bluuebunny/crossref_metadata_2025 huggingface dataset:
Rietveld Refinement of Crystal Phases (Ca1-xLax)MnO3 with Perovskite-Type Structure
Authors: Dukić Jelena , Bošković Snezana , Matović B. , Dimčić B. , Karanović Lj.
Published: March 2009

Two nanopowders with nominal compositions (Ca0.7La0.3)MnO3 (CLM) and
(Ca0.7La0.3)(Mn0.8Ce0.2)O3 (CLMC) were synthesized by a modified glycine/nitrate procedure. XRD
analysis revealed binary phase mixture in both samples. The influence of La and Ce on unit cell
parameters, atom positions, and average bond distances were analyzed. According to these results
and refined occupation factors of La and Ca, as well as quantitative phase analysis it was found that
the CLM sample consists of 85 mass.% of Ca0.62La0.38MnO3 and 15 mass.% of Ca0.99La0.01MnO3,
while the CLMC sample consists of 70 mass.% of Ca0.58La0.42MnO3 and 30 mass.% of CeO2.
Microstructure size-strain analysis was performed and the Rietveld refinement gave crystallites of
about 100 Å. TEM images showed particle sizes of about 100-500 Å.
Synthesis of ZnO and ZrO2 Powders by Mechanochemical Processing
Authors: Čeliković Ana , Kandić Ljiljana , Zdujić M. , Uskokovic Dragan P.
Published: March 2009

The ZnO and ZrO2 powders were prepared by mechanochemical processing and
subsequent heat treatment of the starting powder of precursors mixture of ZnCl2 and Ca(OH)2, and
ZrOCl2·8H2O and NaOH, respectively. Inert salt matrix, ether CaCl2 or NaCl, which prevents
particle agglomeration was formed during mechanochemical solid state reaction. After
mechanochemical treatment, samples were calcined at various temperatures. Selective removal of
the matrix phase by washing the resulting powder with appropriate solvent yields almost pure ZnO
and ZrO2 powders. Characterization of the powders was performed by X-ray diffraction (XRD),
differential thermal and thermo gravimetric analysis (DTA−TG) and scanning electron microscopy
(SEM).
Preparation of ZrO2 and Al2O3 Thin-Films on Stainless Steel by Spray Pyrolysis
Authors: Novaković T. , Radić Nenad , Grbić Boško , Stoychev Dimitar , Stefanov Plamen , Marinova Ts.
Published: March 2009

We have investigated the deposition of ZrO2 and Al2O3 films on a stainless steel (SS)
substrate by spray pyrolysis method. The ZrO2 films were deposited from aqueous solution of
zirconium dinitrate oxide. For Al2O3 films, a boehmite sol was used. The specific surface areas of
samples were determined by the BET-method and sample surfaces were characterized by scanning
electron microscopy and X-ray photoelectron spectroscopy. The spray pyrolysis method permits the
preparation of ZrO2 and Al2O3 thin films on SS with good adhesion. This method enables
preparation of oxide layers with relatively high specific surface area, suitable for applications as
catalysts supports.
Ion Implantation Induced Modifications in Reactively Sputtered Cr-N Layers on Si Substrates
Authors: Novaković M. , Popović M. , Peruško D. , Radović I. , Milinović V. , Milosavljević M.
Published: March 2009

We present a study of the micro-structural changes induced in Cr-N layers by irradiation
with argon ions. The layers were deposited by reactive ion sputtering on (100) Si wafers, to a
thickness of 240-280 nm, at different nitrogen partial pressures and different substrate temperatures.
The samples were subsequently irradiated with 120 keV Ar+, to 1x1015 and 1x1016 ions/cm2.
Structural characterization was performed with Rutherford backscattering spectroscopy, x-ray
diffraction analysis and transmission electron microscopy, and we also did electrical resistivity
measurements on the samples. It has been found that the layers grow in the form of a polycrystalline
columnar structure, with a columnar width of a few tens of nm. The layer composition, Cr2N or
CrN, strongly depends on the nitrogen partial pressure during deposition. Ion irradiation induces
local micro-structural changes, formation of nano-particles and defects, though the structures retain
their polycrystalline nature. The induced crystalline defects yield an increase of electrical resistivity
after ion irradiation.
Sol-Gel Elaboration and Optical Features of Eu3+-Doped CdS Nanocrystals in SiO2
Authors: Julián B. , Planelles J. , Cordoncillo E. , Escribano P. , Sanchez C. , Aschehoug P. , Viana Bruno , Pellé Fabienne
Published: March 2009

In this work, Eu3+-doped CdS nanocrystals embedded in a SiO2 matrix were synthesised
by a sol-gel method since this method confers a great chemical homogeneity, and allows in-situ
generation and controlled growth of CdS nanocrystals within the silica glass. The influence of the
sol-gel conditions on the Eu3+ optical response has been investigated. The synthesis conditions can
be varied to modify the structure of the material, and the dispersion of the rare earth ion, within the
silica matrix. From the optical analysis an energy transfer appears from CdS nanoparticles to Eu3+
ions but also a back transfer Eu3+ to CdS nanoparticles is evidenced.
Synthesis, Characterization and Biological Activity Evaluation of Novel Pd(II) and Pt(II) Complexes with Heterocyclic Hydrazone Ligands
Authors: Filipović Nenad R. , Todorović Tamara R. , Sladić D.M. , Novaković Irena T. , Jeremić D.A. , Andjelković K.K.
Published: March 2009

New complexes of Pt(II) with condensation derivatives of ethyl hydrazinoacetate and
either 2-acetylpyridine or 2-quinolinecarboxaldehyde, and of Pd(II) with the condensation
derivative of ethyl hydrazinoacetate and 2-quinolinecarboxaldehyde were synthesized and
characterized by elemental analysis, IR, 1H- and 13C-NMR spectroscopy, and molar conductivity
measurements. The complexes have a square planar geometry, ligands binding as bidentates in the
neutral form, and the remaining two coordination sites being occupied by chloride ions. Biological
activity of new complexes, and of previously synthesized Pd(II), Cd(II), Co(III) and Zn(II)
complexes with this ligand type was evaluated by the brine shrimp test. All the complexes showed a
moderate activity.
Particle-In-Cell Modelling of a Neutral Beam Source for Material Processing in Nanoscale Structures Fabrication
Authors: Radmilović-Radjenović M. , Petrović Z.Lj. , Nikitović Željka , Strinić A. , Stojanović V. , Nina Aleksandra , Radjenović B.
Published: March 2009

Neutral beam processing has evolved into one of the most promising methods for
overcoming plasma process induced damage. Surface treatment by neutrals avoids problems with
surface charging effects, frequently encountered when using common ion treatment, especially for
low k-materials. In this paper, the influence of various parameters on the neutralization of ion
beams in Ar-CF4 mixture based on a Particle in Cell with Monte Carlo collisions (PIC/MCC)
simulation is studied. The efficiency of neutralization has been treated by considering both
surface neutralization of ions and collisions of ions in the gas.
Effect of Silane Coupling Agents on Mechanical Properties of Nano-SiO2 Filled High-Density Polyethylene Composites
Authors: Stojanović D. , Uskoković P. S. , Balać I. , Radojević V.J. , Aleksić R.
Published: March 2009

Composites with nano-SiO2 particles and high density polyethylene (HDPE) matrix were
produced by hot pressing with various particle contents and particle surface treatment using
commercially available silane coupling agents: γ-methacryloxypropyltrimethoxy silane and γ-
glycidyloxypropyltrimethoxysilane. The influence of the particle treatment on the mechanical
properties of composites was determined by compression and indentation tests. Additionally,
numerical analysis was performed in order to calculate Young’s modulus and stress concentrations
for various particle contents in order to provide reference data by simulating micro- and macro
particle composites with perfect bonding to the matrix.
The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite
Authors: Miličević Dejan , Trifunović S. , Ignjatović N. , Suljovrujić E.
Published: March 2009

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been
widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma
irradiation has been successfully employed in the modification/sterilization of such porous
composites and that it has advantages over other procedures. In this study, differential scanning
calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass
transition behavior and structural relaxation, as well as to estimate the activation energy for this
process. The apparent activation energy ΔH* for structural relaxation in the glass transition region
was determined on the basis of the heating rate dependence of the glass transition temperature Tg.
Furthermore, the results were correlated with those obtained by gel permeation chromatography
(GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is
the main reason for the decrease of the glass transition temperature and/or activation energy with
the absorbed dose.
Delamination Strain Energy Release Rate in Carbon Fiber/Epoxy Resin Composites
Authors: Gordić M.V. , Djordjević I.M. , Sekulić D.R. , Petrović Z.S. , Stevanović M.M.
Published: March 2009

The paper reports on an experimental study of the Mode I interlaminar fracture of
unidirectional carbon fibers/epoxy resin composites. Mode I delamination strain energy release rate
GIC was determined in double cantilever beam (DCB) test, before and after gamma irradiation at
various doses. Glass transition temperature, Tg of epoxy matrix was determined from dynamic
mechanical measurements. The delamination surfaces of tested coupons were observed by scanning
electron microscopy. The variations in GIC values were correlated with irradiation doses, Tg values
and the features of delamination microfractographs, as well as with the variation under irradiation
of matrix or fibre/matrix dominated mechanical properties.
Microstructure and Microhardness in Current Annealed Fe65.5Cr4Mo4Ga4P12C5B5.5 Bulk Metallic Glass
Authors: Mitrović N. , Čukić B. , Jordović Branka , Roth Stefan , Stoica M.
Published: March 2009

The rods of Fe-based bulk metallic glasses with the nominal composition
Fe65.5Cr4Mo4Ga4P12C5B5.5 were cast by melt injection into 1.5 and 1.8 mm diameter copper molds.
The thermal stability, microstructure and crystallization behavior were investigated by differential
scanning calorimetry, optical micrography and X-ray diffraction, respectively. The wide
supercooled liquid region between crystallization temperature (Tx) and glass transition temperature
(Tg) in the as-cast state Tx=Tx-Tg=60 K, as well as the high value of reduced glass transition
temperature Trg=Tg/Tl=0.567 (Tl is liquidus temperature) approves enhanced thermal stability of the
alloy against crystallization. In the as-cast “XRD-amorphous” state, microhardness HV1=742 was
observed. Multistep current annealing thermal treatments were performed for structural relaxation.
After applying high enough heating power per square area (PS ≥ 6 W/cm2), intensive crystallization
of the samples characterized by appearance of several iron-metalloid compounds (Fe5C2, Fe3Ga4,
Fe63Mo37 and Mo12Fe22C10) was observed. The microstructure changes after crystallization bring
about differences in the microhardness values. The areas of still present amorphous matrix are with
increased value HV1=876, but a remarkable decrease to HV1=323 was observed in precipitated
crystallized zone that propagate along inner part of cylinders.
The Effect of Temperature on the Magnetic Properties of the Electrochemically Obtained Ni92.8 Mo7.2 Powder Pressed at Different Pressures
Authors: Ribić-Zelenović L. , Simeunović R. , Maričić A. , Spasojević M.
Published: March 2009

The Ni92.8Mo7.2 alloy powder was obtained by electrochemical codeposition from an
ammonium solution of NiSO4 and (NH4)6 Mo7O24 at j = 100 mA m-2, on a titanium cathode. DSC
measurements and determination of the dependence of electrical resistivity on temperature did not
reveal any changes in powder structure in the temperature range from 293 to 460 K. Therefore, in
this range, there was no significant change in magnetic susceptibility either. Structural relaxation
took place in the temperature interval from 460 to 560 K causing an increase in magnetic
susceptibility. At temperatures higher than 570 K, magnetic susceptibility rapidly decreased. The
Curie temperature of the powder was 660 K. With the increasing powder pressing pressure the
magnetic susceptibility increased while the electric resistivity decreased. With the pressing pressure
increase, the pore size was decreased and a better contact between powder particles was established.
This caused electrical resistivity decrease and magnetic susceptibility increase.
The Role of Intermetallic Phases in Fatigue Crack Propagation Behavior of Al-Zn-Mg-Cu Alloys
Authors: Vratnica M. , Cvijović Z. , Gerić K. , Burzić Zijah
Published: March 2009

The aim of the present work is to determine the role of intermetallic (IM) phases in the
fatigue crack propagation behavior of hot-forged Al-Zn-Mg-Cu alloys in T73 condition. To
generate differences in the volume fraction and coarseness of various IM particles, the (Fe+Si)
impurity level is varied from 0.23 to 0.37 mass%. The fatigue crack propagation tests are conducted
in air at ambient temperature and a stress ratio R of 0.1. Characterization of the fatigue fracture
surfaces is performed using scanning electron microscopy (SEM) and energy-dispersive X-ray
spectroscopy (EDS). Quantified IM particles data for each alloy are then related to the fatigue
properties and fractographic analysis results. It was found that almost all particles of the Fecontaining
phases (primarily (Cu,Fe,Mn)Al3 and Al7Cu2Fe) are broken and not effective in
hindering fatigue crack propagation. On the other hand, the Mg2Si and soluble phase particles
smaller than those of the Fe-containing phases contribute beneficially to fatigue life. These particles
increase the tortuosity of the crack path and retard the crack growth rate. The crack growth rate
decreases as the volume fraction of coarse Fe-containing particles increases, because more
secondary cracks are produced decreasing the effective stress intensity at the main crack tip.
Equivalent Circuits of Unipolar Pulsed Plasma System for Electrical and Optical Signal Analysis
Authors: Popović I. , Zlatanović M.
Published: March 2009

Matching of pulse plasma generators to various gas discharges for surface treatment of
materials depends on plasma processing equipment. In order to investigate the influence of pulse
plasma generator and gas discharge parameters on electrical signal waveforms during the process of
unipolar pulse plasma nitriding, equivalent electrical circuit was introduced. The influence of
parasitic inductance of interconnection lines and vacuum chamber physical properties was also
included in the given equivalent circuit. Gas discharge characteristics at different process
parameters were investigated. It was found that the gas discharge and pulse plasma generator
properties, as well as the electrical characteristics of interconnecting lines determined the system
electrical signal response. From the analysis of optical signals emitted by the gas discharge it was
found that the optical signal response might be represented by a typical RC integrator circuit
response with the time constant higher than that of the equivalent electrical circuit of generator load.
The conclusion was drawn that the process of charge particles generation is followed by the process
of active species generation responsible for thermo-chemical processes on the cathode surface.
Thus, the increase of the pulse plasma frequency is limited by the thermo-chemical process
efficiency, and not only by the generator switching characteristics or by gas discharge electrical
properties.
OBIC Analysis of Different Edge Terminations of Planar 1.6 kV 4H-SiC Diodes
Authors: Raynaud Christophe , Loup Daniel , Godignon Philippe , Rodriguez Raul Perez , Tournier Dominique , Planson Dominique
Published: March 2009

High voltage SiC semiconductor devices have been successfully fabricated and some of
them are commercially available [1]. To achieve experimental breakdown voltage values as close as
possible to the theoretical value, i.e. value of the theoretical semi-infinite diode, it is necessary to
protect the periphery of the devices against premature breakdown due to locally high electric fields.
Mesa structures and junction termination extension (JTE) as well as guard rings, and combinations
of these techniques, have been successfully employed. Each of them has particular drawbacks.
Especially, JTE are difficult to optimize in terms of impurity dose to implant, as well as in terms of
geometric dimensions. This paper is a study of the spreading of the electric field at the edge of
bipolar diodes protected by JTE and field rings, by optical beam induced current.
Hot Electron Induced Current Collapse in AlGaN/GaN HEMTs
Authors: Nakajima Akira , Yagi Shuichi , Shimizu Mitsuaki , Adachi Kazuhiro , Okumura Hajime
Published: March 2009

The mechanism of drain current collapse in AlGaN/GaN high electron mobility transistors
(HEMTs) was investigated. Current collapse was clearly observed for TiO2 passivated HEMTs.
However, no evidence of current collapse was apparent for SiNx passivated HEMTs. This suggests
that AlGaN surface traps play a major role in current collapse. The experimental results were
compared with numerical device simulation results. The device simulations were performed taking
into account hot electron generation and deep traps at the AlGaN surface. The simulated drain current
transients were consistent with the degradation and recovery behavior of the experimental results.
These results indicate that current collapse is caused by the trapping of hot electrons in deep levels at
the AlGaN surface.
Homoepitaxial Growth of 4H-SiC Multi-Epilayers and its Application to UV Detection
Authors: Liu Xing Fang , Sun Guo Sheng , Zhao Yong Mei , Ning Jin , Li J.Y. , Wang Lei , Zhao Wan Shun , Luo M.C. , Li Jin Min
Published: March 2009

Homoepitaxial growth of 4H-SiC p+/π/n- multi-epilayer on n+ substrate and in-situ doping
of p+ and π-epilayer have been achieved in the LPCVD system with SiH4+C2H4+H2. The surface
morphologies, homogeneities and doping concentrations of the n--single-epilayers and the p+/π/n-
multi-epilayers were investigated by Nomarski, AFM, Raman and SIMS, respectively. AFM and
Raman investigation showed that both single- and multi-epilayers have good surface morphologies
and homogeneities, and the SIMS analyses indicated the boron concentration in p+ layer was at least
100 times higher than that in π layer. The UV photodetectors fabricated on 4H-SiC p+/π/n-
multi-epilayers showed low dark current and high detectivity in the UV range.
Low Trap Concentration and Low Basal-Plane Dislocation Density in 4H-SiC Epilayers Grown at High Growth Rate
Authors: Hori T. , Danno Katsunori , Kimoto Tsunenobu
Published: March 2009

Fast homoepitaxial growth of 4H-SiC has been carried out on off-axis (0001) substrates by
horizontal hot-wall CVD at 1600οC. High growth rate up to 24 μm/h has been achieved with
mirror-like surface in the C/Si ratio range of 1.0-2.0. The Z1/2 and EH6/7 concentrations can be kept as
low as 7 × 1011 cm-3 and 3 × 1011 cm-3, although an unknown trap (UT1) is observed with the
concentration in the 1011 cm-3 range. The photoluminescence spectra are dominated by strong free
exciton peaks, and the L1 peak is not observed. The basal-plane dislocation (BPD) density has
decreased with increase in growth rate, and it can be reduced to 22 cm-2 when epilayers are grown on
Chemical Mechanically Polished (CMP) substrates at a growth rate of 24 μm/h.
Optimisation of Epitaxial Layer Growth with HCl Addition by Optical and Electrical Characterization
Authors: Calcagno Lucia , Izzo Gaetano , Litrico Grazia , Galvagno G. , Firrincieli A. , Di Franco Salvatore , Mauceri Marco , Leone Stefano , Pistone Giuseppe , Condorelli Giuseppe , Portuese F. , Abbondanza Giuseppe , Foti Gaetano , La Via Francesco
Published: March 2009

High growth rate of 4H-SiC epitaxial layers can be reached with the introduction of HCl
in the deposition chamber. The effect of the Cl/Si ratio on this epitaxial growth process has been
studied by optical and electrical measurements. Optical microscopy shows an improvement of the
surface morphology and luminescence measurements reveal a decrease of epitaxial layer defects
with increasing the Cl/Si ratio in the range 0.05–2.0. The leakage current measured on the diodes
realized on these wafers is reduced of an order of magnitude and DLTS measurements show a
decrease of the EH6,7 level concentration in the same range of Cl/Si ratio. The value Cl/Si=2.0
allows to grow epitaxial layers with the lowest defect concentration.
SiC Epitaxial Layers Grown by Sublimation Method and their Electrical Properties
Authors: Park Chi Kwon , Lee Gi Sub , Lee Ju Young , Kyun Myung Ok , Lee Won Jae , Shin Byoung Chul , Nishino Shigehiro
Published: March 2009

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was
adopted to produce thick SiC epitaxial layers for power device applications. In this study, we aimed to
systematically investigate surface morphologies and electrical properties of SiC epitaxial layers
grown with varying a SiC/Al ratio in a SiC source powder during the sublimation growth using the
CST method. It was confirmed that the acceptor concentration of epitaxial layer was continuously
decreased with increasing the SiC/Al ratio. The blue light emission was successfully observed on a
PN diode structure fabricated with the p-type SiC epitaxial layer. Furthermore, 4H-SiC MESFETs
having a micron-gate length were fabricated using a lithography process and their current-voltage
performances were characterized.
Heavily Doped Polycrystalline 3C-SiC Growth on SiO2/Si (100) Substrates for Resonator Applications
Authors: Sun Guo Sheng , Ning Jin , Liu Xing Fang , Zhao Yong Mei , Li Jia Ye , Wang Lei , Zhao Wan Shun , Wang Liang
Published: March 2009

3C-SiC is a promising material for the development of microelectromechanical systems
(MEMS) applications in harsh environments. This paper presents the LPCVD growth of heavily
nitrogen doped polycrystalline 3C-SiC films on Si wafers with 2.0 μm-thick silicon dioxide (SiO2)
films for resonator applications. The growth has been performed via chemical vapor deposition
using SiH4 and C2H4 precursor gases with carrier gas of H2 in a newly developed vertical CVD
chamber. NH3 was used as n-type dopant. 3C-SiC films were characterized by scanning electron
microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), secondary
ion mass spectroscopy (SIMS), and room temperature Hall Effect measurements. It was shown that
there is no voids at the interface between 3C-SiC and SiO2. Undoped 3C-SiC films show n-type
conduction with resisitivity, Hall mobility, and carrier concentration at room temperature of about
0.56 ⋅cm, 54 cm2/Vs, and 2.0×1017 cm-3, respectively. The heavily nitrogen doped polycrystalline
3C-SiC with the resisitivity of less than 10-3 ⋅cm was obtained by in-situ doping. Polycrystalline
SiC resonators have been fabricated preliminarily on these heavily doped SiC films with thickness
of about 2 μm. Resonant frequency of 49.1 KHz was obtained under atmospheric pressure.
Comparative Investigation between X-Ray Diffraction and Cross Polarization Mapping of 4H-SiC Wafers Off-Cut 4° Towards (11-20)
Authors: Gaskill D. Kurt , Mastro Michael E. , Lew Kok Keong , VanMil Brenda L. , Myers-Ward Rachael L. , Holm Ronald T. , Eddy Charles R.
Published: March 2009

A set of three 4H-SiC wafers with manufacturer specified micropipe density of 0-5 cm-2
were characterized by x-ray diffraction (XRD) maps before and after final chemical-mechanical
polish. After final polish, the wafers were also investigated with atomic force microscopy, radius of
curvature measurements and cross-polarization (x-pol) mapping. It was found that there was largely
a lack of correlation between the XRD and x-pol maps, which strongly suggests that x-pol is insensitive
to crystalline imperfections to which XRD is sensitive.
Defect Etching of Non-Polar and Semi-Polar Faces in SiC
Authors: Sakwe Sakwe Aloysius , Jang Yeon Suk , Wellmann Peter J.
Published: March 2009

Wet chemical etching using molten KOH is the most frequently applied method to reveal
structural defects in SiC. Until now etching kinetics of SiC in planes different from the polar cplane
has not been reported. In this paper we report on defect etching of SiC in non-polar faces. Using
a calibrated KOH defect-etching furnace with possibilities to set accurate etching temperatures
we have etched SiC samples of various orientations to (i) study defect occurrence and their morphologies
(ii) set KOH defect etching parameters for SiC for these orientations and (iii) investigate
etching kinetics in relation to anisotropy/surface polarity. For non-polar planes of the same orientations
a comparison in etching kinetics and defect morphologies in crystals grown in different directions
is presented.
Influence of Growth Temperature on the Evolution of Dislocations during PVT Growth of Bulk SiC Single Crystals
Authors: Sakwe Sakwe Aloysius , Wellmann Peter J.
Published: March 2009

In this paper we report, based on analysis of dislocation statistics, on the influence of
growth temperature on the nucleation, propagation and annihilation mechanisms of dislocations.
Using KOH defect etching and optical microscopy we have conducted dislocation tracking along
lengths of crystals grown under various process temperature regimes to study their evolution and
propagation mechanisms statistically. We further present the influence of growth temperature on the
step structure of the growth front using AFM measurements. From the analysis of dislocation statistics
and step structure in relation to temperature we derive the role of surface kinetics of the SiC gas
species on the growth surface in dislocation evolution during PVT growth of bulk SiC.
Migration of Dislocations in 4H-SiC Epilayers during the Ion Implantation Process
Authors: Tsuchida Hidekazu , Kamata Isaho , Nagano Masahiro , Storasta L. , Miyanagi Toshiyuki
Published: March 2009

Synchrotron reflection X-ray topography and KOH etching were applied to investigate the
effects of the ion implantation/annealing process on the existing dislocations in the 4H-SiC epilayers
and second epitaxial growth on the ion implanted layer. No systematic generation of dislocations or
stacking faults caused by the second epitaxial growth on the implanted layer was observed, while
BPDs were confirmed to migrate in the epilayer during the implantation/annealing process. The BPDs
bend markedly near the bottom of the implanted layer and tend to lie along the <1-100>
(perpendicular to the off-cut direction) after the implantation/annealing process. The lattice mismatch
strain created by the implantation is a possible driving force of the glide motion of the BPDs.
Partial Dislocations under Forward Bias in SiC
Authors: Savini G. , El Barbary A.A. , Heggie M.I. , Öberg Sven
Published: March 2009

First-principles calculations are used to investigate the partial dislocations in 4H-SiC. We
have shown that the Peierls barriers are strongly dependent on the dislocation core structures. Our
results have revealed that the asymmetric reconstruction does not possess midgap states while the
symmetric reconstructions, characterized by dangling bond on like atoms along the dislocation line,
are always electrically active. We suggested that under forward bias, the free energies of the
symmetric reconstructions are dynamically lowered by continuous electron-hole transitions between
the respective deep levels and valence/conduction bands.
The DI Defect is Associated with a Stacking Fault?
Authors: Jones Kenneth A. , Zheleva T.S. , Vispute R.D. , Hullavarad Shiva S.
Published: March 2009

Using TEM we show that defective regions are formed in SiC by ion implantation, and
that some of the regions grow at the expense of others. Using HRTEM we show that these regions
contain a large number of stacking faults. It is proposed that these stacking faults are Frank
intrinsic stacking faults formed by condensation of divacancies, and it is this defect that is
associated with the DI defect.
XRD and Photoluminescence Whole-Wafer Mapping of 4H-SiC Wafers
Authors: Ryan Tom , Hennessy John , Harrison Colin , Wang Shou Yin , Webster Gyles , Majima Akihiko
Published: March 2009

The commercial availability of SiC-based devices has been limited by a number of
factors including wafer supply, cost, wafer size and crystal quality. Recently a number of vendors of
4H and 6H SiC wafers have emerged and 100 mm diameter wafers are commercially available. All
vendors now claim to meet or exceed the existing SEMI specifications M55-0304. Both SEMI and
manufacturers’ specifications focus on wafer dimensions and gross physical defects such as micropipes
that are visible by optical inspection. In this paper we describe high-density XRD and PL
mapping measurements on a series of nominally identical, semi-insulating 4H wafers from a range
of manufacturers. We show very large variations in crystal quality, polytypism and
doping/contamination within-wafer, from wafer-to-wafer and vendor-to-vendor. It is logical to
assume that these variations may be responsible for observed variations in device properties and
yield.
XRD Characterization of the 6H-SiC Single Crystal Grown from Si-C-Ti Ternary Solution
Authors: Yashiro Nobuyoshi , Kusunoki Kazuhiko , Kamei Kazuhito , Yauchi Akihiro
Published: March 2009

We carried out the characterization of the crystallinity of the solution growth
self-standing silicon carbide (SiC) crystals, which were grown from Si-C-Ti ternary solution with
Accelerated Crucible Rotation Technique (ACRT). The self-standing crystal exhibited
homogeneous green color without cracks and inclusions. The crystallinity of the self-standing
crystal was characterized by various precise XRD diffraction measurements, such as の-scan rocking
curve measurement, X-ray topography and reciprocal lattice mapping. The Full Width at Half
Maximum (FWHM) of the の-scan rocking curves was about 20 arcsec. The X-ray topography
showed a large area with a homogeneous orientation. The reciprocal lattice mapping exhibited a
sharp single peak indicating the excellent crystallinity. Finally we confirmed rather high
crystallinity of the self-standing crystals by etch pits measurement using molten KOH etching.
Deep Levels in Electron-Irradiated n- and p-type 4H-SiC Investigated by Deep Level Transient Spectroscopy
Authors: Danno Katsunori , Kimoto Tsunenobu
Published: March 2009

The authors have investigated deep levels in electron-irradiated n- and p-type 4H-SiC
epilayers by deep level transient spectroscopy (DLTS). By low-energy electron irradiation at 116 keV,
the Z1/2 and EH6/7 concentrations are increased in n-type samples, and the concentrations are almost
unchanged after annealing at 950°C for 30 min. In p-type samples, the unknown centers, namely EP1
and EP2, are introduced by irradiation. By annealing at 950°C, the unknown centers are annealed out.
The HK4 center (EV + 1.44 eV) is increased by the electron irradiation and subsequent annealing at
950°C. The dependence of increase in the trap concentrations by irradiation (NT) on the electron
fluence reveals that NT for the Z1/2 and EH6/7 centers is in proportional to the 0.7 power of electron
fluence, while the slope of the plot is 0.5 for the HK4 center. The Z1/2 and EH6/7 centers show similar
annealing stage and are thermally stable up to 1500-1600°C, while the HK4 center is annealed out at
about 1350°C. The Z1/2 and EH6/7 centers may be derived from a same origin (single carbon vacancy:
VC) but different charge state. The HK4 center may be a complex including VC.
FTIR Ellipsometry Analysis of the Internal Stress in SiC/Si MEMS
Authors: Pezoldt Joerg , Förster Christian , Cimalla Volker , Will Florentina , Stephan Ralf , Brueckner Klemens , Hein Matthias A. , Ambacher Oliver
Published: March 2009

The resonant frequencies and quality factors of MEMS and NEMS depend critically on
the layer quality and the residual stress in the SiC/Si heterostructure. It is demonstrated, that FTIRellipsometry
is a suitable technique for monitoring the inhomogeneous residual stress inside SiC/Si
heterostructures containing thin layers and their variation with during processing.
Investigation of Charge Carrier Lifetime Temperature-Dependence in 4H-SiC Diodes
Authors: Udal Andres , Velmre Enn
Published: March 2009

Recently published experimental results for 4H–SiC diodes up to 700 °C are used to
deduce the hole lifetime temperature-dependence in n-base for high temperature range. The reverse
recovery measurements are interpreted by the nonisothermal drift-diffusion simulator DYNAMIT.
The uncertainties from lifetimes unknown behavior in emitter layers and consequences from
possible nonuniform lifetime distribution in n-base are analyzed. Results show that up to
temperature 400 °C nearly quadratic dependence of lifetime versus temperature τ ~ T
2 holds. At
higher temperatures lifetime growth is accelerated approximately to quartic dependence τ ~ T
4.
Properties of Different Room-Temperature Photoluminescence Bands in 4H-SiC Substrates Investigated by Mapping Techniques
Authors: Krishnan Bharat , Chanda Sashi Kumar , Koshka Yaroslav
Published: March 2009

The room-temperature photoluminescence (RTPL) was investigated in commercial
nitrogen-doped 4H-SiC substrates. In a typical RTPL spectrum of n-type 4H-SiC substrate, the
‘band-edge’ emission was similar to PL signatures that are typically attributed to free-exciton
recombination in high-quality thick epitaxial layers. The origin of the deep-defect ‘red’ emission
and its influence on recombination properties of SiC remain unclear. In most of the substrates in
which the ‘red’ RTPL band was strong, clear reverse correlation between the ‘red’ and ‘band-edge’
RTPL intensities was observed. In contrast, direct correlation was observed between the ‘bandedge’
PL map and distribution of the net free electron concentration. There is a possibility that
incorporation of nitrogen donors is influenced by (or influences) incorporation of lifetime-limiting
deep defects.
Raman Spectra of a 4H-SiC Epitaxial Layer on Porous and Non-Porous 4H-SiC Substrates
Authors: Clouter Maynard J. , Ke Yue , Devaty Robert P. , Choyke Wolfgang J. , Shishkin Y. , Saddow Stephen E.
Published: March 2009

A lightly doped n-type homo-epitaxial layer was grown by CVD onto a heavily doped n-type
4H-SiC substrate for which half of the surface had been made porous by photoelectrochemical etching.
Raman spectra are obtained in the optic phonon region using three scattering geometries. An effective
medium model for the porous layer is used to assist in the interpretation of the spectra. This work
demonstrates that the contributions to the Raman spectra of the various layers in a sample with multiple
4H-SiC layers can be extracted.
Reverse Biased Electrochemical Etching of SiC-SBD
Authors: Nishikawa Koichi , Maeyama Yusuke , Fukuda Yusuke , Shimizu Masaaki , Sato Masashi , Iwakuro Hiroaki
Published: March 2009

With development of very-low-micropipe-density substrate, reduction of other device
killer defects becomes important for large size power devices. We employed reverse biased
electrochemical etching (RECE) method in order to elucidate where the current leaks out in
Schottky barrier diode. Low concentration 4H-SiC epi-layer with Al implanted guard rings was
electrochemically etched under reverse bias voltage up to 400V in HF-based electrolyte. The
surface of the substrate was observed with Nomarski microscopy before and after RECE. In guard
ring area, holes appeared which are aligned toward off-direction of the substrate. The length of the
aligned holes is about 25μm. The guard ring surrounding the holes were etched uniformly but
limited as though there exists a boundary parallel to the steps. In Schottky contact area, not all but
some of carrot defects showed an etched feature after RECE. Such etching features are also
observed at different position without carrot. We consider that threading screw dislocation is one
cause of leakage current in SBD. An etching feature like tangled strings also appeared. Its outer
dimension is more than 1mm with thickness of about 50μm. The origin of tangled-string-like
feature is not clear yet.
Evaluation of Unintentionally Doped Impurities in Silicon Carbide Substrates Using Neutron Activation Analysis
Authors: Ohshima Takeshi , Tokunaga O. , Issiki Masahiko , Sasajima Fumio , Itoh Hisayoshi
Published: March 2009

Impurity atoms in a high-purity semi-insulating 4H-SiC substrate fabricated by sublimation
and an n-type 3C-SiC substrate fabricated by Chemical Vapor Deposition (CVD) were evaluated by
neutron activation analysis. Cr, Fe, Zn, As, Br, Mo, Sb, Eu, Yb, Hf, Ta, W and Au atoms were
detected in the 4H-SiC fabricated by sublimation. In the 3C-SiC fabricated by CVD, Cr, Zn, As, Br,
Mo, Sb, La Sm and Hf atoms were found. The concentration of these atoms tends to decrease with
increasing atomic number.
New Insight in Scandium-Mediated Growth Techniques: Sc-Related Defects in 4H-SiC and 6H-SiC
Authors: Gerstmann Uwe , Greulich-Weber Siegmund , Rauls E. , Spaeth Johann Martin , Kalabukhova Ekaterina N. , Mokhov E.N. , Mauri Francesco
Published: March 2009

Scandium can be used to influence the stoichiometry of SiC during growth of the hexagonal
polytypes. Using PL-EPR and total energy calculations in the framework of density functional
theory, scandium is predicted to be built in predominantly at the Si-sublattice in form of ScSi
acceptors with acceptor levels at 0.55 eV (6H-SiC) and 0.48 eV (4H-SiC). In addition, new PL-EPR
spectra are found with a large anisotropy in the g-tensor suggesting defect pairs as an origin.
SIMS Investigation of Ge Incorporation in 3C-SiC Layers Grown from Ge-Si Melts
Authors: Peyre Hervé , Habka Nada , Soulière Véronique , Soueidan Maher , Ferro Gabriel , Monteil Yves , Camassel Jean
Published: March 2009

We report the results of a SIMS and micro-Raman investigation performed on cubic (3C)
SiC crystals grown on hexagonal SiC seeds using a Ge-Si bath and the so-called Vapor Liquid Solid
growth technique. From SIMS measurements, we find a Ge concentration which, roughly, scales
like the Ge concentration in the melt and, in term of micro-Raman measurements, explains the
presence of weak but discernable Ge-Ge peaks around 300 cm-1. Since no similar Si-Si vibrations
are found, this discard the possibility of having at the same time both Ge and Si constitutional
super-cooling with two separate Ge and Si phases.
Ab Initio Study of Clean and Hydrogen-Saturated Unreconstructed SiC{0001} Surfaces
Authors: Mattausch Alexander , Dannecker T. , Pankratov Oleg
Published: March 2009

Using density functional theory, we investigate the 6H-SiC{0001} surfaces in the
unreconstructed 1 × 1 and the H-passivated configuration. The strong correlation effects of
the dangling bonds at the surface are treated by spin-polarised calculations including the
Hubbard-U parameter. We find that the clean surfaces are semiconducting with surface states
in good agreement with experimental data. The impact of the Hubbard-U is stronger on the
C-terminated face. For the H-passivated surfaces we find resonances in the valence band. The
antibonding C−H state is located in the upper part of the bandgap around the ¯-point.
Peculiarities of Neutron-Transmutation Phosphorous Doping of SiC Enriched with 30Si Isotope: Electron Paramagnetic Resonance Study
Authors: Ilyin Ivan V. , Muzafarova Marina V. , Baranov P.G. , Ber B.Ya. , Ionov A.N. , Mokhov E.N. , Ivanov Pavel A. , Kaliteevskii M.A. , Kop'ev P.S.
Published: March 2009

High concentration of two types of P donors up to 1017 cm-3 in SiC enriched with 30Si
after neutron transmutation doping (NTD) has been achieved. It was established that annealing at
sufficiently low temperature of 1300oC, that is 500-600°C lower compared with annealing of NTD
SiC with natural isotope composition, gives rise to the EPR signal of shallow P donors, labeled sPc1,
sPc2 and sPh. The correlated changes of the EPR spectra of the three sP centres in all the
experiments and the qualitative similarities with spectra of shallow N donors prove that these
centres have shallow donor levels and a similar electronic structure and belong to different lattice
sites. The annealing at 1700°C results in a transformation of one type of P donors (sPc1, sPc2 and
sPh) into another type having low temperature EPR spectra labeled dP.
Acceleration Factors in Acceleration Life Test of Thermal Oxides on 4H-SiC Wafers
Authors: Senzaki Junji , Shimozato Atsushi , Fukuda Kenji
Published: March 2009

Acceleration factors in acceleration life test of thermal oxides grown on 4H-SiC(0001)
wafers and influences of dislocations on oxide reliability have been investigated using
time-dependent dielectric breakdown measurements. The thermal oxides are formed by dry oxidation
at 1200°C followed by annealing in nitrogen atmosphere. Then, post oxidation annealing in wet
ambient at 950°C or hydrogen atmosphere at 800°C were carried out for some of the oxides.
Aluminum or poly-Si films with thickness of 300 nm were formed as gate electrodes. The
temperature dependence of time-to-breakdown (tBD) indicates that activation energy (Ea) values for
the Al-gate and Poly-Si-gate thermal oxides are 0.59 eV - 0.79 eV and 0.34 eV - 0.72 eV, respectively.
Analyzing the electric field dependence of tBD, it was indicated that the values of electric acceleration
parameters (β) are 2.7 cm/MV - 7.0 cm/MV and 5.8 cm/MV - 7.1 cm/MV for the Al-gate and
poly-Si-gate thermal oxides, respectively. In addition, the charge-to-breakdown decreases with
increase in the density of basal plane dislocation.
Boron Doping during Vapor-Liquid-Solid Growth of Homoepitaxial 4H-SiC Layers
Authors: Soueidan Maher , Ferro Gabriel , Nsouli Bilal , Habka Nada , Soulière Véronique , Younes Ghassan , Zahraman Khaled , Bluet Jean Marie , Monteil Yves
Published: March 2009

Vapor-Liquid-Solid was used for growing boron doped homoepitaxial SiC layers on 4HSiC(
0001) 8°off substrates. Si-based melts were fed by propane (5 sccm) in the temperature range
1450-1500°C. Two main approaches were studied to incorporate boron during growth : 1) adding
elemental B in the initial melt, with two different compositions : Si90B10 and Si27Ge68B5; the growth
was performed at 1500°C; 2) adding B2H6 (1 to 5 sccm) to the gas phase during growth with a melt
composition of Si25Ge75; the growth was performed at 1450°C. In most cases, the growth time was
limited by liquid loss due to wetting on the crucible walls. The longer growth duration (1h) was
obtained when adding B2H6 to the gas phase. In the case of Si90B10 melt, the surface morphology
exhibits large and parallel terraces whereas the step front is more undulated when adding Ge.
Raman and photoluminescence characterizations performed on these layers confirmed the 4H
polytype of the layers in addition to the presence of B which results in a strong B-N donor-acceptor
band. Particle induced γ-ray emission was also used to detect B incorporation inside the grown
layers.
Modification of SiO2/4H-SiC Interface Properties by High-Pressure H2O Vapor Annealing
Authors: Takeda D. , Yano Hiroshi , Hatayama Tomoaki , Uraoka Yukiharu , Fuyuki Takashi
Published: March 2009

We performed high-pressure H2O vapor annealing on 4H-SiC n-MOS capacitors to
control SiO2/4H-SiC interface properties. High-pressure H2O annealing was performed at 270～
420oC at a pressure of 1.31～1.67MPa. Effective negative fixed oxide charge decreased with
increasing anneal temperature in the case annealed with Al gate electrodes. However, it increased
with increasing anneal temperature in the case annealed without Al gate electrodes. The effect of
annealing was much larger on the C-face than that of Si-face. Interface state densities near the
conduction band edge was decreased at 420oC under 1.67MPa compared to other samples,
especially on the C-face n-MOS capacitors.
Optimizing the Thermally Oxidized 4H-SiC MOS Interface for P-Channel Devices
Authors: Das Mrinal K. , Haney Sarah K. , Jonas Charlotte , Zhang Qing Chun Jon , Ryu Sei Hyung
Published: March 2009

Optimization of the thermally oxidized 4H-SiC MOS interface has produced p-channel
lateral MOSFETs with hole inversion layer mobility as high as 10 cm2/Vs. This has been
accomplished by identifying the 1200oC Dry, 950oC Wet (un-nitrided) oxidation as ideal for hole
conduction across the MOS inversion layer and by implant activation annealing at 1800oC of the
heavily implanted n-type well. High temperature measurements show that the high mobility and
normally-off operation is maintained throughout the operating temperature range. Oxide leakage
measurements yield a dielectric strength of 8.5 MV/cm with 90% yield, thereby enabling the
manufacture of high performance p-channel devices like the IGBT.
CVD of 6H-SiC on Non-Basal Quasi Polar Faces
Authors: Shishkin Y. , Rao Shailaja P. , Kordina Olof , Agafonov I. , Maltsev Andrei A. , ul Hassan Jawad , Henry Anne , Moisson Catherine , Saddow Stephen E.
Published: March 2009

Crystal growth of 6H-SiC in two non-basal directions is reported. The two explored
surfaces are the {1-103} plane, named qC-face, and the {1-10-3} plane, named qSi-face. The asgrown
bulk surfaces exhibit a smooth structure with a small ridging effect originating from the
miscut of the seed crystals. Layers, epitaxially grown on the chemically-mechanically polished qCface,
nicely replicate the original crystal structure and show no sign of polytype mixing. Lowtemperature
photoluminescence measurements collected on the epilayers exhibit near bandedge
spectral characteristics indicative of good quality 6H-SiC.
The Schottky Parameter Test for Combined Diffusion Welded and Sputter Large Area Contacts
Authors: Korolkov Oleg , Sleptsuk Natalja , Rang Toomas , Syrkin A. , Dmitriev Vladimir
Published: March 2009

For more authentic comparison of Schottky parameters between combined sputter
(Ti/Ni/Au) and diffusion welded (DW) Al contact and direct DW Al contact to SiC the forward
current-voltage characteristics were measured at the temperature range 293-473 K on full-packed
0.3 cm2 Schottky diodes. Surprising fact was discovered that the temperature behaviour of
parameters remains of the same character for both kind of contacts but for the combined sputter-
DW samples the values of parameters is much closer in magnitude to sputter contacts. Apparently,
chemical treatment before the DW process preserves untouched the contact surface layer formed by
annealing of initial sputter metallization of the chips (e.g. Ni2Si, Ti3SiC2), and this layer serves as
barrier during diffusion welding. In the second part of the work we give the results on long-term
reliability testing where through the SiC Schottky diode with the DW Al contacts during 300 hr has
been passed constant forward stabilized current of 100 A/cm2 density. The primary and final values
of Uf for DW Schottky contact have not changed during the test.
High Throughput SiC Wafer Polishing with Good Surface Morphology
Authors: Kato Tomohisa , Wada Keisuke , Hozomi Eiji , Taniguchi Hiroyoshi , Miura Tomonori , Nishizawa Shin Ichi , Arai Kazuo
Published: March 2009

We report SiC wafer polishing study to achieve high throughput with extremely flat,
smooth and damageless surface. The polishing consists of three process, wafer grinding, lapping
and chemical mechanical polishing (CMP), which are completed in shortest about 200 minutes in
total for 2 inch wafer. Specimens of 4H- and 6H-SiC were provided from slicing single crystal as
wafers oriented (0001) with 0 or 8 degrees offset angle toward to <112
_
0>. By the first grinding
using a diamond whetstone wheel, we realized flat surface on the wafers with small TTV error of 1
μm in 15 minutes. After second process of lapping, the wafers were finished by CMP using
colloidal silica slurry. AFM observation showed not only scratch-free surface but also atomic steps
on the wafers after CMP. Rms marks extremely flat value of 0.08 nm in 10 μm square area.