrate a novel way of detecting and mapping dislocations and micropipes in semi-insulating SiC. This is achieved by combining a properly tuned etching technique that reliably produces well defined etch pits with image processing that enables quick and accurate analysis of the etch pit contrast. We show that the results of optical evaluation are close to those obtained using the Synchrotron White Beam X-Ray Topography (SWBXT) technique.

Mosaicity and Wafer Bending in SiC Wafers as Measured by Double and Triple Crystal X-Ray Rocking Curve and Peak Position Maps

2007 ◽  
Vol 556-557 ◽  
pp. 213-218 ◽  
Author(s):  
K.W. Kirchner ◽  
Kenneth A. Jones ◽  
Michael A. Derenge ◽  
Michael Dudley ◽  
Adrian R. Powell
Keyword(s):  
Laser Light ◽  
Peak Position ◽  
Etch Pit Density ◽  
Normal Position ◽  
Rocking Curve ◽  
X Ray ◽  
Etch Pit ◽  
Density Map ◽  
Beam Transmission ◽  
Si Wafer

Double and triple crystal rocking curve and peak position maps are constructed for a 4HSiC wafer for the symmetric (0 0 0 8) reflection in the normal position, the same reflection for a sample rotated 90º, and an asymmetric (1 23 6) reflection for the wafer in the normal position. These measurements were corrected for the ‘wobble’ in the instrument by scanning a 4” (1 1 1) Si wafer and assuming that the Si wafer was perfect and attributing the variations in the measurements to instrumental error. The x-ray measurements are correlated with a cross polar image, etch pit density map, white beam transmission x-ray topograph, and a laser light scan.

Density and Behavior of Etch Pits on C-Face 4H-SiC Surface Produced by CIF3 Gas

2012 ◽  
Vol 717-720 ◽  
pp. 379-382 ◽  
Author(s):  
Hitoshi Habuka ◽  
Kazuchika Furukawa ◽  
Toshimitsu Kanai ◽  
Tomohisa Kato
Keyword(s):  
Substrate Temperature ◽  
Crystal Quality ◽  
Etch Pit Density ◽  
Etch Pits ◽  
Etch Pit ◽  
And Behavior

The etch pit density produced on the C-face 4H-SiC substrate using chlorine trifluoride gas at various temperatures was evaluated. Because the etch pit density formed at the substrate temperature of 713 K showed the comparable value to the current dislocation level of the Si-face 4H-SiC, the etch pit density obtained by this technique is considered to have a relationship with the crystal quality.

SCANNING NEAR-FIELD OPTICAL MICROSPECTROSCOPY OF SINGLE PERYLENE MICROCRYSTALS

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3901-3903 ◽  
Author(s):  
JUN-ICHI NIITSUMA ◽  
TORU FUJIMURA ◽  
TADASHI ITOH ◽  
HITOSHI KASAI ◽  
SHUJI OKADA ◽  
...  
Keyword(s):  
Fluorescence Spectra ◽  
Crystal Size ◽  
Size Dependence ◽  
Near Field ◽  
Optical Microscope ◽  
Characteristic Change ◽  
Bulk Crystals ◽  
Critical Difference ◽  
Modified Technique ◽  
Environmental Difference

Perylene microcrystals are known to show characteristic change in the exciton fluorescence spectra depending on the crystal size less than about 200nm. However, the origin of the size-dependence is not yet clear. In this work, we have studied on individual microcrystals by a scanning near-field optical microscope (SNOM). The samples were prepared by a modified technique based on reprecipitation method. As a result, we could successfully measure the topographic and fluorescence images of perylene microcrystals with the size of ~200nm by SNOM at room temperature. In the fluorescence spectra of the single microcrystals, free and self-trapped exciton bands were successfully observed but they did not show any critical difference from that of the bulk crystals. Some possibility of environmental difference is discussed.

X-Ray, Photoluminescence and Etching Studies of Indium-Doped LPE GaAs Layers

1988 ◽  
Vol 144 ◽  
Author(s):  
J.F. Chen ◽  
C. R. Wie ◽  
F. A. Junga
Keyword(s):  
Phase Diagram ◽  
Sharp Increase ◽  
Emission Spectra ◽  
Etch Pit Density ◽  
Double Crystal ◽  
X Ray ◽  
Etch Pit ◽  
In Doping ◽  
Good Crystalline Quality ◽  
Pseudobinary Phase Diagram

ABSTRACTThe effects of In doping on the structural properties of liquid phase epitaxially (LPE) grown GaAs layers are studied. The distribution coefficient of In in the GaAs at 800 ° C was determined to be 0.033 which was consistent with the value calculated from the pseudobinary phase diagram of the ternary system at a dilute In concentration. The full widths at halfmaximum (FWHM) of x-ray double crystal rocking curves show that a GaAs epi-layer of good crystalline quality can be obtained by doping In to a concentration up to 4.3 × 1019 cm−3, beyond which a sharp increase in the FWHM is observed. Etch pit density (EPD) measurement shows that the dislocation density is reduced by doping the epi-layer with In. At the optimal In concentration of 2.4 × 1019 cm−3, the EPD is reduced by a factor of 20 when measured at the surface of a 9 um thick epilayer.Photoluminesce measurements made at 15 K show two sharp emission spectra near the bandedge. The relative intensities of the two emissions, I(l.49eV)/I(l.5eV) are reduced with increasing In content. This suggests that incorporation of Carbon acceptors is suppressed by In doping in the GaAs epilayers. The FWHM as small as 5 meV of the bandedge transition was obtained for the epi-layer doped with In concentration of 2.4 × 1019 cm−3.

Microstructural Transformation of Titanium-Boron Carbide (B4C) Powder Mixture during Spark Plasma Sintering

2015 ◽  
Vol 764-765 ◽  
pp. 51-55
Author(s):  
V.S. Balaji ◽  
S. Kumaran
Keyword(s):  
Boron Carbide ◽  
Microstructural Evolution ◽  
Powder Mixture ◽  
Optical Microscope ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Energy Dispersive Spectroscope

Present study investigates the microstructural evolution and in-situ formation of Ti/(TiB+TiC) composite. The sintered compacts are having near theoretical density. The relative density of Ti/(TiB+TiC) composites decreases with increasing TiB and TiC content.The phase evolutions of TiB and TiC according to the in-situ reactions are analyzed by X-Ray diffraction technique (XRD). Optical microscope (OM) and Energy dispersive spectroscope (EDS) observations of the Ti/(TiB+TiC) composites shows the presence of TiC and TiB reinforcements as equiaxed and needle like structures respectively.

Growth and Structural Characterization of Znse Single Crystals

1989 ◽  
Vol 152 ◽  
Author(s):  
Elmer E. Anderson ◽  
Hai- Yuin Cheng ◽  
Michael J. Edgell
Keyword(s):  
Single Crystals ◽  
Electron Spectroscopy ◽  
Vapor Transport ◽  
X Ray Diffraction ◽  
Etch Pits ◽  
X Ray ◽  
Etch Pit ◽  
Auger Microscopy ◽  
Transport Method

ABSTRACTSingle crystals of ZnSe have been grown by the physical vapor transport method in sealed quartz ampoules. The largest crystal grown measures 1 cm x 4 mm x 2 mm and required a total growing time of 11 days. Polished wafers cut from the crystals have been etched and examined by optical microscopy, x-ray diffraction, scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and scanning Auger microscopy (SAM). No impurities or unwanted phases were detected, but frequent twinning occurs. Zn-rich {111} faces were identified by SAM. Triangular etch pits are observed on Zn {lll} faces but not on Se faces. Etch pit densities are about 104 per cm2 on slow-cooled samples but are about 100 times greater when cooling is more rapid.

Elementary Screw and Mixed-Type Dislocations in 4H-SiC Characterized by X-Ray Topography Taken with Six Equivalent 11-28 g-Vectors and a Comparison to Etch Pit Evaluation

2017 ◽  
Vol 897 ◽  
pp. 185-188 ◽  
Author(s):  
Yong Zhao Yao ◽  
Yukari Ishikawa ◽  
Yoshihiro Sugawara ◽  
Yumiko Takahashi ◽  
Keiichi Hirano
Keyword(s):  
Chemical Etching ◽  
Mixed Type ◽  
Threading Dislocations ◽  
Etch Pits ◽  
X Ray ◽  
Etch Pit

We have studied threading dislocations (TDs) in 4H-SiC by means of X-ray topography (XRT) taken under 6 equivalent g-vector of 11-28 and two different chemical etching methods. Threading screw and mixed-type dislocations (TSDs and TMDs) can be distinguished and the direction of the a-components of TMDs can be determined by XRT. Efforts have been made to examine if there are features of etch pits that can be used to distinguish TMDs from TSDs.

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