Preparation of Porous 4H-SiC by Surface Anodization

2005 ◽  
Vol 483-485 ◽  
pp. 257-260 ◽  
Author(s):  
Yi Chen ◽  
Satoko Shoji ◽  
S. Sugishita ◽  
Satoru Ohshima ◽  
Shigehiro Nishino
Keyword(s):  
Current Density ◽  
Electrochemical Etching ◽  
Broad Band ◽  
Low Frequency ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Light Region ◽  
The Fourier Transform ◽  
Porous Sic ◽  
Crucial Parameter

The preparation of porous 4H-SiC by electrochemical etching of SiC crystals was investigated. The porous layer was created at the porous SiC (PSC)/SiC interface but not from the SiC/electrolyte interface. The nanopores at the adjacent region of PSC/SiC interface were bigger than those at the top region. In the visible light region, the optical reflectance from PSC exhibits interference fringes. In the Reststrahlen region, the fourier transform infrared (FTIR) reflectance of porous 4H-SiC shows a splitting into more bands: a broad band with high reflectivity at low frequency and several sharp peaks near the LO frequency. The width and shape of FTIR spectra depended on the anodization current density. The anodization current density is a crucial parameter which determined the porosity, porosity depth profile, and the thickness of PSC layers. A pore transformation of porous structure was observed after chemical vapor deposition process.

Fabrication of Flaky Magnetic Composite Particles

2012 ◽  
Vol 490-495 ◽  
pp. 2628-2631
Author(s):  
Wen Qiang Zhang
Keyword(s):  
Vapor Deposition ◽  
Broad Band ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Complex Permeability ◽  
Composite Particles ◽  
Magnetic Composite ◽  
Frequency Range ◽  
Absorption Properties ◽  
Microwave Absorption Properties

Diatomite coated with ɑ-Fe films were obtained by Chemical Vapor Deposition process. The resultant Fe-coated flaky diatomite particles had low densities. The results show that Fe coated diatomite flakes can be achieved, and that the coating consisted of ɑ-Fe nano-crystallite. The complex permeability and permittivity of the composites were measured in the frequency range of 1–18 GHz. The microwave absorption properties of these flaky particles are discussed. The results indicate that the flaky particles have potential to be used as a lightweight broad band microwave absorber.

Novel Polycrystalline SiC Films Containing Nanoscale Through-Pores by Selective APCVD

2006 ◽  
Vol 527-529 ◽  
pp. 755-758
Author(s):  
L. Chen ◽  
Xiao An Fu ◽  
Christian A. Zorman ◽  
Mehran Mehregany
Keyword(s):  
Atmospheric Pressure ◽  
Polycrystalline Silicon ◽  
Electrochemical Etching ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Porous Structures ◽  
Porous Polycrystalline ◽  
Polycrystalline Silicon Carbide ◽  
Pressure Chemical ◽  
Sic Films

A selective atmospheric pressure chemical vapor deposition (APCVD) process has been developed to deposit porous polycrystalline silicon carbide (poly-SiC) thin films containing a high density of through-pores measuring 50 to 70 nm in diameter. The selective deposition process involves the formation of poly-SiC films on patterned SiO2/polysilicon thin film multilayers using a carbonization-based 3C-SiC growth process. This technique capitalizes on significant differences in the nucleation of poly-SiC on SiO2 and polysilicon surfaces in order to form mechanically-durable, chemically-stable, and well anchored porous structures, thus offering a simple and potentially more versatile alternative to direct electrochemical etching.

A STUDY ON THE PHOTOLUMINESCENCE PROPERTIES OF POROUS 6H-SiC(p) AND SiC FILM ON p-Si SUBSTRATE

2008 ◽  
Vol 22 (06) ◽  
pp. 415-424 ◽  
Author(s):  
K. BOURENANE ◽  
A. KEFFOUS ◽  
M. KECHOUANE ◽  
A. BOURENANE ◽  
G. NEZZAL ◽  
...  
Keyword(s):  
Electrochemical Etching ◽  
Broad Band ◽  
Structure And Properties ◽  
Photoluminescence Properties ◽  
Thin Metallic Film ◽  
Blue Band ◽  
Order Of Magnitude ◽  
P Type ◽  
Porous Sic ◽  
Sic Film

P-type porous SiC layers were fabricated by anodization of a hot-pressed p-type 6H-SiC (30 kΩcm) and a 1.6 μm SiC film was deposited onto p-type Si (100) substrate by Pulsed Laser Deposition (PLD) in HF. In order to facilitate the electrochemical etching of the substrate, ethylene glycol electrolyte has been added to the solution and a thin metallic film of aluminium ( Al ) has been deposited onto a SiC prior to anodization. The structure and properties of the porous SiC layer formed by this method were investigated by Scanning Electron Microscopy (SEM) and Photoluminescence (PL). It shows that photoluminescence spectra exhibit two emission bands centered at 2.20 eV (blue band) and an extended broad band from 2.20 to 3.22 eV (green band) from porous 6H-SiC (PSC). On the contrary, porous thin 1.6 μm SiC layer exhibits only a blue band centered at 2.95 eV. Finally, the results indicate clearly that porous SiC gives off green and blue light. Also, there is a shift to blue luminescence with the same order of magnitude when using a thin SiC layer deposited onto silicon (p- Si (100)).

scholarly journals DC and radio-frequency transmission characteristics of double-walled carbon nanotubes-based ink

2010 ◽  
Vol 2 (5) ◽  
pp. 471-477 ◽  
Author(s):  
Sébastien Pacchini ◽  
Emmanuel Flahaut ◽  
Norbert Fabre ◽  
Véronique Conédéra ◽  
Fabien Mesnilgrente ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Propagation Constant ◽  
Low Frequency ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Network Layers ◽  
Transmission Parameters ◽  
Glycol Solution ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

In this paper, double-walled carbon nanotubes (DWNTs) network layers were patterned using inkjet transfer printing. The remarkable conductive characteristics of carbon nanotubes (CNTs) are considered as promising candidates for transmission line as well as microelectronic interconnects of an arbitrary pattern. In this work, the DWNTs were prepared by the catalytic chemical vapor deposition process, oxidized and dispersed in ethylene-glycol solution. The DWNTs networks were deposited between electrodes contact and then characterized at DC through current–voltage measurements, low frequency, and high frequency by scattering parameters measurements from 40 MHz up to 40 GHz through a vector network analyzer. By varying the number of inkjet overwrites, the results confirm that the DC resistance of DWNTs networks can be varied according to their number and that furthermore the networks preserve ohmic characteristics up to 100 MHz. The microwave transmission parameters were obtained from the measured S-parameter data. An algorithm is developed to calculate the propagation constant “γ”, attenuation constant “α” in order to show the frequency dependence of the equivalent resistance of DWNTs networks, which decreases with increasing frequency.

An advanced electrical heating technique for double-sided Y(Gd)BCO coated conductor: gaining high engineering current density based on MOCVD

2021 ◽  
Vol 34 (12) ◽  
pp. 125018
Author(s):  
Fan Yang ◽  
Ruipeng Zhao ◽  
Bowan Tao ◽  
Xi Chen ◽  
Tao Huang ◽  
...  
Keyword(s):  
Current Density ◽  
Electrical Contact ◽  
Chemical Vapor ◽  
Electric Heating ◽  
Deposition Process ◽  
Electrical Heating ◽  
Organic Chemical ◽  
Substrate Thickness ◽  
Electrical Stability ◽  
Heating Device

Abstract An advanced electrical heating technique was proposed and adopted for the reel-to-reel deposition of double-sided Gd x Y1−x Ba2Cu3O7−δ (Y(Gd)BCO) films on the surface of LaMnO3/epitaxial-MgO/IBAD-MgO/Y2O3/Al2O3/Hastelloy tapes based on the metal organic chemical vapor deposition process. In this technique, heating current is introduced into alloy tape to produce heat through the electric brushes. The use of thin Hastelloy tapes is an effective method to obtain a high engineering current density. However, the reduction of the substrate thickness will directly attenuate its mechanical strength, which will lead to the deformation of tapes at high temperature based on original electric heating device. More seriously, the electrical contact between the alloy substrate and the brush will deteriorate, which could cause ignition and ablation at the edge of the tapes. Therefore, in order to improve mechanical and electrical stability, we redesigned a novel electrical heating device to deposit Y(Gd)BCO films. Furthermore, through adopting the multiple-deposition process based on the new electrical heating device, the J e of Y(Gd)BCO film can reach 900 A mm−2 (at self-field, 77 K), which has been significantly improved compared with the J e before optimization.

Reaction couples of ceramic thin films prepared by CVD

1988 ◽  
Vol 46 ◽  
pp. 798-799
Author(s):  
D.W. Susnitzky ◽  
S.R. Summerfelt ◽  
C.B. Carter
Keyword(s):  
Thin Film ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Solid State Reactions ◽  
Spatial Distributions ◽  
Diffusion Couples ◽  
Kinetics Studies ◽  
Ceramic Thin Films ◽  
Initial Stage

Solid-state reactions have traditionally been studied in the form of diffusion couples. This ‘bulk’ approach has been modified, for the specific case of the reaction between NiO and Al2O3, by growing NiAl2O4 (spinel) from electron-transparent Al2O3 TEM foils which had been exposed to NiO vapor at 1415°C. This latter ‘thin-film’ approach has been used to characterize the initial stage of spinel formation and to produce clean phase boundaries since further TEM preparation is not required after the reaction is completed. The present study demonstrates that chemical-vapor deposition (CVD) can be used to deposit NiO particles, with controlled size and spatial distributions, onto Al2O3 TEM specimens. Chemical reactions do not occur during the deposition process, since CVD is a relatively low-temperature technique, and thus the NiO-Al2O3 interface can be characterized. Moreover, a series of annealing treatments can be performed on the same sample which allows both Ni0-NiAl2O4 and NiAl2O4-Al2O3 interfaces to be characterized and which therefore makes this technique amenable to kinetics studies of thin-film reactions.

Microstructural characterization of YBa2Cu3O7-x thin films formed by metalorganic CVD

1991 ◽  
Vol 49 ◽  
pp. 1080-1081
Author(s):  
P. Lu ◽  
W. Huang ◽  
C.S. Chern ◽  
Y.Q. Li ◽  
J. Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Film Growth ◽  
Chemical Vapor ◽  
Microstructural Characterization ◽  
Ion Milling ◽  
Conventional Grinding

The YBa2Cu3O7-x thin films formed by metalorganic chemical vapor deposition(MOCVD) have been reported to have excellent superconducting properties including a sharp zero resistance transition temperature (Tc) of 89 K and a high critical current density of 2.3x106 A/cm2 or higher. The origin of the high critical current in the thin film compared to bulk materials is attributed to its structural properties such as orientation, grain boundaries and defects on the scale of the coherent length. In this report, we present microstructural aspects of the thin films deposited on the (100) LaAlO3 substrate, which process the highest critical current density.Details of the thin film growth process have been reported elsewhere. The thin films were examined in both planar and cross-section view by electron microscopy. TEM sample preparation was carried out using conventional grinding, dimpling and ion milling techniques. Special care was taken to avoid exposure of the thin films to water during the preparation processes.

Determination of creep mechanisms in various silicon carbides via TEM

1986 ◽  
Vol 44 ◽  
pp. 484-487
Author(s):  
C. H. Carter ◽  
J. E. Lane ◽  
J. Bentley ◽  
R. F. Davis
Keyword(s):  
Heat Exchangers ◽  
Sintered Material ◽  
Polycrystalline Material ◽  
Chemical Vapor ◽  
Graphite Substrate ◽  
Second Phase ◽  
Reaction Bonding ◽  
Creep Mechanisms ◽  
Porous Sic

Silicon carbide (SiC) is the generic name for a material which is produced and fabricated by a number of processing routes. One of the three SiC materials investigated at NCSU is Norton Company's NC-430, which is produced by reaction-bonding of Si vapor with a porous SiC host which also contains free C. The Si combines with the free C to form additional SiC and a second phase of free Si. Chemical vapor deposition (CVD) of CH3SiCI3 onto a graphite substrate was employed to produce the second SiC investigated. This process yielded a theoretically dense polycrystalline material with highly oriented grains. The third SiC was a pressureless sintered material (SOHIO Hexoloy) which contains B and excess C as sintering additives. These materials are candidates for applications such as components for gas turbine, adiabatic diesel and sterling engines, recouperators and heat exchangers.

Contact Current Density Analysis Inside Human Body in Low-Frequency Band Using Geometric Multi-Grid Solver

2020 ◽  
Vol E103.C (11) ◽  
pp. 588-596
Author(s):  
Masamune NOMURA ◽  
Yuki NAKAMURA ◽  
Hiroo TARAO ◽  
Amane TAKEI
Keyword(s):  
Frequency Band ◽  
Current Density ◽  
Human Body ◽  
Low Frequency ◽  
Density Analysis
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