TEM Observation of the Polytype Transformation of Bulk SiC Ingot

2008 ◽  
Vol 600-603 ◽  
pp. 365-368 ◽  
Author(s):  
Masahiko Aoki ◽  
Megumi Miyazaki ◽  
Taro Nishiguchi ◽  
Hiroyuki Kinoshita ◽  
Masahiro Yoshimoto
Keyword(s):  
Raman Spectroscopy ◽  
Diffraction Pattern ◽  
Growth Direction ◽  
Selected Area Diffraction Pattern ◽  
Polytype Transformation

This article describes the analysis of the polytype transformation of SiC ingot. We analyzed the sample by Raman spectroscopy and TEM observation. The result of the analysis shows the polytype is transformed from 4H-SiC to 6H-SiC, and then returned to 4H-SiC. We found that the direction of the c-axis is not the same as the growth direction of the ingot. And also we found the existence of 8H-SiC at the interface between 6H-SiC and 4H-SiC region by the selected area diffraction pattern and confirmed it by HR-TEM observation.

Using the TEM Condenser Lens to Switch between Image and Diffraction Modes

2013 ◽  
Vol 21 (2) ◽  
pp. 40-40
Author(s):  
Lydia Rivaud
Keyword(s):  
Electron Microscope ◽  
Diffraction Pattern ◽  
Transmission Electron Microscope ◽  
Condenser Lens ◽  
Selected Area Diffraction Pattern ◽  
Transmission Electron ◽  
Set Up ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Central to the operation of the transmission electron microscope (TEM) (when used with crystalline samples) is the ability to go back and forth between an image and a diffraction pattern. Although it is quite simple to go from the image to a convergent-beam diffraction pattern or from an image to a selected-area diffraction pattern (and back), I have found it useful to be able to go between image and diffraction pattern even more quickly. In the method described, once the microscope is set up, it is possible to go from image to diffraction pattern and back by turning just one knob. This makes many operations on the microscope much more convenient. It should be made clear that, in this method, neither the image nor the diffraction pattern is “ideal” (details below), but both are good enough for many necessary procedures.

Growth direction determination of a single RuO2 nanowire by polarized Raman spectroscopy

2010 ◽  
Vol 96 (21) ◽  
pp. 213108 ◽  
Author(s):  
Myung Hwa Kim ◽  
Jeong Min Baik ◽  
Seung Joon Lee ◽  
Hae-Young Shin ◽  
Jaeyeon Lee ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Growth Direction ◽  
Polarized Raman Spectroscopy ◽  
Polarized Raman

scholarly journals Nanocrystal assembly for bottom-up plasmonic materials and surface-enhanced Raman spectroscopy (SERS) sensing

2009 ◽  
Vol 81 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Andrea R. Tao
Keyword(s):  
Raman Spectroscopy ◽  
Building Blocks ◽  
Surface Enhanced Raman Spectroscopy ◽  
Growth Direction ◽  
Support Surface ◽  
Bottom Up ◽  
Plasmonic Materials ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Visible Wavelengths

Plasmonic materials are emerging as key platforms for applications that rely on the manipulation of light at small length scales. Sub-wavelength metallic features support surface plasmons that can induce huge local electromagnetic fields at the metal surface, facilitating a host of extraordinary optical phenomena. Ag nanocrystals (NCs) and nanowires (NWs) are ideal building blocks for the bottom-up fabrication of plasmonic materials for photonics, spectroscopy, and chemical sensing. Faceted Ag nanostructures are synthesized using a colloidal approach to regulate nucleation and crystallographic growth direction. Next, new methods of nanoscale organization using Langmuir-Blodgett (LB) compression are presented where one- and two-dimensional assemblies can be constructed with impressive alignment over large areas. Using this method, plasmon coupling between Ag nanostructures can be controlled by varying spacing and density, achieving for the first time a completely tunable plasmon response in the visible wavelengths. Lastly, these assemblies are demonstrated as exceptional substrates for surface-enhanced Raman spectroscopy (SERS) by achieving high chemical sensitivity and specificity, exhibiting their utility as portable field sensors, and integrating them into multiplexed "lab-on-a-chip" devices.

New phases in the Al-Co-Cu alloy system : Marked variations from the “true” decagonal phase

1992 ◽  
Vol 50 (1) ◽  
pp. 32-33
Author(s):  
Atul S. Ramani ◽  
Lucille A. Giannuzzi ◽  
Altaf H. Carim ◽  
William R. Bitler ◽  
Paul R. Howell
Keyword(s):  
Single Crystal ◽  
Diffraction Pattern ◽  
Alloy System ◽  
Fivefold Symmetry ◽  
Decagonal Phase ◽  
Cu Alloy ◽  
Selected Area Diffraction Pattern ◽  
The One ◽  
Pentagonal Symmetry ◽  
Incommensurate Phases

The decagonal phase in the Al-Co-Cu alloy system was first discovered by He et al. We shall call this phase the “true” decagonal phase (TD) phase because it is the one most commonly observed in the Al-Co-Cu alloy system. It is well known that quasicrystalline phases such as the TD phase contain the phason defect peculiar to incommensurate phases that causes subtle variations from perfect decagonal symmetry. In this paper we report on the existence of new phases in the Al-Co-Cu alloy system, that are related to the TD phase but yet show marked variations from the TD phase. These variations are too drastic to be caused by phason defects alone.Figure 1(a) is a selected area diffraction pattern (SADP) recorded from a TD phase single “crystal” showing near perfect decagonal (tenfold) symmetry. This SADP agrees very well with the first published SADP of the TD phase in Al-Co-Cu that also shows almost perfect decagonal symmetry. In a previous paper we have reported several kinds of deviations from perfect decagonal symmetry, but none of these deviations involved the observation of perfect pentagonal (fivefold) symmetry. Figure 1(b) is an SADP recorded from a phase in Al-Co-Cu that exhibits perfect pentagonal symmetry instead of the expected decagonal symmetry. This breakdown of true tenfold symmetry into true fivefold symmetry is caused by unequal intensities of equal and opposite reflections. This example is a clear violation of Friedel's law, which states that the intensities of equal and opposite diffraction vectors must be equal.

Analysis of electron-diffraction intensity profiles using a photodiode-array detection system

1983 ◽  
Vol 41 ◽  
pp. 322-323
Author(s):  
J. B. Warren
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Detection System ◽  
High Energy ◽  
Photographic Emulsion ◽  
Diffraction Intensity ◽  
Silicon Photodiode ◽  
Photodiode Array Detection ◽  
Analog To Digital ◽  
Photodiode Array

Electron diffraction intensity profiles have been used extensively in studies of polycrystalline and amorphous thin films. In previous work, diffraction intensity profiles were quantitized either by mechanically scanning the photographic emulsion with a densitometer or by using deflection coils to scan the diffraction pattern over a stationary detector. Such methods tend to be slow, and the intensities must still be converted from analog to digital form for quantitative analysis. The Instrumentation Division at Brookhaven has designed and constructed a electron diffractometer, based on a silicon photodiode array, that overcomes these disadvantages. The instrument is compact (Fig. 1), can be used with any unmodified electron microscope, and acquires the data in a form immediately accessible by microcomputer.Major components include a RETICON 1024 element photodiode array for the de tector, an Analog Devices MAS-1202 analog digital converter and a Digital Equipment LSI 11/2 microcomputer. The photodiode array cannot detect high energy electrons without damage so an f/1.4 lens is used to focus the phosphor screen image of the diffraction pattern on to the photodiode array.

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