Influence of Micropipe and Domain Boundary in SiC Substrate on the DC Characteristics of AlGaN/GaN HFET

2007 ◽  
Vol 556-557 ◽  
pp. 1043-1046 ◽  
Author(s):  
Hiroyuki Sazawa ◽  
Tomohisa Kato ◽  
Kazutoshi Kojima ◽  
K. Furuta ◽  
K. Hirata ◽  
...  
Keyword(s):  
Domain Boundary ◽  
Topographic Analysis ◽  
Raman Analysis ◽  
X Ray ◽  
Free Carriers ◽  
Crystal Imperfections ◽  
Dc Characteristics ◽  
Domain Boundaries ◽  
Gan Hfet ◽  
Gan Crystal

AlGaN/GaN HFETs were fabricated around micropipes and on a domain boundary in a semi-insulating silicon carbide (SI-SiC) substrate and the DC characteristics of the fabricated devices were measured. Devices around micropipe showed no pinch-off or large gate leakage. The devices on the domain boundaries showed no degradation in the performances, even though an X-ray topographic analysis indicated that crystal imperfections, due to the defects, propagated to the GaN layer across the hetero interface. Based on these results, we concluded that micropipe degrades the DC characteristics and that the domain boundary does not affect the DC characteristics. From Raman analysis on the devices around the micropipes, these degradations could be attributed to the free carriers introduced into the GaN crystal by the micropipes.

Influence of Micropipe and Domain Boundary in SiC Substrate on the DC Characteristics of AlGaN/GaN HFET

2007 ◽  
pp. 1043-1046
Author(s):  
Hiroyuki Sazawa ◽  
Tomohisa Kato ◽  
Kazutoshi Kojima ◽  
K. Furuta ◽  
K. Hirata ◽  
...  
Keyword(s):  
Domain Boundary ◽  
Dc Characteristics ◽  
Gan Hfet

Antiphase Boundaries in Ordered Ni3FE Crystals

1969 ◽  
Vol 27 ◽  
pp. 62-63
Author(s):  
Y. H. Liu
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardening Mechanism ◽  
Superlattice Structure ◽  
Disordered Phase ◽  
Domain Boundaries ◽  
Atomic Scattering ◽  
The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

scholarly journals Activated Charcoal Supported Cadmium Doped TiO2 for Photocatalytic and Antibacterial Applications

2015 ◽  
Vol 44 ◽  
pp. 108-123 ◽  
Author(s):  
S. Prabha ◽  
V.L. Chandraboss ◽  
J. Kamalakannan ◽  
S. Senthilvelan
Keyword(s):  
Uv Light ◽  
Precipitation Method ◽  
Scanning Electron Micrographs ◽  
X Ray Diffraction ◽  
Raman Analysis ◽  
X Ray ◽  
Photo Catalytic Activity ◽  
Photocatalytic Effect ◽  
Fourier Transform Raman ◽  
Ft Raman

The photocatalytic activity was studied under UV light using AC-Cd/TiO2 prepared via precipitation method and characterized by powder X-ray diffraction (XRD) , high resolution scanning electron micrographs (HR-SEM) with energy dispersive X-ray analysis (EDX), photoluminescence (PL) and Fourier transform Raman analysis (FT-RAMAN). The enhanced photo catalytic activity of the AC-Cd/TiO2 is demonstrated through photodegradation of methylene blue under UV light radiation at 365 nm. The mechanism of photocatalytic effect of AC-Cd/TiO2 nanocomposite material has been discussed Further its antibacterial activity against two gram positive and two gram negative bacterial strain is studied.

On Low Voltage Scanning Electron Microscopy and Chemical Microanalysis

2000 ◽  
Vol 6 (4) ◽  
pp. 307-316 ◽  
Author(s):  
E.D. Boyes
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Spatial Resolution ◽  
Low Voltage ◽  
Energy Dispersive ◽  
Beam Specimen ◽  
Topographic Analysis ◽  
X Ray ◽  
Voltage Scanning ◽  
Scanning Electron

AbstractThe current status and general applicability of scanning electron microscopy (SEM) at low voltages is reviewed for both imaging (low voltage scanning electron microscopy, LVSEM) and chemical microanalysis (low voltage energy-dispersive X-ray spectrometry, LVEDX). With improved instrument performance low beam energies continue to have the expected advantages for the secondary electron imaging of low atomic number (Z) and electrically non-conducting samples. They also provide general improvements in the veracity of surface topographic analysis with conducting samples of all Z and at both low and high magnifications. In new experiments the backscattered electron (BSE) signal retains monotonic Z dependence to low voltages (<1 kV). This is contrary to long standing results in the prior literature and opens up fast chemical mapping with low dose and very high (nm-scale) spatial resolution. Similarly, energy-dispersive X-ray chemical microanalysis of bulk samples is extended to submicron, and in some cases to <0.1 μm, spatial resolution in three dimensions at voltages <5 kV. In favorable cases, such as the analysis of carbon overlayers at 1.5 kV, the thickness sensitivity for surface layers is extended to <2 nm, but the integrity of the sample surface is then of concern. At low beam energies (E0) the penetration range into the sample, and hence the X-ray escape path length out of it, is systematically restricted (R = F(E05/3)), with advantages for the accuracy or elimination of complex analysis-by-analysis matrix corrections for absorption (A) and fluorescence (F). The Z terms become more sensitive to E0 but they require only one-time calibrations for each element. The new approach is to make the physics of the beam–specimen interactions the primary factor and to design enabling instrumentation accordingly.

Structural and ferromagnetic properties of Cu-doped GaN

2007 ◽  
Vol 22 (5) ◽  
pp. 1396-1405 ◽  
Author(s):  
B. Seipel ◽  
R. Erni ◽  
Amita Gupta ◽  
C. Li ◽  
F.J. Owens ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Electron Gun ◽  
Superconducting Quantum Interference Device ◽  
X Ray Diffraction ◽  
Calcination Process ◽  
X Ray ◽  
Lattice Constants ◽  
Gan Crystal ◽  
Electron Energy Loss ◽  
Atomic And Electronic Structure

The wurtzite polymorph of GaN was calcined with CuO in flowing nitrogen. As a result of this processing, both superconducting quantum interference device magnetometry and ferromagnetic resonance studies showed ferromagnetism in these samples at room temperature. These magnetic results are qualitatively consistent with very recent first-principle calculations [Wu et al., Appl. Phys. Lett.89, 062505 (2006)] that predict ferromagnetism in Cu-doped GaN. We focus in this paper on analyzing changes in the GaN atomic and electronic structure due to calcination with CuO using multiple analytical methods. Quantitative powder x-ray diffraction (XRD) showed changes in the lattice constants of the GaN due to the incorporation of copper (and possibly oxygen). Energy-dispersive x-ray spectroscopy proved the incorporation of copper into the GaN crystal structure. Electron-gun monochromated electron energy loss spectroscopy showed CuO calcinations-induced GaN band gap changes and indicated changes in the atomic arrangements due to the calcination process. The fine structure of the N K-edge showed differences in the peak ratios with respect to higher nominal CuO contents, corresponding to an increase in the c-lattice constant as confirmed by XRD.

X-Ray Topographic Observation of Antiferromagnetic Domain Boundaries in Chromium

1971 ◽  
Vol 26 (6) ◽  
pp. 321-323 ◽  
Author(s):  
Sukeaki Hosoya ◽  
Masami Ando
Keyword(s):  
X Ray ◽  
Domain Boundaries

scholarly journals Matching X-ray beam and detector properties to protein crystals of different perfection

2014 ◽  
Vol 21 (3) ◽  
pp. 537-546 ◽  
Author(s):  
Colin Nave
Keyword(s):  
Data Processing ◽  
Room Temperature ◽  
Angular Resolution ◽  
Block Size ◽  
Quality Parameters ◽  
Mosaic Block ◽  
X Ray ◽  
Crystal Imperfections ◽  
Crystal Strain ◽  
Set Up

An analysis is given of the effect of different beam and detector parameters on the sharpness of recorded diffraction features for macromolecular crystals of different quality. The crystal quality parameters include crystal strain, crystal or mosaic block size and mosaic block misorientation. Calculations are given for instrument parameters such as angular resolution of the detector, beam divergence and wavelength bandpass to be matched to the intrinsic diffraction properties from these crystals with the aim of obtaining the best possible data out of each crystal. Examples are given using typical crystal imperfections obtained from the literature for both room-temperature and cryo-cooled crystals. Possible implications for the choice of X-ray source, beamline design, detector specifications, instrument set-up and data processing are discussed, together with the limitations of the approach.

scholarly journals Significance of Fracture-Filling Rose-Like Calcite Crystal Clusters in the SE Pyrenees

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 522
Author(s):  
David Cruset ◽  
Jordi Ibáñez-Insa ◽  
Irene Cantarero ◽  
Cédric M. John ◽  
Anna Travé
Keyword(s):  
Fluid Inclusions ◽  
Aromatic Hydrocarbons ◽  
Major Elements ◽  
Clumped Isotopes ◽  
X Ray Diffraction ◽  
Calcite Crystal ◽  
Fresh Groundwater ◽  
Raman Analysis ◽  
X Ray ◽  
Co2 Release

Fracture-filling rose-like clusters of bladed calcite crystals are found in the northern sector of the Cadí thrust sheet (SE Pyrenees). This unusual calcite crystal morphology has been characterized by using optical and electron microscope, X-ray diffraction, Raman spectroscopy, δ18O, δ13C, 87Sr/86Sr, clumped isotopes, and major and rare earth elements + yttrium (REEs + Y) analysis. Petrographic observations and powder X-ray diffraction measurements indicate that these bladed crystals are mainly made of massive rhombic crystals with the conventional (104) faces, as well as of possibly younger, less abundant, and smaller laminar crystals displaying (108) and/or ( 1 ¯ 08) rhombic faces. Raman analysis of liquid fluid inclusions indicates the presence of aromatic hydrocarbons and occasionally alkanes. Clumped isotopes thermometry reflects that bladed calcite precipitated from meteoric fluids at ~60–65 °C. The 87Sr/86Sr ratios and major elements and REEs content of calcite indicate that these fluids interacted with Eocene marine carbonates. The presence of younger ‘nailhead’ calcite indicates later migration of shallow fresh groundwater. The results reveal that rose-like calcite clusters precipitated, at least in the studied area, due to a CO2 release by boiling of meteoric waters that mixed with benzene and aromatic hydrocarbons. This mixing decreased the boiling temperature at ~60–65 °C. The results also suggest that the high Sr content in calcite, and probably the presence of proteins within hydrocarbons trapped in fluid inclusions, controlled the precipitation of bladed crystals with (104) rhombohedral faces.

scholarly journals Optical Properties of Titanium in the Regime of the Limited Light Penetration

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 952 ◽  
Author(s):  
Lukasz Skowronski
Keyword(s):  
Deposition Time ◽  
Light Penetration ◽  
X Ray Diffraction ◽  
Titanium Film ◽  
X Ray ◽  
Force Microscopy ◽  
Free Carriers ◽  
Plasma Energy ◽  
Atomic Force ◽  
The Mean

In this study, the titanium layers from 12 to 1470 nm thick were fabricated by using the method involving dynamically changed working gas pressure (gas injection magnetron sputtering). The influence of the deposition time on the optical and electrical properties of Ti films, as well as on their microstructure, are considered. The samples are investigated by means of spectroscopic ellipsometry, atomic force microscopy, X-ray diffraction, and confocal optical microscopy. Additionally, for the Ti layers, the sheet resistance was determined. The produced coatings exhibit privileged direction of growth (002). The obtained results show a gradual increase in the mean relaxation time of free-carriers with the increase in the thickness of titanium film. However, the plasma energy exhibits maximum for the coating with the thickness of 93 nm. For such thickness, the lowest value of optical resistivity (about 200 μ Ω cm) was observed. It was found that the dc- and optical resistivity exhibit similar values for titanium films with thickness up to 93 nm. For thicker Ti layers, significant differences in resistivities (dc- and optical) were noticed. The behavior of the Drude parameter (the plasma energy), calculated optical resistivity, and discrepancies between values of optical and dc-resistivities for thicker Ti coatings can be explained as a result of the limited light penetration.

A Study Of Domain Boundary Structures In Lead Titanate Single Crystals

1991 ◽  
Vol 238 ◽  
Author(s):  
C. C. Chou ◽  
J. Li ◽  
C. M. Wayman
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Lead Titanate ◽  
Mixed Type ◽  
Domain Boundary ◽  
Dynamical Theory ◽  
Fringe Contrast ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Contrast Analysis

ABSTRACTDomain boundary structures of flux-grown poly-domain lead titanate single crystals have been studied using transmission electron microscopy. 90° and 180° domain boundaries were seen in the crystals and were systematically analyzed under various diffraction conditions. Although 90° domain boundaries are supposely δ-type boundaries in BaTiO3, our results show that displacement plays an important role at boundaries and the extreme fringe contrast (EFC) behavior of 90° boundaries is of the mixed type. In the present work, an analysis based upon the two beam dynamical theory was conducted and a rule similar to stacking-fault contrast analysis was established to predict the geometric configuration of a 180° domain boundary using EFC behavior. Examples are given and verified by tilting experiments and electron diffraction. The results are consistent and offer a convenient way to distinguish between 90° and 180° boundaries.

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