bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Filtration System to Control Urban Non-Point Pollution
Authors: Kim Seog Ku , Kim Young Im , Lee Byung Cheol , Kang Sung Won , Kang Bong Moon , Kwak Pill Jae , Ahn Jae Hwan
Published: March 2009

Runoff from bridge impermeable surface is discharged directly into the receiving river or
sewage pipe. However, generally, a bridge does not have sufficient space to place some treatment
system. In this study, therefore, we investigated the down-flow filtration using expended
polypropylene media (EPM) to treat runoff from bridge. Experiments were conducted employing
down-flow filtration column (dh, 50600mm) to investigate the removal efficiency of pollutants.
The EPM5, EPM10, EPM15 and f-EPM10 filters were developed from high molecular material, and
were classified by different foaming rates and present of functional material. The experiment using
f-EPM10 showed good hydraulic filtration performance without overflow for 1hr. But overflow, in
the experiments using EPM5, EPM10 and EPM15, was observed within 1hr. Since f-EPM contains
functional material, that can be improved water flow without clogging. The total SS removal
efficiency of filtration equipment was rapidly decreased after overflow. In addition, a down-flow
experiment, having slope of 15°, to avoid SS deposition at top of the column was carried out. Though
SS deposition was found to be similar in two types flow, the flow of down-flow experiment, having
slope of 15°, made progress without overflow for 3hr. This is because deposited SS didn’t intercept
water inflow.
High-Aspect-Ratio Titanium Oxide Nanotubes Anodized in KH2PO4/NH4F/Citric Acid Electrolytes
Authors: Cho Seong Je , Kim Jong Oh , Yang Dae Jin , Choi Won Youl
Published: March 2009

Titanium of 99.7% purity was anodized in 1M potassium phosphate monobasic
(KH2PO4) water solution with 0.15M NH4F. Titanium oxide nanotubes were fabricated at
anodization potential of 20 V and 4.64 pH. To control the pH of the solution, we have added weak
acid such as citric acid because it has three dissociation constants (pKa) of 3.09, 4.75, and 5.41.
Citric acid was very useful to control the pH of the 1M KH2PO4 water electrolyte solution within 3
to 5. The diameter and length of the titanium oxide nanotubes were independent on anodization
time. The diameter of 120 nm and length of 2.8 μm at anodization time of 5 hrs were observed by
field emission scanning electron microscope (FESEM). Undesired thin oxide layer blocking the top
of titanium oxide nanotubes was wiped out by increasing the anodization potential with the multi
step voltage by 1 V reached to 25 V. The titanium oxide nanotubes having a very large surface area
are very attractive for the battery, gas sensor, photocatalytic application, and biomaterials.
Characterization and Fabrication of Nano-Sized Patterns and Microfluidic Channels Derived from Polyvinylsilazane via Soft Lithographic Technique
Authors: Lee Hong Joo , Park Jun Hong , Jayakumar Perumal , Yoon Tae Ho , Hong Lan Young , Park Sang Hee , Kim Dong Pyo
Published: March 2009

Interests on the fabrication of microfluidic devices have increased in the fields of micro
total analysis system (μ-TAS) and MEMS (Microelectromechanical systems) due to their chemical
inertness and high thermal stability. The thermal characterization of the SiCN preceramic polymer,
polyvinylsilazane, showed that the cured polymer has ceramic properties at heat treatment
temperature of 600 oC or above. In the characterization of the mechanical properties, the characteristic
values of the elastic modulus and hardness notably increased for the heat-treated SiCN. The present
study describes the preparation of nano-sized patterns and microfluidic channels using a soft
lithographic technique. The study shows that the fabrication of microchannels using the cured
inorganic polymers holds tremendous potential in the field of microfluidics, where materials with
high optical transparency, thermal stability and chemical inertness are in demand as niche between
conventional microfluidics using glass and polymeric materials.
Direct Electroless Copper Plating on Polyimide for FPCB Applications
Authors: Lee Jae Ho
Published: March 2009

As electronic devices are getting smaller and lighter, the density of copper lines on
flexible printed circuit board (FPCB) is getting higher. Conventionally, subtractive method was used
for copper line on a flexible films, however, as the line pitch is getting smaller, the lateral etching of
copper cause serious problem. To replace the subtractive method, semi-additive method was used
for fine pitch copper line fabrication. In semi additive process, sputtered layer for the
electroplating copper was required. The feasibility of electroless plating to replace high cost
sputtered copper seed layer was investigated. Electroless depositions of copper were conducted on
different substrate to find optimum conditions of electroless copper plating. To find optimum
conditions, the effects and selectivity of activation method on several substrates were also
investigated. The adhesion strength between polyimide and copper was improved by treating the
polyimide surface with butylamines. Pretreatment prior to electroless plating is very sensitive and
surface dependent. Surface morphologies were investigated with FESEM.
Effects of Post-Annealing on the Electrical and Optical Properties of ZnO Thin Films Grown on Al2O3 Substrates by Atomic Layer Epitaxy
Authors: Lee Chong Mu , Cho Young Joon , Kim Ho Jin , Lee Wang Woo , Kim Hyoun Woo , Hwangbo Chang Kwon , Lee Jae Gab
Published: March 2009

Influence of nitrogen and oxygen annealing atmospheres on the carrier concentration,
carrier mobility, electrical resistivity and PL characteristics as well as the crystallinity of ZnO films
deposited on sapphire substrates by atomic layer deposition (ALD) were compared. X-ray
diffraction (XRD) and photoluminescence (PL) analyses, and Hall measurement were performed to
investigate the crystallinity, optical properties and electrical properties of the ZnO thin films,
respectively. The UV emission intensity for oxygen annealing is stronger than that for nitrogen
annealing in the case of annealing at 600°C, but the difference decreases with the Increase of
annealing temperature. The strongest UV emission is obtained by oxygen annealing at 800°C.
However, from the viewpoint of electrical resistivity annealing at 1,000°C in either an oxygen or a
nitrogen atmosphere is more desirable. Taking both the PL and electrical properties into
consideration it may be concluded that optimum annealing condition for ZnO thin films grown on
the sapphire substrate by ALD is an annealing temperature of 900°C and an annealing atmosphere
of oxygen although the effects of annealing atmosphere on the optical and electrical properties are
not so significant.
Oxidation of IG-11 Graphite by Air and CO2 Gas
Authors: Lim Yun Soo , Lee Ji Na , Kim So Yeon , Kim Tae Wan , Chi Se Hwan
Published: March 2009

Artificial graphite generally manufactured by carbonization sintering of shape-body of
Kneaded mixture using granular cokes as filler and pitch as binder, going through pitch
impregnation process if necessary and finally applying graphitization heat treatment. The effect of
thermal oxidation with air or CO2 atmosphere on IG-11 graphite samples was investigated. The
results show a localized oxidation process which progressively reveals the large coke particles with
increasing overall weight loss in air. The surface of graphite was peel off which was not changed
the specific gravity after air oxidation. However, the specific gravity of graphite continuously
decreased by CO2 oxidation. Decreasing of specific gravity in the CO2 oxidation was because that
CO2 gas ingress the surface to interior. The pore shape after the CO2 oxidation showed the longneck
beakers.
Preparation and Characterization of Alumina Nanoparticles from Alkoxides and Na (AOT) Surfactant
Authors: Park Yong Kap
Published: March 2009

Nanosized α-aluminum oxides have been prepared by hydrolysis of aluminum alkoxides
using a sol-gel procedure. The Na(AOT) as a surface active agent was added into the alumina
precursor solution to investigate the influence on size and morphology of alumina particles. The
product phase was mainly boehmite with mean particle size of 20~30 nm. The crystal phases and
morphology of the alumina nanoparticles were analyzed by X-ray diffractometry and by
transmission electron microscopy, respectively. The TEM observations revealed that α-Al2O3 with
about 80 nm spherical and hexagonal shapes was formed after calcination at 1200oC. The TG/DSC
analyses were also done to determine the phase changes of alumina precursors from room
temperature to 1200oC.
Inhibition Effects of Inorganic and Polymer Coagulants on Acidogenic Fermentation
Authors: Kim Jong Oh , Jung Jong Tae
Published: March 2009

Laboratory-scale batch experiments were conducted to investigate the possible inhibition of acidogenic
volatile fatty acids (VFAs) fermentation by an inorganic and a polymer coagulant. It was found that the conversion from
organic matter to VFAs decreased more than 10% when the dosages of coagulant exceeded 46 (mgAl/L) and 120
(mgFe/L). Inhibition by Al was greater than that Fe. When the dosage of polymer was over 102 (mg/L), VFAs
conversion fell to below 2%. The protein content was more affected than the carbohydrate content. Ultrasonic treatment
increased the VFAs conversion for synthetic sludge at both treated with either inorganic coagulant or polymer
Spark Plasma Sintering Behavior of Fe-TiC Composite Materials Fabricated by Mechanical Alloying
Authors: Cho Ho Jung , Bae Sung Yeal , Ahn In Shup , Park Dong Kyu
Published: March 2009

TiC-based cermets attract much attention because of their excellent wear-resistance, high
hardness at high temperature, good chemical stability, superior thermal deformation resistance.
Therefore, titanium carbide is mainly used for cutting tools, grinding wheels, coated cutting tips and
coated steel tools. In this research, Fe-TiC composite materials were fabricated by spark plasma
sintering (SPS) after mechanical alloying. TiH2 and graphite powders were used to synthesize TiC
phase. In order to compare the properties of sintered materials using mixture powder
(D’AE+TiH2+graphite), commercial TiC powder was mixed with Distaloy AE (D’AE) powder as a
same mechanical alloying method. Then, the shape of each mixture powder (D’AE+TiH2+graphite,
D’AE+TiC (commercial)) and sintering properties were compared. TiC phase was synthesized by
self-propagating high-temperature synthesis (SHS) reaction during spark plasma sintering. It was
confirmed by using X-ray diffraction (XRD). Energy dispersive spectrometry (EDS) and Scanning
electron microscopy (SEM) were used to observe shape of mixture powders and also sintering
properties were examined such as hardness, relative density. In case of sintered material for 10min
holding time at 1373K after mechanical alloying for 1 hour with D’AE, TiH2 and graphite, it indicated
higher hardness value 49HR-C than a case using D’AE and TiC powder.
Study on Non-Destructive Testing of Aerial Complex Material by DSPI
Authors: Jia Shu Hai , Li Yi Gui
Published: March 2009

A novel method to examine the defect of aerial complex material is presented in this
paper. The novel speckle averaging technique for DSPI static measurement is proposed to improve
the quality of measurement. A speckle averaging mechanism is designed and fabricated. The
measurement result of sandwich structure material of practical aviation engineering is presented.
The defect in the final results is clear.
A Study on Vacuum Plasma Spraying Tungsten Coatings
Authors: Yi Zeng , Zheng Xue Bin , Ji Heng , Wu Wei , Lee Soo Wohn
Published: March 2009

The W coatings were prepared by applying the vacuum plasma spraying process (VPS). The phase
composition, microstructure and laser irradiation property were characterized by XRD, SEM and laser.
Results showed that no tungsten oxide appears in the coatings whose phase composition is similar to the
original powder. A better melting state of the coating can be obtained by using the finer powder. The
deposition efficiency of the coating is higher in the cases of a higher H2 flow. There is a pitch whose size is
about 100μm when the substrate was irradiated by laser. However, there is clearly no change for the W
coating surface which was also irradiated under the same condition. It indicates that the laser irradiation
resistance is improved significantly for stainless steel after being deposited with W coating.
Synthesis and Characterization of Ag-Pd Nanoparticles by a Reverse Micelle Process
Authors: Bae Dong Sik , Kang Sung , Park Kyu Seop , Han Kyong Sop
Published: March 2009

Preparation of Ag-Pd nanoparticles by the reduction of AgNO3 and PdCl2 with
hydrazine in Igepal CO-520/cyclohexane reverse micelle solutions was studied. An analysis
by transmission electron microscope and electron diffraction spectrum revealed that the
resultant particles are silver-palladium. The average size of the synthesized nanoparticles
slightly changed with increases in the molar ratio of water to Igepal CO 520. The average size
of the synthesized nanoparticles was below 5 and they were broadly distributed.
Synthesis and Characterization of CoFe2O4 Nanoparticles by Glycothermal Process
Authors: Lee Chil Soon , Bae Dong Sik
Published: March 2009

CoFe2O4 nanoparticles were prepared in ethylene glycol solution under mild
temperature and pressure conditions by precipitation from metal nitrates. The average
size of the synthesized CoFe2O4 nanoparticles was in the range of 5 to 10, and they
were narrowly distributed in the crystalline phase. Their magnetic property was of
superparamagnetic character at room temperature. The effect of synthesis parameters is
discussed such as the pH of starting solutions and reaction temperature.
Nano-Al2O3 Reinforced Fe-Cr-Ni Composites Fabricated by Reactive Hot Pressing
Authors: Chen Chang , Yu Ting , Yang Jian Feng , Gao Ji Qiang , Jin Zhi Hao , Niihara Koichi
Published: March 2009

Based on low-temperature hot-press sintering and rapid thermit reaction, heat-resistant
metal matrix composites with nano-ceramic reinforcement were prepared via reactive hot pressing.
According to XRD, the composites comprised predominantly of (fcc) Cr0.19Fe0.7Ni0.11, (fcc) Fe-Cr
and alumina at 700°C through the highly-exothermic thermit reaction between the starting powders.
Three-point bending strength, fracture toughness, Vickers hardness and relative density increased
with the increase of hot-press sintering temperature and holding time. The improving mechanical
properties may be explained by increasing of content of (fcc) Cr0.19Fe0.7Ni0.11. SEM analysis showed a
microstructure consisting of equiaxial granules at 700°C for 1 h and a uniformly dispersed network of
very fine grains at 700°C for 2 h. It is considered that, in the reactive hot-pressing process, Al atoms
diffused into the metal matrix (Fe2O3, Cr, Ni) sites and formed Al2O3 and Fe-Cr-Ni matrix. Such a
technique offers the possibility of synthesizing heat-resistant metal matrix composites with
nano-ceramic reinforcement materials at considerably lower temperature.
Recovery of Silica and Sodium Fluoride from Hexafluorosilicic Acid and Sodium Silicate
Authors: Kim Jong Kil , Park Jin Koo , Kim Ho Kun
Published: March 2009

A process for the recovery of nanoporous silica and sodium fluoride from
hexafluorosilicic acid and sodium silicate under the different molar ratios was studied. In order to
prepare the appropriate solutions of initial compounds 25% of hexafluorosilicic acid and the 18% of
sodium silicate were used. Obtained nanoporous silica and sodium fluoride have been characterized
by XRD, BET, TGA, EDX and SEM.
Effect of Metal Additives (Co and Ni) on the Electrochemical Properties of Lithium/FeS2 Batteries
Authors: Choi Jae Won , Cheruvally Gouri , Ahn Jou Hyeon , Kim Ki Won , Ahn Hyo Jun
Published: March 2009

Iron, sulfur and transition metal powders were used as the starting materials to prepare iron
disulfide (FeS2) cathode material at room temperature by high energy mechanical alloying. Modified
FeS2 were also prepared by incorporation of transition metals like Co and Ni. Li/FeS2 cells with the
prepared iron disulfides as cathodes were studied for discharge properties at room temperature using
the 0.5M LiTFSI in tetra(ethylene glycol) dimethyl ether (TEGDME). The first discharge capacities
of Li/composite FeS2 cell with 5 wt.% Co and 3 wt.% Ni were 571 and 844 mAh/g, respectively,
compared to 389 mAh/g for the cell without any additive. The enhanced properties resulted from the
better electronic conductivity of the material containing the metallic additive. The initial capacity and
cyclic performance were improved when nickel and cobalt were added to prepare the modified iron
disulfide.
Ion Implanted AZ31 Magnesium Alloy
Authors: Wu Guo Song , Zeng Xiao Qin , Yao Shou Shan , Han Hai Bo
Published: March 2009

Ion implantation was applied to modify the surface properties of magnesium alloy. About
75 keV titanium ions with a dose of 5×1017 ions/ cm-2 and about 35 keV nitrogen ions with a dose of
3×1017 ions/ cm-2 were implanted into AZ31 magnesium alloy, respectively. AFM and FESEM were
used to examine the surface morphology of the treated samples. In contrast to the smooth surface
treated by N ion implantation, the Ti-treated surface was severely damaged. AES analysis reveals that
both kinds of ions implanted in AZ31 magnesium alloy took on a quasi-Gaussian distribution in the
near surface region. In the corrosion test, the N-implanted sample showed a better corrosion
resistance in 3.5wt.% NaCl solution than bare AZ31 sample, whereas the Ti-implanted sample
accelerated the corrosion behavior of AZ31 in this solution
Grain Refinement of an Al-Cu-Mg Alloy by Microalloying and Common Thermo-Mechanical Treatment
Authors: Wu Bao Lin , Sha Gui Ying , Wang Yi Nong , Zhang Yu Dong , Esling Claude
Published: March 2009

Heavy deformation plus micro alloying could be an effective way to obtain ultrafine grain
structure of metals. In the present work, an Al-Cu-Mg alloy was microalloyed with Zr to obtain
homogeneous precipitates and then heavily deformed by conventional forging at high temperature.
The possible refining processing routes were studied and the superplasticity behaviors of the alloy
was investigated. Results show that the micro alloyed alloy can be stably refined to 3-5μm under
conventional processing routes. The Al-3Zr precipitates act both as additional sites to enhance
recrystallization nucleation rate and pins to impede grain growth to increase the thermal stability of
the fine grain structure. However, as the Al3Zr precipitates remains along grain boundaries, the
superplastic capability of the material is not high. At 430°C with 1×10-4S-1 strain rate, the elongation
obtained was 260%.
The Dislocation Patterns in Deformed Metals: Dislocation Densities, Distributions and Related Misorientations
Authors: Rauch Edgar F. , Shigesato G.
Published: March 2009

The dislocation substructure that appears in deformed metals and alloys have been extensively investigated in the past by transmission electron microscopy (TEM). They are known to form a broad variety of microstructures. These substructures are characterized by three main parameters, namely the density of the dislocations that are trapped in the tangles, their degree of patterning and the misorientation between the cells. The aim of the present work is to investigate the relationship between these features and the mechanical properties of the material.
Ultra-Fine Grained High Carbon Steel by Innovative Deformation
Authors: Smith A.W.F. , Crowther D.N. , Apps P.J. , Prangnell Philip B.
Published: March 2009

It is well known that the refinement of grain size in metals leads to a significant
improvement in specific mechanical properties. Processing schedules have been investigated aimed
at producing an homogeneous ultra-fine ferrite and spheroidised carbide aggregate microstructure in
high carbon (CMn) steels (0.6-1.2wt%C), via conventional ‘warm’ rolling and innovative Equal
Channel Angular Extrusion (ECAE). Suitable deformation schedules were determined from
dilatometry and thermo-mechanical Gleeble simulations. Evidence of an ultra-fine ferrite and
carbide aggregate microstructure following ‘warm’ rolling was observed. A significant
improvement in tensile strength, particularly proof stress was also noted in comparison to material
deformed at higher temperatures. Concurrent ECAE experiments investigated microstructural
evolution with incremental strain. Extensive analysis was carried out using various techniques,
including high resolution Electron Back Scattered Diffraction (EBSD). Evidence of ferrite grain
refinement was noted in a eutectoid composition steel. A sub-micron ferrite structure was observed
following high strains (ε~3.33) and the mechanical properties exhibited a marked increase in tensile
strength.
Hele-Shaw Model for Melting/Freezing with Two Dendrits
Authors: Rogosin Sergei , Vaitekhovich Tatsyana
Published: March 2009

Melting/freezing process with two dendrits (or freeze “pipes”) is modelled by the
complex Hele-Shaw moving boundary value problem in a doubly connected domain. The later is
equivalently reduced to a couple of problems, namely, to the linear Riemann-Hilbert boundary
value problem in a doubly connected domain and to evolution problem, which can be written
in a form of an abstract Cauchy-Kovalevsky problem. The later is studied on the base of
Nirenberg-Nishida theorem, and for the former a generalization of the Schwarz Alternation
Method is proposed. By using composition of these two approaches we get the local in time
solvability of this couple of problems in appropriate Banach space setting.
Corrosion Resistance of β-SiAlON-Based Ceramics Against Molten Steel
Authors: Šajgalík Pavol , Křest'an J. , Lenčéš Zoltán
Published: March 2009

The corrosion resistance of sialons made from commercial powders (AlN, Al2O3 and Si3N4) and from powder precursor produced by carbothermal reduction and nitridation of raw aluminosilicate (pyrophyllite) in molten steel were investigated. The corroded zone in sialon made from raw pyrophyllite (P1) is more then two times deeper compared to the corroded zone of sialon made from commercial powders (C1). The corrosion zone of sample P1 is on the average 610 μm deep, while in sample C1 it is only 260 μm. The main corrosion products are γ-Al2O3 and iron silicides. The phase compositions were estimated by neutron Rietveld refinement.
Aqueous Processing of AlN Powder
Authors: Krnel Kristoffer , Kosmač Tomaž
Published: March 2009

For the production of ceramics containing AlN as a major or minor constituent it is necessary to avoid hydrolysis. To do that, non-aqueous powder processing is required or waterresistant AlN powders must be used. Alternatively, as in the Hydrolysis Assisted Solidification (HAS) process, which exploits the hydrolysis of the AlN for the solidification of the ceramic suspensions, the hydrolysis has to be prevented at room temperature but initiated at elevated temperatures. In this work a systematic study of AlN powder reactivity in water and other aqueous environments is presented. The AlN hydrolysis was investigated by measuring the pH of diluted suspensions and by analysis of the reaction products. The results indicate possible solutions for control of the reaction with water in order to exploit it or to prevent it to enable aqueous AlN powder processing.
Effect of Fluorine and Nitrogen Anions on Properties of Ca-Si-Al-O Glasses
Authors: Genson Annaik , Hanifi Amir R. , Put A.Vande , Pomeroy Michael J. , Hampshire Stuart
Published: March 2009

The preparation of bulk glasses in Ca-Si-Al-O-N-F system with the composition in equivalent % of 28e/oCa:56e/oSi:16e/oAl:100-X-Ye/oO:Xe/oF:Ye/oN are reported. The glass formation behaviour and properties of this new range of glasses are examined in detail. Fluorine decreases the glass transition temperature, the density and the mechanical properties of the glasses while nitrogen increases them. Therefore, it appears that fluorine acts as a network modifier while, on the contrary, nitrogen acts as a network former even in presence of fluorine.
Jasminaldehyde Synthesis Catalyzed by Al(Ga)PON Oxynitrides: Influence of the Reaction Conditions
Authors: Hasni M. , Rouchaud J. , Grange P. , Devillers M. , Delsarte S.
Published: March 2009

Nitridation of amorphous aluminium phosphate (AlPO4) and mixed aluminium gallium phosphate (Al0.5Ga0.5PO4) under ammonia flow allows preparing “AlPON” and “AlGaPON” bifunctional acid-base heterogeneous catalysts. Their acid-base bi-functional character allows their use as selective catalysts for the production of jasminaldehyde through the cross-condensation of heptanal and benzaldehyde, followed by the dehydration of the aldol intermediate product. Three parameters enabling to maximize the jasminaldehyde yields in a batch reactor operated at 125°C were investigated: the catalyst composition (Al/Ga and O/N ratio), the reactant concentration and the amount of catalyst in the reactor. Maximum jasminaldehyde selectivities were obtained for intermediate nitrogen contents (7-10 wt.%). Maximum reaction rates were obtained using pure reactants and a catalysts weight equal to 10% of the total reagent weight.
The New Top-To-Bottom Method of SiAlON Precursor Preparation by Activation in a Planetary Mill with a High Acceleration
Authors: Sopicka-Lizer Malgorzata , Tańcula Marta , Pawlik Tomasz , Kochnev V , Fokina E.
Published: March 2009

Nano-structured β-sialon precursor powders were obtained as a result of milling in a
planetary mill with a high acceleration. Various mixtures of initial nitrides/oxides have been
prepared as β-sialon precursor with low (0.4-1.0z) substitution and were milled in a planetary mill
of acceleration 28g (TTD, Russia) with zirconia or silicon nitride balls for a various times (30-45
min). The resultant powder showed various extents of crystalline lattice deformation: smaller
crystallites, dislocations, bumpy surface. The degree of lattice destruction was influenced by the
milling time and grinding media, however various mixture components showed diverse
susceptibility to deformation.
Proposed Architecture for SiC Switches and Diodes in a Switch Mode Power Supply
Authors: Hancock Jon M.
Published: March 2009

This SiC diodes and switches provide greatly enhanced performance at higher operating
voltage, but the base material provides a high barrier to adoption in commercial systems. Commercial
adoption has not occurred by adopting SiC components in place of Si devices, but only when
the characteristics of SiC components can successfully leverage system performance and cost. Doing
so requires a close look at current roadblocks and examining topologies and techniques that can
bring more optimal system performance (density, efficiency, cost) with SiC components. High density
converters using conventional components are becoming limited by the volume and cost of passive
components, particularly the EMI filters and bulk filter capacitors. To address this and demonstrate
the performance capabilities of SiC in SMPS, a PWM isolation converter is proposed using
the resonant reset forward converter in an interleaved configuration. This topology can extend energy
recovery from the primary bulk bus capacitor used for hold up time, as well as minimizing filtering
requirements for input and output capacitors. The interleaved converter is developed from
cascode switches using experimental SiC JFETs, in a configuration derived from previous work
with a single switch converter. Overall performance as well as design issues will be discussed.
Very High Growth Rate Epitaxy Processes with Chlorine Addition
Authors: La Via Francesco , Leone Stefano , Mauceri Marco , Pistone Giuseppe , Condorelli Giuseppe , Abbondanza Giuseppe , Portuese F. , Galvagno G. , Di Franco Salvatore , Calcagno Lucia , Foti Gaetano , Valente Gian Luca , Crippa Danilo
Published: March 2009

The growth rate of 4H-SiC epi layers has been increased by a factor 19 (up to 112 μm/h)
with respect to the standard process with the introduction of HCl in the deposition chamber. The
epitaxial layers grown with the addition of HCl have been characterized by electrical, optical and
structural characterization methods. An optimized process without the addition of HCl is reported
for comparison. The Schottky diodes, manufactured on the epitaxial layer grown with the addition
of HCl at 1600 °C, have electrical characteristics comparable with the standard epitaxial process
with the advantage of an epitaxial growth rate three times higher.
Initial Growth in 3C-SiC Sublimation Epitaxy on 6H-SiC
Authors: Syväjärvi Mikael , Sritirawisarn Nut , Yakimova Rositza
Published: March 2009

The effect of initial growth condition of 3C-SiC growth on the C-face of 6H-SiC has
been studied in sublimation epitaxy. The initial temperature increase to initiate the sublimation has a
strong effect on the polytype formation using on-axis substrates. Polytype inclusions of 6H-SiC in
the 3C-SiC layers is found to be related to spiral growth. The micropipe dissociation process is
discussed. At the slowest ramp-up of the temperature the 3C-SiC does not contain any inclusions. In
1 degree off-oriented substrates there were no 3C-SiC formation. In this case the different ramp-up
conditions has an influence on the heights of the steps.
Mosaicity and Wafer Bending in SiC Wafers as Measured by Double and Triple Crystal X-Ray Rocking Curve and Peak Position Maps
Authors: Kirchner K.W. , Jones Kenneth A. , Derenge Michael A. , Dudley Michael , Powell Adrian R.
Published: March 2009

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.
Distinction of the Nuclei of Shockley Faults in 4H-SiC{0001} pin Diodes by Electroluminescence Imaging
Authors: Ishii R. , Miyanagi Toshiyuki , Kamata Isaho , Tsuchida Hidekazu , Nakayama Koji , Sugawara Yoshitaka
Published: March 2009

We investigated the location of the nuclei of Shockley-type stacking faults (SSFs) in the
4H-SiC pin diodes, using electroluminescence (EL) imaging. The nuclei of SSFs were identified as
three types, located (i) on the mesa edge, (ii) in the surface region, and (iii) inside the epilayer. We
compared the frequency of the nuclei according to these three locations for the (0001) and (000-1) pin
diodes. The number of SSFs originated from the nuclei inside the epilayer in the (000-1) pin diodes
was much less (<4 cm-2) than that in the (0001) pin diodes. However, the numbers of SSF nuclei (0.3
~ 0.8 per device) located on the mesa wall and the surface region in the (000-1) pin diodes were
comparable to the (0001) pin diodes. We also investigated the process responsible for generating the
SSF nuclei.
Impact of n-Type versus p-Type Doping on Mechanical Properties and Dislocation Evolution during SiC Crystal Growth
Authors: Wellmann Peter J. , Hens Philip , Sakwe Sakwe Aloysius , Queren Desirée , Müller Ralf , Durst Karsten , Göken Matthias
Published: March 2009

The origin of dislocation evolution during SiC crystal growth is usually related to lattice
relaxation mechanisms caused by thermal stress. In this paper we discuss dislocation generation and
dislocation propagation related to doping and suppression of basal plane dislocations, the latter
being of particular interest for bipolar electronic devices. We have prepared alternating p-/n-/pdoped
SiC crystals using the donor nitrogen and the acceptors aluminum or boron. In addition we
determined the mechanical properties of n-type and p-type SiC; in particular we measured the
critical shear stress by nano-indentation on c-plane and a-plane 6H-SiC surfaces. A considerably
lower basal plane dislocation density is found in aluminum as well as in boron doped p-type SiC
compared to nitrogen doped n-type SiC. It is concluded that the explanation of the reduced basal
plane dislocation density in p-type SiC needs the consideration of electronic as well as mechanical
effects.
Properties of Thermally Etched 4H-SiC by Chlorine-Oxygen System
Authors: Hatayama Tomoaki , Takenami S. , Yano Hiroshi , Uraoka Yukiharu , Fuyuki Takashi
Published: March 2009

By the use of Cl2-O2 thermal etching method, the etching rates of 4H-SiC were reached
to about 1μm/h for Si and 40μm/h for C face at 950oC. Etch pits only appeared over 0.25-μm-etched
depth on the 4H-SiC (0001) Si face. The shapes and density of etch pits are similar tendencies in the
case of molten KOH etched surface. To study the relationship between thermally etched surface
features and crystal defects, the planar mapping electron-beam-induced current (EBIC) technique
was carried out. Almost dark areas in the EBIC image correspond to the etch pits. From the EBIC
image, a shell-like pit formed by the Cl2-O2 etching on the (0001) Si face is a basal plane
dislocation.
Whole-Wafer Mapping of Dislocations in 4H-SiC Epitaxy
Authors: Stahlbush Robert E. , Liu Kendrick X. , Zhang Q. , Sumakeris Joseph J.
Published: March 2009

A non-destructive technique to image the dislocations and other extended defects in SiC
epitaxial layers has been developed. Basal plane dislocations (BPDs) and threading dislocations
(TDs) are imaged. Photoluminescence from the dislocations is excited with the 364 and/or 351 nm
lines of an argon ion laser and near-infrared light is collected. A computer controlled probe station
takes multiple images and the mm-sized images are stitched together to form whole-wafer maps.
The technique is applied to a set of four n+ wafers from the same boule with 50 um n- epitaxial
layers. The epitaxy was grown with Cree’s low-BPD process. BPDs form as either single, isolated
dislocations or as clusters encircling micropipes. The concentration of TDs is on the order 104/cm2
and the local concentration varies more than an order of magnitude. The advantages of mapping
dislocations by UV-PL imaging compared to other techniques are discussed.
Electrical and Structural Properties of Al-Implanted and Annealed 4H-SiC
Authors: Obernhofer M. , Krieger M. , Schmid Frank , Weber Heiko B. , Pensl Gerhard , Schöner Adolf
Published: March 2009

Aluminum ions (Al+) were implanted at room temperature or at 500°C into n-type 4HSiC.
The implantation damage (displaced Si atoms) and the electrical activation of Al+ ions
(concentration of Al acceptors) were determined by Rutherford backscattering in channeling mode
and Hall effect, respectively, as a function of the annealing temperature.
Growth and Electrical Characterization of 4H-SiC Epilayers
Authors: Kimoto Tsunenobu , Danno Katsunori , Hori T. , Matsunami Hiroyuki
Published: March 2009

Homoepitaxial growth of 4H-SiC and characterization of deep levels obtained mainly in
the authors’ group have been reviewed. The growth rate has been increased to 24 om/h with keeping
very good surface morphology and low trap concentration on 8o off-axis 4H-SiC(0001) by hot-wall
chemical vapor deposition at 1650oC. The increased growth rate has resulted in the enhanced
conversion of basal-plane dislocations into threading edge dislocations in epilayers. The Z1/2 and
EH6/7 concentrations can be decreased to about 1·1012 cm-3 by increasing the C/Si ratio during CVD.
Extensive investigation on as-grown and electron-irradiated epilayers indicates that both the Z1/2 and
EH6/7 centers may be attributed to the same origin related to carbon displacement, probably a carbon
vacancy. Deep levels observed in as-grown and irradiated p-type 4H-SiC are also presented.
Electric-Field Screening Effects in the Micro-Photoluminescence Spectra of As-Grown Stacking Faults in 4H-SiC
Authors: Juillaguet Sandrine , Guillet T. , Bardoux R. , Camassel Jean , Chassagne Thierry
Published: March 2009

We report a comparison of continuous-wave photoluminescence spectra with spatiallyresolved
micro-photoluminescence data collected at low temperature on as-grown stacking faults in
a 4H-SiC epitaxial layer. We find that the defects have a large triangular shape
(50 μm x 50 μm x 50 μm) and that the maximum signal wavelength shifts when scanning across
one triangular defect. These results show that the built-in electric field in the stacking fault well can
be screened, more or less depending on the incoming light intensity.
Photoluminescence of 6H-SiC Nanostructures
Authors: Botsoa Jacques , Bluet Jean Marie , Lysenko Vladimir , Marty Olivier , Barbier Daniel , Guillot Gérard
Published: March 2009

Photoluminescence properties of a freestanding nanoporous SiC layer obtained from bulk
6H-SiC substrate as well as SiC nanopowder consisting of numerous separated nanoparticles has
been investigated. The nanoporous SiC layer is obtained by UV radiation assisted electrochemical
etching of the 6H-SiC wafer and the SiC nanopowder is formed by mechanical grinding of the
nanoporous SiC free layer. A comparison of low temperature PL spectra of the SiC nanostructures
and initial SiC bulk substrate has been performed. The evolution of PL spectra of the SiC
nanostructures with respect to their surface states and excitation laser power has been studied. In
particular, the well pronounced high energy tail above the excitonic bandgap in the PL spectra of
the nanostructured SiC is attributed to quantum confinement effects. The strong PL signal obtained
below the bandgap is explained by radiative transitions involving surface states, N-Al donoracceptor
recombination levels and deep levels corresponding to volume defects in the SiC
nanocrystallites.
Ellipsometric and MEIS Studies of 4H-SiC/Si/SiO2 and 4H-SiC/SiO2 Interfaces for MOS Devices
Authors: Guy Owen James , Jenkins T.E. , Lodzinski Michal , Castaing A. , Wilks S.P. , Bailey P. , Noakes T.C.Q.
Published: March 2009

The high density of interface states of thermally grown oxides on silicon carbide has
prompted research into alternative oxidation methods and post oxidation anneals. One such
alternative is oxidation of a deposited sacrificial silicon layer. A recent variation of this technique is
a partial oxidation of the deposited Si layer, so that a thin Si layer remains between the SiO2 and
SiC layers. If the SiO2/Si interface has lower interface state densities than the SiO2/SiC interface,
the SiO2/Si/SiC hetero-structure could yield improved channel mobilities in MOS devices.
Moreover, by correct optimization of the MOSFET device structure, breakdown can be designed to
occur in the bulk SiC layer, thus maintaining a high blocking voltage. Post oxidation annealing in
N2O is another technique often used to reduce interface state densities. However, little is known
about the chemical and physical nature of these N2O oxidized dielectrics. Ellipsometric and
Medium Energy Ion Scattering (MEIS) investigations of conventional SiO2/SiC interfaces
compared with SiO2/Si/SiC hetero-junction structures and N2O oxidized samples are reported.
4H-SiC Epitaxial Layers Grown on On-Axis Si-Face Substrate
Authors: ul Hassan Jawad , Bergman Peder , Henry Anne , Pedersen Henrik , McNally Patrick J. , Janzén Erik
Published: March 2009

We report on the growth of 4H-SiC epitaxial layer on Si-face polished nominally on-axis 2” full
wafer, using Hot-Wall CVD epitaxy. The polytype stability has been maintained over the larger part
of the wafer, but 3C inclusions have not been possible to avoid. Special attention has given to the
mechanism of generation and propagation of 3C polytype in 4H-SiC epilayer. Different optical and
structural techniques were used to characterize the material and to understand the growth
mechanisms. It was found that all 3C inclusions were generated at the interface between the
substrate and the epitaxial layer, and no 3C inclusions were initiated at later stages of the growth.
Modification of Surface Layer during High Temperature Annealing and its Effects on the SiC Diode Characteristics
Authors: Bahng Wook , Cheong Hui Jong , Kang In Ho , Kim Seong Jin , Kim Sang Cheol , Joo Sung Jae , Kim Nam Kyun
Published: March 2009

We have investigated the influence of surface modification on the electrical properties of
SiC diodes. Schottky diodes (SBDs) as well as PiN diodes were fabricated on n-type SiC substrate
with an epilayer, and electrically characterized before and after high temperature annealing, and after
removing the surface modified layer, respectively. The devices annealed without graphite cap layer
showed ohmic behavior. The surface layer was modified to a conductive layer possibly due to the
preferred sublimation of Si species. In order to confirm the existence of modified surface conductive
layer, diode was fabricated on the same substrate and electrically characterized after removing
30nm-thick damaged layer by ICP-RIE. The leakage current reduced dramatically, as much as 7
orders of magnitude. The PiN diodes fabricated on the damaged surface layer showed the reverse
leakage current and the breakdown voltage of 50mA and 1250V, respectively. While those of the
diode fabricated after removing the damaged surface layer were 200nA at the breakdown voltage of
2100V, respectively.
Use of Graphite Cap to Reduce Unwanted Post-Implantation Annealing Effects in SiC
Authors: Oliviero Erwan , Lazar Mihai , Vang Heu , Dubois Christiane , Cremillieu Pierre , Leclercq Jean Louis , Dazord Jacques , Planson Dominique
Published: March 2009

6H and 4H–SiC epilayers were Al-implanted at room temperature with multiple energies
(ranging from 25 to 300 keV) in order to form p-type layers with an Al plateau concentration of
4.5×1019 cm-3 and 9×1019 cm-3. Post-implantation annealing were performed at 1700 or 1800 °C up
to 30 min in Ar ambient. During this process, some samples were encapsulated with a graphite (C)
cap obtained by thermal conversion of a spin-coated AZ5214E photoresist. From Atomic Force
Microscope measurements, the roughness is found to increase drastically with annealing
temperature for unprotected samples while the C capped samples show a preservation of their
surface states even for the highest annealing temperature. After 1800°C/30 min annealing, the RMS
roughness is 0.46 nm for the lower fluence implanted samples, slightly higher than for unimplanted
samples (0.31 nm). Secondary Ion Mass Spectroscopy measurements confirm that the C cap was
totally removed from the SiC surface. The total Al-implanted fluence is preserved during postimplantation
annealing. A redistribution of the Al dopants is observed at the surface which might be
attributed to Si vacancy-enhanced diffusion. An accumulation peak is also observed after annealing
at 0.29 9m, depth corresponding to the amorphous/crystalline interface that was determined on the
as-implanted samples by Rutherford Backscattering Spectroscopy in channeling mode. The
redistribution of the dopants has an impact on their electrical activation. A lower sheet resistance
(Rsh= 8 k) is obtained for samples annealed without capping than for samples annealed with
C capping (Rsh= 15 k ).
4H-SiC Metal-Oxide-Semiconductor (MOS) Capacitors Fabricated by Oxidation in a Tungsten Lamp Furnace in Combination with a Microwave Plasma and Subsequent Deposition of Al2O3
Authors: Beljakowa Svetlana , Frank Thomas , Pensl Gerhard , Gao Kun Yuan , Speck Florian , Seyller Thomas
Published: March 2009

An alternative oxidation technique is developed and built up, which provides monatomic
oxygen during the whole oxidation process. The set-up consists of a tungsten lamp furnace and a
microwave-plasma. A number of different gases can be introduced into the oxidation quartz tube. In
addition, an Al2O3-layer is deposited on a part of the oxide layers by atomic layer chemical vapor
deposition (ALCVD). First oxidation runs result in encouraging low values of the density of
interface states Dit and in the flatband voltage UFB. It turns out that with the present experimental
conditions, the comparison of MOS capacitors fabricated with different dielectric layers favors gate
dielectrics grown in O2/N2-ambient.
A Comparative Study of Surface Passivation on SiC BJTs with High Current Gain
Authors: Lee Hyung Seok , Domeij Martin , Zetterling Carl Mikael , Östling Mikael , Sveinbjörnsson E.Ö.
Published: March 2009

The effect of the different types of passivation layers on the current gain of SiC BJTs has
been investigated. Measurements have been compared for BJTs passivated with thermal SiO2,
plasma deposited (PECVD) SiO2 and BJTs without passivation. The maximum DC current gain of
BJTs with thermal SiO2 was about 62 at IC=20 mA and Vce=40 V. On the other hand, the BJTs with
a passivation by PECVD SiO2 had a DC current gain of only 25. The surface recombination current
was extracted from measurements with BJTs of different emitter widths. The surface recombination
current of BJTs with a thermally grown oxide was about 25 % lower than unpassivated BJTs and
65 % lower than that of PECVD passivated BJTs.
Electronic Structure of Graphite/6H-SiC Interfaces
Authors: Seyller Thomas , Emtsev Konstantin V. , Speck Florian , Gao Kun Yuan , Ley Lothar
Published: March 2009

We have studied the electronic structure of the interface between 6H-SiC{0001} and
graphite. On n-type and p-type 6H-SiC(0001) we observe Schottky barriers of ÁSi
b,n = 0.3±0.1
eV and ÁSi
b,p = 2.7±0.1 eV, respectively. The observed barrier is face specific: on n-type 6H-
SiC(0001) we find ÁC
b,n = 1.3±0.1 eV. The impact of these barriers on the electrical properties
of metal/SiC contacts is discussed.
Nanolayered Au/Ti/Al Ohmic Contacts to P-Type SiC: Electrical, Morphological and Chemical Properties Depending on the Contact Composition
Authors: Kolaklieva Lilyana , Kakanakov Roumen , Avramova Iva , Marinova Ts.
Published: March 2009

Electrical, morphological and chemical properties of nanolayered Au/Ti/Al ohmic
contacts with different Ti:Al ratio are investigated. Contact resistivities of 1.42×10-5 ⋅cm2 and
1.21×10-5 ⋅cm2 are achieved for Au/Ti(70)/Al(30) and Au/Ti(30)/Al(70) contacts, respectively. It
is found that the Ti:Al ratio does not affect the lowest resistivity value but influences on the optimal
annealing temperature at which it is obtained. The different optimal annealing temperature provokes
different element distributions and interface chemistry of the annealed contacts. An increase of the
Al concentration in the contact composition causes essentially the surface morphology leading to an
increase in surface roughness of the as-deposited and annealed contacts.
Low Output Capacitance 1500V 4H-SiC MOSFETs with 8 mΩ·cm2 Specific On-Resistance
Authors: Matocha Kevin , Tucker Jesse , Arthur Steve , Schutten Michael , Nasadoski Jeff , Glaser John , Stevanovic Ljubisa
Published: March 2009

SiC MOSFETs are characterized with a specific on-resistance of 8 m⋅cm2 at room
temperature and a blocking voltage of 1500 V. Due to the negative shift in the threshold voltage,
devices typically show a reduction in on-resistance with temperature. However, this work shows
that a positive resistance temperature coefficient can be achieved by proper device design. SiC
MOSFETs were characterized for use in high-frequency resonant converters, where an important
switching device figure of merit is the product of the device on-resistance and output capacitance
(Ron×Coss). For devices with an active area of 3.6×10-3 cm2, the output capacitance is 12.5 pF at a
drain bias of 270V. Thus, these device achieve a resonant converter figure of merit Ron×Coss =
28 ⋅pF at room temperature and 34 ⋅pF at 150°C, better than commercial silicon superjunction
devices operating at the same temperatures.