bluuebunny/crossref_metadata_2025 huggingface dataset:
SiC Migration Enhanced Embedded Epitaxial (ME3) Growth Technology
Authors: Takeuchi Yuuichi , Kataoka Mitsuhiro , Kimoto Tsunenobu , Matsunami Hiroyuki , Malhan Rajesh Kumar
Published: March 2009

In this work, we have developed an innovative epitaxial growth process named the
“Migration Enhanced Embedded Epitaxial” (ME3) growth process. It was found that at elevated
growth temperatures, the epitaxial growth at the bottom of the trenches is greatly enhanced compared
to growth on the sidewalls. This is attributed to the large surface diffusion length of reactant species
mainly due to the higher growth temperature. In addition, it was found that this high temperature ME3
growth process is not influenced by the crystal-orientation. Similar growth behavior was observed for
stripe-trench structures aligned either along the [11-20] or [1-100] directions. No difference was
observed in the electrical performance of the pn diodes fabricated on either oriented stripe geometry.
The ME3 process can also be used as an alternative to ion-implantation technology for selective
doping process.
Relaxation Mechanism of the Defect-Free 3C-SiC Epitaxial Films Grown on Step-Free 4H SiC Mesas
Authors: Du H. , Skowronski Marek , Neudeck Philip G. , Trunek Andrew J. , Spry David J. , Powell J. Anthony
Published: March 2009

Cross-sectional transmission electron microscopy (TEM) was used to investigate the
extended defects in 3C-SiC films deposited on atomically flat 4H-SiC mesas. The nominal layer
thickness was 10 μm and was considerably larger than the critical thickness determined by either the
Matthews and Blakeslee or People and Bean models. Threading dislocation densities determined by
KOH etching are far below densities typical of relaxed heteroepitaxial layers, down to as low as
104cm-2 densities found in 4H-SiC. Misfit dislocations with Burgers vectors of <11 2 0> were
observed in planes parallel to the 3C/4H SiC interface. These defects were interpreted as due to
nucleation of dislocation half loops at mesa edges and glide along the 3C/4H interface.
Structure Evolution of 3C-SiC on Cubic and Hexagonal Substrates
Authors: Yakimova Rositza , Yazdi Gholam Reza , Sritirawisarn Nut , Syväjärvi Mikael
Published: March 2009

We report on growth of 3C-SiC by sublimation process in vacuum with the aim to
ultimately select conditions for single polytype growth of bulk crystals. The 3C polytype
occurrence, growth mechanism and structure evolution have been in the focus of the study. To gain
understanding of the initial formation of the cubic polytype, growth was performed on various
substrates, such as 6H- and 4H-SiC (on-axis and vicinal), as well as freestanding 3C-SiC wafers.
The growth configuration used allowed a high growth rate, e.g. up to 200 (m/h, respectively very
thick layers. The grown material was studied by means of optical microscopy, AFM and HRTEM.
6H-SiC (0001) Si-face substrates may be a good choice if the 3C nucleation is well controlled,
which can be achieved by selecting the initial temperature ramp up and substrate orientation. These
growth conditions limit the number of nucleation centers and decrease the defective boundaries.
Selective Epitaxial Growth of 3C-SiC on Si Using Hexamethyldisilane in a Resistance Heated MOCVD Reactor
Authors: Gupta Aparna , Jacob Chacko
Published: March 2009

Selective epitaxial growth (SEG) of cubic silicon carbide (3C-SiC) was carried out on
patterned Si (100) substrates using SiO2 as a mask. The growth was performed by atmospheric
pressure chemical vapour deposition in a resistance-heated furnace using hexamethyldisilane
(HMDS) as the source. It was observed that voids are the major defect in the case of heteroepitaxial
growth of 3C-SiC on Si. Using selective epitaxial growth, the density of voids was reduced. Lateral
epitaxial overgrowth (LEO) was achieved at selected areas where windows are arrays of stripes.
The effect of temperature, window shape and size, precursor concentration, etc. on the SEG of SiC
has been studied. After growth, films have been characterized by Nomarski optical microscopy,
SEM, Raman spectroscopy and AFM. Faceted growth was observed along (111) planes inside
smaller windows. Raman spectroscopy was used to identify defects and the presence of other
polytypes.
Raman Scattering Analyses of Stacking Faults in 3C-SiC Crystals
Authors: Mitani Takeshi , Nakashima Shinichi , Okumura Hajime , Nagasawa Hiroyuki
Published: March 2009

Visible and deep UV Raman measurements have been applied to investigate the structural
and electrical properties of stacking disordered 3C-SiC crystals. It is found that free-carrier density
shows the significant dependence on the density of stacking faults in 3C-SiC. The density of stacking
faults has been estimated from the comparison between experimentally obtained Raman spectra and
Raman intensity profiles simulated using one-dimensional lattice models considering the disorder in
bond polarizability arrangement.
Silicon Carbide: A Playground for 1D-Modulation Electronics
Authors: Deák Peter , Buruzs Adam , Gali Adam , Frauenheim Thomas , Choyke Wolfgang J.
Published: March 2009

Optoelectronic devices with 1D modulation of the potential through hetero-structure or
doping superlattices have so far been the privilege of III-V semiconductors. Based on the fact that
SiC can be grown monolayer by monolayer, and that Si–Si and C–C double layers have been observed
in it, we suggest the possibility of a stress-free polarization superlattice, consisting of the
periodic variation of Si-face and C-face domains along the hexagonal axis of 4H-SiC. Such a structure
could, in principle, be grown by molecular source atomic layer epitaxy. Investigating such
superlattices by density functional theory, using a hybrid functional, we show that Si–Si and C–C
double layers at the antiphase boundaries confine electrons within ~0.5 nm, and the periodic polarization
field causes zig-zag shaped band edges which gives rise to tunable absorption, to spatial
separation of free electrons and holes, as well as to optical nonlinearity. These properties could
allow the application of SiC also in optoelectronics and photonics.
Examining Dislocations in SiC Epitaxy by Light Emission from Simple Diode Structures
Authors: Liu Kendrick X. , Stahlbush Robert E. , Hobart Karl D. , Sumakeris Joseph J.
Published: March 2009

With a simple processing sequence using only patterned aluminum (Al), dislocations and
stacking faults were examined in thick n- epitaxial layers including a grown p+ layer on top. The
thicknesses of the n- layers were 100 and 150 μm, values that are typical for fabricating 10 kV PiN
diodes. High temperature sintering of the metal film was avoided making this a potentially
nondestructive scheme for evaluating SiC epitaxy. Faulting of basal plane dislocations (BPDs) and
the resulting forward voltage, Vf, increase were examined at current densities up to 20 A/cm2. A
simple guard ring structure defined in the Al pattern was successfully used to confine the current
through the epitaxial layers to the area inside of the ring. Kelvin contacts compensated for voltage
drops at the Al/SiC interfaces. As a result, current-voltage characteristics and electroluminescent
imaging were obtained across a known area of the PiN layer at currents densities ranging from 20
A/cm2 to 7 × 10-3 A/cm2.
Photoemission of 4H-SiC pin-Diodes Epitaxied by the Sublimation Method
Authors: Camara Nicolas , Zekentes Konstantinos , Bano Edwige , Thuaire Aurelie , Lebedev Alexander A.
Published: March 2009

4H-SiC pin diodes were fabricated on epitaxial layers grown by Sandwich Sublimation
Method (SSM). I-V and photoemission measurements were conducted on these devices. These
measurements show hot spots responsible for a soft breakdown and evidence triangular shape
defects previously observed in 4H-SiC pin diodes made on CVD epitaxial layers. These results agree
with the morphology studies which indicate that the SSM-grown layers have a higher number of
structural defects than their counterparts.
Synchrotron X-ray Topographic Analysis of Dislocation Structures in Bulk SiC Single Crystal
Authors: Yamaguchi Satoshi , Nakamura Daisuke , Gunjishima Itaru , Hirose Yoshiharu
Published: March 2009

The detailed properties of the dislocations of SiC crystals were analyzed using
ultrahigh-quality substrates manufactured by RAF (repeated a-face) growth method by means of bulk
X-ray topography. From this analysis, we could reveal the detailed features of one type of basal plane
dislocations and two types of threading dislocations. The basal plane dislocations were screw type
with Burgers vector were parallel to <11-20> direction. One of the threading dislocations was mixed
type close to screw dislocation parallel to the growth direction with Burgers vector of 1c+na (n=0, 1, 2,
…). Another was the edge type parallel to the c-axis, which was lying between two basal plane
dislocations. Moreover, these dislocations were found to be connecting with each other, constituting
large network structures.
Simulation of Threading Edge Dislocation Images in X-Ray Topographs of Silicon Carbide Homo-Epilayers
Authors: Vetter William M. , Tsuchida Hidekazu , Kamata Isaho , Dudley Michael
Published: March 2009

Among the types of dislocation seen in homo-epilayers of SiC grown upon 4H-SiC
wafers with an 8° surface offcut are basal plane dislocations propagated into the epilayer at an 8°
inclination, and threading edge dislocations. These types may be imaged by monochromatic
synchrotron x-ray topography in the grazing-incidence reflection geometry using the 11 2 8
reflection. Equations needed to apply the ray-tracing method of computer simulating x-ray
topographic defect images in this experimental geometry were derived and used to simulate images
of the threading edge dislocations. Simulations of the threading edge dislocations showed 4 μm
wide white ovals with narrow arcs of dark contrast at their ends, inclined relative to the g-vector of
the topograph according to the sign of their Burgers vector. These resembled the experimental
topographs, inasmuch as was possible at the maximum resolution of x-ray topographs.
Non-Equilibrium Carrier Diffusion and Recombination in Semi-Insulating PVT Grown Bulk 6H-SiC Crystals
Authors: Neimontas K. , Kadys Arunas , Aleksiejūnas R. , Jarašiūnas Kęstutis , Chung Gil Yong , Sanchez Edward , Loboda Mark J.
Published: March 2009

We applied a non-degenerate four wave mixing (FWM) technique to investigate carrier
generation, diffusion and recombination processes in PVT-grown semi-insulating wafers of 6H-SiC
at 300 K. The resistivity of samples, cut from different places of a boule as well as from different
boules, varied in range from a few ⋅cm up to 1010 ⋅cm. Interband excitation (at 355 nm) and below
bandgap excitation (at 532 nm) allowed to study dynamics of the bipolar plasma and the contribution
of deep levels to carrier generation and recombination. The nonequilibrium carrier lifetime was
shorter in the samples of higher resistivity, in accordance with the increasing density of deep levels.
The bipolar plasma diffusion in high-resistivity samples (~109 ⋅cm) provided the value of the
diffusion coefficient D = 4.4 cm2/s and hole mobility μh = (88 ± 6) cm2/Vs.
Deep Hole Traps in As-Grown 4H-SiC Epilayers Investigated by Deep Level Transient Spectroscopy
Authors: Danno Katsunori , Kimoto Tsunenobu
Published: March 2009

Deep levels in as-grown p-type 4H-SiC epilayers have been investigated by DLTS. Three
deep hole traps (HK2, HK3 and HK4) can be detected by DLTS in the temperature range from 350K
to 700K. They are energetically located at 0.84 eV (HK2), 1.27 eV (HK3) and 1.44 eV (HK4) above
the valence band edge. The activation energy of the traps does not show any meaningful change
regardless of applied electric field, indicating that the charge state of the deep hole traps may be
neutral after hole emission (donor-like). By the low-energy electron irradiation, the HK3 and HK4
concentrations are significantly increased, suggesting that the origins of the HK3 and HK4 may be
related to carbon displacement. Study on the thermal stability of these hole traps has revealed that the
trap concentrations of HK3 and HK4 are reduced to below the detection limit (1-2 × 1011 cm-3) by
annealing at 1350°C. The HK2 is thermally more stable than HK3 and HK4, and becomes lower than
the detection limit by annealing at 1550°C.
Divacancy and Its Identification: Theory
Authors: Gali Adam , Bockstedte M. , Son Nguyen Tien , Umeda T. , Isoya Junichi , Janzén Erik
Published: March 2009

Only recently the well-resolved hyperfine structure of the P6/P7 EPR center has
been experimentally observed. Based on the calculated hyperfine tensors we assign the P6/P7
center to the high spin state neutral divacancy, which is the ground state in agreement with
the experiment. We propose a mechanism to explain the loss of divacancy signal at high tem-
perature annealing in semi-insulating SiC samples. We discuss the possible correlation between
the divacancy and some photoluminescence centers.
Evidence of the Ground Triplet State of Silicon-Carbon Divacancies (P6, P7 Centers) in 6H SiC: An EPR Study
Authors: Ilyin Ivan V. , Muzafarova Marina V. , Mokhov E.N. , Sankin Vladimir Ilich , Baranov P.G. , Orlinskii S.B. , Schmidt J.
Published: March 2009

P6 and P7 centers, which are responsible for semi-insulating properties of SiC,
were shown to be neutral Si-C divacancies (VSi-VC)o having a triplet ground state. The EPR
experiments that were performed at very low temperatures and in complete darkness exclude
the possibility of a thermal or optically excited triplet state and, as a result, the existing model
of excited triplet state P6 and P7 centers was discarded. The optical alignment process which
induces the spin polarization of the ground triplet 3A state of the P6, P7 centers in SiC was
interpreted to be caused by strong spin selectivity of the intersystem crossing (ISC) nonradiative
transitions from an excited 3E state to a metastable singlet 1A state. The
luminescence and optical absorption are caused by transitions between spin sublevels of 3A
and 3E states. The analogy in properties of a divacancy in SiC and the N-V defect in diamond
allows considering the divacancy in SiC as a potential defect for the single defect
spectroscopy.
Electronic Raman Studies of Shallow Donors in Silicon Carbide
Authors: Püsche Roland , Hundhausen Martin , Ley Lothar , Semmelroth Kurt , Pensl Gerhard , Desperrier Patrick , Wellmann Peter J. , Haller Eugene E. , Ager J.W. , Starke Ulrich
Published: March 2009

We study electronic Raman scattering of phosphorus and nitrogen doped silicon
carbide (SiC) as a function of temperature in the range 7K < T < 300K. We observe a
series of peaks in the Raman spectra which we assign to electronic transitions at nitrogen
and phosphorus donors on different lattice sites. These transitions are identified as valley orbit
transitions of the 1s donor ground state. From the polarization dependence of the observed
peaks, we find that all electronic Raman signals have E2-symmetry of C6v for the hexagonal
polytypes (6H-SiC and 4H-SiC) and E-symmetry of C3v for 15R-SiC. We find a reduction of
the intensities of all valley-orbit Raman signals with increasing temperature and ascribe this
reduction to the decreasing occupation of donor states.
Shallow P Donors in 3C-, 4H- and 6H-SiC
Authors: Isoya Junichi , Katagiri Masayuki , Umeda T. , Son Nguyen Tien , Henry Anne , Gali Adam , Morishita Norio , Ohshima Takeshi , Itoh Hisayoshi , Janzén Erik
Published: March 2009

EPR spectra originating from phosphorus shallow donors occupying silicon sites in 3C-,
4H-, and 6H-SiC are identified by using CVD grown films in which the interference from the signals
from the nitrogen shallow donors is practically absent. Phosphorus donors occupying both silicon and
carbon sites are observed in high-energy phosphorus ion implanted semi-insulating 6H-SiC which
was also free from the interference from the signals from the nitrogen shallow donors.
Donor-Acceptor Pair Luminescence of Phosphorus-Aluminum and Nitrogen-Aluminum Pairs in 4H SiC
Authors: Ivanov Ivan G. , Henry Anne , Janzén Erik
Published: March 2009

The procedure of fitting the spectra associated with donor-acceptor pair luminescence
arising from nitrogen-aluminum and phosphorus-aluminum pairs in 4H SiC is described in detail.
We show that the fitting can be used not only for accurate evaluation of the ionization energies of
the different donors and acceptors involved, but also for unambiguous determination of their lattice
sites.
Conditions and Limitations of Using Low-Temperature Photoluminescence to Determine Residual Nitrogen Levels in Semi-Insulating SiC Substrates
Authors: Glaser E.R. , Shanabrook B.V. , Carlos W.E. , Chung Hun Jae , Nigam Saurav , Polyakov A.Y. , Skowronski Marek
Published: March 2009

We have employed low-temperature photoluminescence to estimate the total residual N
concentration in semi-insulating (SI) SiC substrates where all N shallow donors are compensated in
the dark. The ratio of the nitrogen-bound exciton line (Qo) to the free excitonic emission (I77) as a
function of excitation power density (Pexc) was tracked for several SI 4H-SiC samples with varying
residual N concentration (~ 7x1014 – 5.2x1016 cm-3). Most notably, a linear relationship was found
between Qo/I77 and [N] for [N] < 1x1016 cm-3 while a sub-linear behavior was observed for samples
with higher N levels. This technique should be particularly valuable to map [N] where the levels
are close to or below the present SIMS detection limit of ~ 5-7 x 1014 cm-3. Results obtained for a
limited number of low n-type and SI 6H-SiC substrates are also presented.
Accurate CsM+ SIMS Aluminum Dopant Profiling in SiC
Authors: Smith Howard E. , Tsao Bang Hung , Scofield James D.
Published: March 2009

The accuracy of Secondary Ion Mass Spectrometry (SIMS) depth profiles of aluminum
(Al) dopant in silicon carbide (SiC) has been investigated. The Al SIMS profile differs in shape
depending on whether it was obtained using a cesium (Cs+) or oxygen (O2
+) primary ion beam, and
depends in the former case on which secondary ion is followed. The matrix signals indicate that the
CsAl+ secondary ion yield changes during the Cs+ depth profile, probably because of the work
function lowering due to the previously-implanted Al. These same matrix ion signals are used for a
depth-dependent empirical correction to increase the accuracy of the Al concentration profile. The
physics of these phenomena and the accuracy of the correction are discussed.
SiC Substrate Doping Profiles Using Commercial Optical Scanners
Authors: Caldwell Joshua D. , Glembocki Orest J. , Hansen Darren M. , Chung Gil Yong , Hobart Karl D. , Kub Francis J.
Published: March 2009

Presented is the use of a commercial optical scanner for the mapping of doping density
( ) D N of SiC substrates and as a local probe for D N in different regions. This method provides a
fast and cost effective method for determining D N homogeneity, examining local electrical
characteristics, and recognizing defect sites including areas of different polytypes or
polycrystallinity. Micro-Raman spectroscopy was used to calibrate the transmission intensity with
D N . It is shown that features presented in the calculated D N maps strongly correlate to those
observed in Lehighton resistivity maps.
Columnar Morphology of Porous Silicon Carbide as a Protein-Permeable Membrane for Biosensors and Other Applications
Authors: Rosenbloom A.J. , Nie S. , Ke Yue , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

We present relative recovery data for six proteins diffusing through porous silicon carbide
membranes having a hybrid columnar/dendritic morphology. These membranes are promising
candidates for implantable biosensors. The results are interpreted using an effective medium model.
Impurity Concentration Dependence of Recrystallization Process of Phosphorus Implanted 4H-SiC(11-20)
Authors: Satoh Masataka , Suzuki Tomoyuki
Published: March 2009

The impurity concentration dependence of the recrystallization rate of phosphorus
implanted 4H-SiC(11-20) has been investigated by means of Rutherford backscattering
spectrometry in the annealing temperature range from 660 to 720 oC . The phosphorus ions were
multiply implanted to form the implantation layer with the thickness of 200 nm and the phosphorus
concentration of 1 x 1020, 4 x 1020, or 1 x 1021 /cm3, respectively. The recrystallization rate of the P
ion implantation-induced amorphous layer in 4H-SiC(11-20) increases with an activation energy of
3.4 eV as does the case of the Ar ion implantation-induced amorphous layer in 6H-SiC(11-20) and
(1-100). As the P concentration is increased from 1 x 1020 to 1 x 1021 /cm3, the recrystallization rate
is enhanced from 3.5 to about 5nm/min, while the recrystallization rate for the Ar implantationinduced
amorphous layer was 1.5 nm/min. It is suggested that the recrystallization process is
enhanced by the presence of the substitutional impurity at the amorphous-crystalline interface
during the recrystallization.
Effect of Surface Orientation and Off-Angle on Surface Roughness and Electrical Properties of p-Type Impurity Implanted 4H-SiC Substrate after High Temperature Annealing
Authors: Kinoshita Akimasa , Katou Makoto , Kawasaki Miwa , Kojima Kazutoshi , Fukuda Kenji , Arai Kazuo , Morigasa Fukuyoshi , Endou Tomoyoshi , Isii Takuo , Yashima Teruyuki
Published: March 2009

We investigate the effect of surface orientation and off-angle for Al-implanted 4H-SiC
samples after high temperature annealing. The samples are obtained from a 4H-SiC (0001) substrate
8° off-angled (Si-face 8°off), and (000-1) substrates 8° (C-face 8°off), 4° (C-face 4°off) and less
than 1° off-angled (C-face ~1°off). An n-type epitaxial layer is deposited on all substrates. Multiple
implantations of Al+ (30~200keV) are carried out at 600°C. The total dose is 8.6 × 1015 cm-2. The
Al-implanted samples are annealed in Ar ambient at 1580°C, 1700°C and 1800°C for 30s using the
hybrid super rapid thermal annealing (HS-RTA) equipment.
In this study, sheet resistance (Rs), free carrier concentration (Ns), Hall mobility (μ) and
root-mean square roughness (Rrms) are used to evaluate the Al-implanted samples after high
temperature annealing. Rs for all Al-implanted samples after annealing at 1800°C for 30s is around
18k/. Rrms for the Al-implanted C-face samples after annealing at 1800°C increases with
increasing off-angle. Rrms for the Al-implanted Si-face 8°off sample after annealing increases with
annealing temperature. Rrms for the C-face ~1°off Al-implanted sample after annealing at 1800°C is
lower than that for the Si-face 8°off Al-implanted sample after annealing at 1700°C, moreover Rs
for the C-face ~1°off sample after annealing at 1800°C is about 10% of that for the Si-face 8°off
Al-implanted sample after annealing at 1700°C. It is shown that the C-face ~1°off sample is useful
to fabricate a p+ region with low Rs and low Rrms. If C-face 4H-SiC is used to fabricate devices,
devices made on C-face 4H-SiC with low off angle are expected to decrease any problems caused
by increase of surface roughness after high temperature annealing (~1800°C).
Kick-Out Phenomena in Epitaxially Boron- and Aluminum-Doped 4H-SiC during Implantation and Annealing Processes
Authors: Negoro Yuki , Kimoto Tsunenobu , Matsunami Hiroyuki , Pensl Gerhard
Published: March 2009

It is investigated whether the homogeneous depth profiles of epitaxially doped B or Al
are changed or preserved by implantation of various implanted species and annealing processes. We
have found a strong decrease in the atomic B concentration in epitaxially B-doped layers after
implantation of N+, Al+, and P+ and subsequent annealing at 1700 °C. On the other hand, the Al
profiles in epitaxially Al-doped layers are preserved after the same processes.
Ni Graphite Intercalated Compounds in Ohmic Contact Formation on SiC
Authors: Lu Wei Jie , Michel J.A. , Lukehart C.M. , Collins W.E. , Mitchel W.C.
Published: March 2009

Ohmic contacts on SiC have been investigated extensively in the past decade. However,
the mechanism for ohmic contact formation has been a troublesome issue. The interfacial structures
at the atomic scale responsible for forming ohmic contacts have not been revealed. Our previous
results have shown that carbon can form ohmic contacts on SiC after thermal annealing, and that an
interfacial carbon layer between Ni and the SiC improves the contacts significantly. In this study,
we have investigated the interactions between Ni and carbon, and ohmic contact formation on SiC
using x-ray diffraction (XRD) and Raman spectroscopy. After annealing, ohmic behavior was
observed and Ni graphite intercalated compounds (GICs) were found on Ni/C/SiC structures.
Unlike conventional graphite intercalated compounds, the Ni atoms substitute for carbon atoms in
the graphitic networks in these Ni-GICs. XRD peaks at 21.6° due to the Ni graphitic intercalation
compound (Ni-GIC) and at 26.3° due to graphite have been observed. The distance between
graphitic sheets is 0.403nm in the Ni graphite intercalated compounds, whereas it is ~20% larger in
the graphite. The thickness of the interfacial carbon layer does not affect the formation of Ni-GIC.
Tantalum-Ruthenium Diffusion Barriers for Contacts to SiC
Authors: Wang S.H. , Arnold Owen , Eichfeld C.M. , Mohney S.E. , Adedeji A.V. , Williams John R.
Published: March 2009

Tantalum-ruthenium diffusion barriers for contacts to SiC were investigated in this work.
Stable specific contact resistances of (2 ± 1) x 10-5 Ω cm2 and (4 ± 2) x 10-5 Ω cm2 were measured
on p-type 4H SiC for Al/Ni and Ni ohmic contacts, respectively, when they were beneath Ru-rich
Ta-Ru barriers aged at 350 °C for 3000 h in air. Annealed Ni ohmic contacts on n-SiC aged at
350 °C in air for 1000 h (the longest time tested) are also very stable. Pull tests revealed greatly
improved adhesion between layers in metallization stacks that contained Ta-Ru barriers in place of
previously studied Ta-Ru-N barriers. A 5 nm Ta layer inserted between the Ru-rich Ta-Ru barriers
and Au was found to further improve the adhesion of the metallization stacks.
Si/SiO2 and SiC/SiO2 Interfaces for MOSFETs – Challenges and Advances
Authors: Pantelides Sokrates T. , Wang Sanwu , Franceschetti A. , Buczko Ryszard , Di Ventra M. , Rashkeev Sergey N. , Tsetseris L. , Evans M.H. , Batyrev I.G. , Feldman Leonard C. , Dhar S. , McDonald K. , Weller Robert A. , Schrimpf R.D. , Fleetwood D.M. , Zhou X.J. , Williams John R. , Tin Chin Che , Chung G.Y. , Isaacs-Smith Tamara , Wang S.R. , Pennycook S.J. , Duscher G. , Van Benthem K. , Porter L.M.
Published: March 2009

Silicon has been the semiconductor of choice for microelectronics largely because of the
unique properties of its native oxide (SiO2) and the Si/SiO2 interface. For high-temperature and/or
high-power applications, however, one needs a semiconductor with a wider energy gap and higher
thermal conductivity. Silicon carbide has the right properties and the same native oxide as Si. However,
in the late 1990’s it was found that the SiC/SiO2 interface had high interface trap densities, resulting
in poor electron mobilities. Annealing in hydrogen, which is key to the quality of Si/SiO2
interfaces, proved ineffective. This paper presents a synthesis of theoretical and experimental work
by the authors in the last six years and parallel work in the literature. High-quality SiC/SiO2 interfaces
were achieved by annealing in NO gas and monatomic H. The key elements that lead to highquality
Si/SiO2 interfaces and low-quality SiC/SiO2 interfaces are identified and the role of N and H
treatments is described. More specifically, optimal Si and SiC surfaces for oxidation are identified
and the atomic-scale processes of oxidation and resulting interface defects are described. In the case
of SiC, we conclude that excess carbon at the SiC/SiO2 interface leads to a bonded Si-C-O interlayer
with a mix of fourfold- and threefold-coordinated C and Si atoms. The threefold coordinated atoms
are responsible for the high interface trap density and can be eliminated either by H-passivation or
replacement by N. Residual Si-Si bonds, which are partially passivated by H and N remain the main
limitation. Perspectives for the future for both Si- and SiC-based MOSFETs are discussed.
Effect of Reactive-Ion Etching on Thermal Oxide Properties on 4H-SiC
Authors: Matocha Kevin , Cowen Chris S. , Beaupre Richard , Tucker Jesse B.
Published: March 2009

4H-SiC MOS capacitors were used to characterize the effect of reactive-ion etching of
the SiC surface on the electrical properties of N2O-grown thermal oxides. The oxide breakdown
field reduces from 9.5 MV/cm with wet etching to saturate at 9.0 MV/cm with 30% reactive-ion
over-etching. Additionally, the conduction-band offset barrier height, φB, progressively decreases
from 2.51 eV with wet etching to 2.46 eV with 45% reactive-ion over-etching.
The Influence of Si, Ga and Gd Content on the Magnetic Properties of Pr-Fe-Co-B-Nb HDDR Bonded Magnets
Authors: Galego E. , Takiishi Hidetoshi , de Faria Jr. Rubens Nunes
Published: March 2009

This paper reports the results of investigations carried out to determine the microstructure and magnetic properties of some praseodymium-based magnets represented by the formula Pr14Fe63.9-xCo16B6Nb0.1Mx. Bonded magnets were prepared the annealed alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR) process. The HDDR powders were isostatically pressed and bonded with cyanoacrylate adhesive to form permanent magnets. The effect of addition element content on the magnetic properties of these magnets was investigated. The amount of addition has a significant effect on the magnetic behaviour of these bonded magnets.
The Influence of Al, Cu and P Content on the Magnetic Properties of PrFeCoBNb-Based HDDR Magnets
Authors: Oliveira M.C.L. , Takiishi Hidetoshi , Costa Isolda , de Faria Jr. Rubens Nunes
Published: March 2009

This paper reports the results of investigations carried out to determine the magnetic properties of some praseodymium-based magnets represented by the formula Pr14Fe63.9-xCo16B6Nb0.1Mx. Bonded magnets of various compositions were prepared from annealed alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR) process. The HDDR powders were isostatically pressed and bonded with cyanoacrylate adhesive to form permanent magnets. The effect of the addition element content on the magnetic properties of these magnets was investigated. The amount of Al, Cu and P addition has a significant effect on the magnetic behavior of these magnets. Under the present processing condition 0.3 at%Al enhanced the intrinsic coercivity to 1.27 and a minimal amount of P improved the remanence to 0.77 T. Copper addition was deleterious to the magnetic properties of the HDDR bonded magnets, independently on the content added.
2D Model for Ball Mills
Authors: Campo F. , Escobar Gutiérrez Jairo A.
Published: March 2009

This work develops a mathematical model that explains the ball mills operational speed. The scope of the model is defined by the powder as the number of particles per cm3 and the Relevance defined as the ratio between different forces. In this study, the Relevance is defined as the ratio between superficial tension and inertial forces. The conditions for a free flowing powder and a single particle are differenced and non-dimensional numbers are found. The model proposed use the friction force between mill walls and the powder mass is related by a friction coefficient that can be calculated from angle repose. An experimental approach proves that the suppositions made in order to develop the model were adequate in this way the existence of the non-dimensional numbers is confirmed. It is also discussed the use of non-dimensional numbers to increase processing speeds with by increasing gravity clarifying that a given Relevancy, it is not dependent of the non-dimensional numbers. Thus, the model can help in the design process of ball mills with a deeper understanding of the phenomena.
Influence of the Addition of Rare-Earth Elements on the Sintering of Cemented Carbide
Authors: Gomes C.M.F. , Santos L.C.O. , Silva A.G.P. , Gomes Uilame Umbelino , Holanda J.N.F.
Published: March 2009

This work presents the results of a study concerning the influence of the addition of rareearth
elements (La2O3 and CeO2) on the sintering of the WC/10Co cemented carbide. Several
WC/10Co mixtures containing up to 3 wt.% rare-earth of the cobalt phase were prepared.
Specimens were uniaxially pressed at 200 MPa, and sintered in a vacuum furnace at 1400 °C during
60 minutes. The sintering behaviour was accompanied by the linear shrinkage, density, and
mechanical strength. The development of the microstructure was followed by XRD and SEM. The
results showed that the sintering behaviour of the WC/10Co cemented carbide was influenced by
adding of rare-earth element. In addition, the lanthanium oxide addition was more effective on the
improvement of the physical-mechanical properties of the studied carbide.
Fabrication of Sintered Compact from Aluminum Powder Coated with Tin Deposits by Magnetron DC Sputtering
Authors: Sonoda Tsutomu , Katou Kenji , Jeon Insu , Yamada Yasuo , Asahina Tadashi
Published: March 2009

Fabrication of sintered compact from aluminum powder coated with tin deposits was
examined, in order to enhance the bonding among the aluminum particles under the assistance of tin
and thereby the sintering effect of the aluminum powder, aiming at improving the mechanical
properties of sintered aluminum materials. For the coating of aluminum powder with tin deposits,
the deposition of pure tin onto the aluminum particles was carried out by magnetron DC sputtering
during the self-convective motion of the aluminum powder in a vacuum chamber. The tablet
consisting of the aluminum powder coated with tin deposits was sintered at 650°C in a vacuum
chamber for 2 hours, while the tablet consisting of non-coated aluminum powder was also sintered
under the same condition for comparison. The sintered compact from the coated aluminum powder
was solid and uniform, and its consolidation reached over 95% while that from non-coated
aluminum powder was around 85%. According to tensile tests, the tensile strength of the sintered
compact from the coated aluminum powder was 75.4N/mm2 while that from non-coated aluminum
powder was 71.0N/mm2, and the elongation of the sintered compact from the coated aluminum
powder reached over 20% while that from non-coated aluminum powder was around 10%.
Therefore it was found that the consolidation and the mechanical properties of the sintered compact
consisting of aluminum powder were considerably improved by this powder coating process.
Incorporation of Granite Waste into Vitrified Ceramic Tiles
Authors: Vieira Carlos Maurício Fontes , Monteiro Sérgio Neves
Published: March 2009

The incorporation of a granite waste into a vitrified ceramic tile body was investigated. The granite waste came from an industry of stone sawing operations located in the municipal area of Santo Antônio de Pádua, State of Rio de Janeiro, Brazil. The investigated compositions were elaborated substituting partially and totally the feldspar by the granite waste. Cylindrical specimen were prepared by uniaxial pressure at 30 MPa and then fired at temperatures varying from 1050 to 1200oC. Fired properties such as bulk density, linear shrinkage, water absorption and diametrical compression were determined. The microstructure of fired samples was evaluated by scanning electron microscopy. The results showed that the replacement of feldspar by granite waste promoted a better vitrification, decreasing the open porosity and increasing the mechanical strength.
Brazing of Al2O3 with Rapidly Solidified Melt Spun Ni-Cr-P Alloy Ribbons
Authors: Maciel T.M. , Chang I.T.H. , Strangwood Martin , de Castro Walman Benício
Published: March 2009

Melt spun Ni-Cr-P alloy ribbons were used as filler metal to join Al2O3 substrates together using a vacuum brazing process. The influence of the brazing load, brazing temperature and holding time on the shear resistance of brazed joints was evaluated. The experimental results showed that the holding time was the most important parameter. At a brazing temperature of 1060°C, the shear resistance value increased from 6.17 to 93.7 MPa with increasing brazing time from 20 to 100 min, respectively.
Effect of Isothermal Sintering Time on the Properties of the Ceramic Composite ZrO2-Al2O3
Authors: dos Santos Claudinei , Teixeira L.H.P. , Daguano J.K.M.F. , Strecker Kurt , Elias Carlos Nelson
Published: March 2009

In this work the influence of isothermal sintering time on the microstructural development of ZrO2-Al2O3 composite was studied. Powder mixture of ZrO2 containing 20 wt% Al2O3 was prepared by milling, compaction and sintering at 16000C, in air. The isothermal sintering time at 16000C was varied between 0 and 1440 min. The sintered samples were characterized in terms of phase composition and relative density. Their microstructures were characterized by grain size distributions and average grain size. These results were evaluated using the classic grain growth equation as a function of time, determining the grain growth exponent of these materials. Furthermore, the microstructural aspects were related to the mechanical properties (Vicker’s hardness and fracture toughness) of these composites.
Microstructural Characterization of Equiatomic NiTi Alloy Prepared by High Energy Milling
Authors: Silva Maria do Carmo , Veloso Ana Cris R. , Gomes Rodinei Medeiros , de Lima Severino Jackson Guedes , Melo Tadeu Antonio de Azevedo , Ambrozio Filho Francisco
Published: March 2009

NiTi alloys with equiatomic composition of NiTi have the highest technological
interest for its potencial application in differents areas such as biomedical, naval, aerospace,
nuclear, automobilist , robotic,etc. In this work , it was used a 50Ni50Ti at % powder mixture,
comercially pure, prepared by mechanical alloying in a Attritor with the following conditions:
the milling speed and the ball charge were 1500 rpm and 10:1 respectively. The milling time
was 2,4,8 and 16h, under an argon atmosphere at room temperature. After milling it was
determined the particle size distribution, the phases by X-ray diffractions (XRD) and the
powder morphology by scanning electron microscopy (SEM). The milling promotes
dissolution of Titanium in Nickel and continuous amorphization by increasing the milling
time. After 16h milling the alloy was almost amorphous. The powders after milling were
compacted and heat treated at high temperature and microstructural evolution was
characterized. In the heat treated samples were detected different phases showing
heterogeneity in the alloy. The detected phases were Ni3Ti, NiTi, Ni2Ti and Ni2Ti4O.
Contamination by milling was detected in the powder after milling and in the heat treated
samples.
Study of Calcium Phosphate Deposition on Porous Titanium Samples
Authors: Silva de Medeiros Waléria , de Oliveira Marize Varella , Pereira Luiz Carlos , Cairo Carlos Alberto Alves , Calixto M.A.
Published: March 2009

Surgical implant coatings and grafts for tissue replacement have been made by porous surface materials to improve the implant to bone attachment. In this work, porous titanium samples were produced via powder metallurgy techniques and submitted to the biomimetic process in order to enhance its osteoconductivity. This process allows a nucleation and growth of a calcium phosphate film which makes a chemical bond with titanium. Therefore, it avoids the looseness of this film from substrate. The samples were chemically treated, heat treated at different temperatures and soaked into a modified body fluid solution (mSBF) during periods of 2 and 7 days. Samples with and without pretreatments and not soaked in mSBF were used as controls. SEM and EDX analyses detected a calcium phosphate phase on the sample surfaces treated at 400°C and 600°C and soaked in mSBF for 2 and 7 days. The results demonstrated the potential of the methodology applied for obtaining a bonelike apatite film on porous titanium samples processed by powder metallurgy.
Synthesis of Lanthanum Beta Alumina by the Polymeric Precursor Technique
Authors: Costa G.C.C. da , Muccillo R.
Published: March 2009

Lanthanum beta alumina powders were obtained by the polymeric precursor
technique using lanthanum nitrate, aluminum nitrate, ethylene glycol and citric acid. The
transformations that occur during thermal treatment of the precursor solution were evaluated
by thermogravimetric and differential thermal analysis. Fourier Transform Infrared analysis
for residual carbon qualitative detection and gas adsorption analysis for evaluating specific
surface area, BET method, were carried out in powder specimens heat treated at different
temperatures. High calcination temperature leads to the formation of hard agglomerates. The
powders calcined at 800°C for 4 h have high specific surface area, ~ 120 m2/g. All processed
powders and green pellets sintered at different temperatures were analyzed by X-ray
diffraction for structural phase determination. Single phase LaAl11O18 pellets have application
as solid electrolytes in disposable electrochemical devices for monitoring dissolved oxygen
species in molten steel at very high temperatures, > 1500 °C, during steel production.
Combustion Synthesis as a Preparation Method of Perovskites with Cerium for Metane Oxidation
Authors: Fraga Mariana A. , Pereira R.A. , Greca M. Conceição
Published: March 2009

The aim of this contribution was to evaluate the synthesis of perovskites containing cerium by the combustion synthesis methodology as well as their catalytic behaviour in the methane combustion. Cerium was introduced partially replacing lanthanum into A position of perovskites with general formula AxA’1-xCoO3. The formation of cubic perovskites was confirmed by XRD. The powder containing only lanthanum and strontium in A sites showed a structure transition to orthorhombic at temperatures above 700 °C. The addition of cerium, instead of strontium, induced a structural stabilisation and only a cubic phase was detected up to 1100 °C. High cerium loadings led to the formation of cerium oxide, revealing its up limit into the structure. All samples showed to be active in methane combustion. The results indicated that over the perovskites loaded with cerium the oxygen adsorbed onto the catalyst surface plays a role in the reaction.
Influence of Organoclay on the Physical Properties of Polyethylene Nanocomposites
Authors: Araújo Edcleide Maria , Oliveira Amanda D. de , Barbosa Renata , de Mélo Tomás Jefférson Alves
Published: March 2009

In this work, polyethylene/montmorillonite clay nanocomposites were
produced by melt intercalation. The clays were treated with quaternary ammonium salts
and then treated and untreated clays were introduced in polyethylene. The clays were
characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared
Spectroscopy (FT-IR). The nanocomposites were characterized by mechanical and
flammability properties. The results showed that the mechanical properties were
improved by introduction of organoclay in polyethylene matrix. By adding only 3wt%
montmorillonite, the burning rate of the nanocomposites was reduced by 17% in
relation to PE matrix.
Study of Corrosion Resistance of Sintered Fe-2%Ni, Fe-5%Ni and Fe 10%Ni with Electroactive Polymeric Coating of Poly trans-[RuCl2(vpy)4]
Authors: Sobral A.V.C. , Franco César V.
Published: March 2009

The use of generated coated polymeric films by electrochemistry means in the sintered
metallic surfaces has been being the focus of our research aimed at the corrosion protection of
small mechanical components obtained from powder metallurgy. The sintered alloys Fe-
2%Ni, Fe-5%Ni and 10%Ni with polymeric coating were tested using electrochemistry
methods in corrosive solutions of NaCl 3%, KNO3 1.25M, H2SO4 0.5M, HNO3 0.5M, acetic
acid 1%, oxalic acid 1% and lactic acid 1%. The electrochemistry corrosion tests were
performed using two techniques, Eocp vs. Time and Potentiodynamic and they proved the
efficiency of the polymeric coating on the corrosion protection of sintered alloys.
Real-Time Dispatch Strategy for Products Manufacture Based on Singular and Lattice Order Rough Set Theory
Authors: Su Hong Sheng , Dang Jian Wu , Li Qun Zhan
Published: March 2009

Under market surroundings, the demands of market to products are dynamic. The primary static production pattern is difficult to suit it well because of larger lag time. To change the situation and optimize resources allocation, based on singular and lattice order rough set of their dynamic characteristics and knowledge discovery abilities, in this paper we present a novel modeling method for products dispatch procedure under dynamic environment. Some unexpected events such as urgent processing and market demands alteration are also fully considered, reselection and rescheduling of the products inside real-time window are also studied. Rough model of real-time dispatch for the products is established based on single rough set. Then the products within the scope of real-time window are ranked in light of their manufacture priorities based on lattice rough set. In the end, a simulation trial indicates the proposed method can better adapt to dynamic indeterminate environment and reduce the scale of solution, and is an effective real-time dispatch strategy.
Research and Application in Supply Chain Management Based on Correlation Analyze of Association Rules Algorithm
Authors: Qu Shou Ning , Wang Qin , Liu Kui , Xu De Jun
Published: March 2009

In this paper, the association rule algorithm and its defects were analyzed. An improved
algorithm was put forward for applying it to analysis the association of products fittings in SCM.
The application of improved algorithm can mine which kinds of fittings or sets of items being
matched to get a salable product or gain the higher profit. So it can not only instruct customer’s
consumption but also can help the entrepreneur make a detailed and efficient internal plan.
Green, Flexible, Intelligent: Clamping System Based on Thermal Sensitive Material with Volume Effect
Authors: Wang Ming , Zhong Kang Min , Zuo Dun Wen , Wang Min
Published: March 2009

Nowadays, the research on the greenization of clamping technology obviously lags the
research of green cutting, green machine tool etc. This paper provides a new clamping system to
clamp the workpiece by the green fast heating/cooling adverse-change semiconductor technology
and temperature controllability to thermal sensitive medium with volume effect. This clamping
system has a low speed operating part, few moving parts, low medium leakage and noise pollution
and it is convenient to be flexible configuration of multi-place, multi-workpiece and multi-direction
clamping. Furthermore, the clamping system can use the sensors of temperature, pressure and
displacement to collect the relative data and process them by computer, then intelligently control the
clamp force and clamping displacement.
An Intelligent Cutting Database for Die and Mold Making Operations
Authors: Liu Zhan Qiang , Xiang Ke Jun , Peng Xiu Guang
Published: March 2009

In the modern manufacturing of sophisticated parts with 3D sculptured surfaces, die/mold
making operations are the most widely used machining processes to remove unwanted material. To
manufacture a die or a mold, many different cutting tools are involved, from hole-drills to the smallest
ball nose end mills. Since the specification of each tool is very different from each other, each
die/mold is specific with their complicated shapes and many machining rules exist to consider, a great
deal of expertise is needed in selecting cutting tools for the die/mold machining operations. An
intelligent system developed by using case-based reasoning (CBR) technology for this purpose is
described in the present work. The geometry of the workpiece, workpiece condition, and operation
type are considered as input values and various recommendations about the tool material, tool type,
tool specifications, and cutting parameters are provided.