bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Properties and Stability of Metastable Phases in the Zr-Nb System
Authors: Aurelio G. , Fernández Guillermet A. , Cuello G.J. , Bozzano P.B.
Published: March 2009

The lattice parameters of the bcc (b) and omega (W) phases occurring metastably in a series of Zr-rich Zr-Nb alloys have been determined at and above room temperature (TR) using neutron diffraction techniques. In the first place, the effect of temperature changes upon the lattice parameters of the b and W phases in alloys with 10 and 18 at.% Nb was monitored using neutron thermodiffraction. A method of analysis is applied to the data which involves a confrontation between the observed structural properties and an idealised -or ``reference'- behaviour (RB) which admits a simple mathematical description. A generalised form of Vegard's law is adopted as RB for the b phase, whereas a specific RB is proposed for the W structure. The experimental data are well accounted for by this interpretation scheme, leading to a picture of the isothermal reactions occurring at high temperature which involves the transfer of Nb from the W to the b phase. Finally, the neutron diffraction data on the W phase are combined with an electron microscopy study for the alloy with 10 at.% Nb aged at 773 K, which provides information on the composition of this phase and its evolution towards thermodynamic equilibrium.
Thermal Conductivity and Acoustic Performance of Volcanic Pumice Based Composites
Authors: Hossain K.M.A. , Lachemi M.
Published: March 2009

Volcanic Pumice (VP) is found abundantly in various parts of the world. In this study, VP from East New Britain province of Papua New Guinea is investigated and assessed for its industrial utilization. The manufacturing of heat-insulating lightweight concrete, building blocks or composites using VP is of prime importance as an energy saver. The utilization of VP as a heatinsulating material is tested and the results are found to satisfy the ASTM requirements. This fact suggests that VP could be utilized in the manufacture of composite building blocks or concrete.
Acoustic performance of composite building floors with lightweight volcanic pumice concrete (VPC) is also described based on the performance of normal concrete (NC) and Code based requirements. The performance of VPC and NC composite floors is judged based on Sound Transmission Class (STC) or Impact Insulation Class (IIC) values. VPC composite floors exhibit better acoustic performance than their NC counterparts and seem to achieve the requirements of Codes of various countries.
Ductile-Brittle Behavior of Microcracks in 3D
Authors: Pelikán V. , Hora Petr , Machová Anna , Landa Michal
Published: March 2009

Results of several parallel molecular dynamics crack simulations in bcc iron crystals with up to 128 million atoms are presented. The crack (001)[010] of Griffith type is loaded in Mode I. We observe dislocation emission and twinning near the free sample surfaces and later plastically induced crack initiation.
A Three Dimensional Discrete Dislocation Dynamics Analysis of Cyclic Straining in 316L Stainless Steel
Authors: Déprés Christophe , Robertson Christian F. , Fivel Marc , Degallaix Suzanne
Published: March 2009

The early stages of the formation of dislocation microstructures in low strain fatigue are analysed,using three-dimensional discrete dislocation dynamics modelling (DDD). A detailed analysis of the simulated microstructures provide a detailed scheme for the persistent slip band formation, emphasizing the crucial role of cross-slip for both the initial strain spreading inside of the grain and for the subsequent strain localization in the form of slip bands. A new ad-hoc posttreatment tool evaluates the surface roughness as the cycles proceed. Slip markings and their
evolutions are analysed, in relation to the dislocation microstructure. This dislocation-based study emphasizes the separate contribution of plastic slip in damage nucleation. A simple 1D dislocation based model for work-hardening in crystal plasticity is proposed. In this model, the forest dislocations are responsible for friction stress (isotropic work-hardening), while dislocation pile-ups
and dislocation trapped in Persistent Slip Bands (PSB) produce the back stress (kinematic workhardening). The model is consistent with the stress-strain curves obtained in DDD. It is also consistent with the stress-strain curves experimentally obtained for larger imposed strain amplitudes.
Dislocation Structures of Duplex Stainless Steel in Uniaxial and Biaxial Cyclic Loading
Authors: Petrenec Martin , Aubin Veronique , Polák Jaroslav , Degallaix Suzanne
Published: March 2009

Austenitic-ferritic duplex stainless steel has been subjected to uniaxial and biaxial nonproportional cyclic loading with the same equivalent strain amplitude. The dislocation structures in specimens fatigued to fracture using both types of loadings were studied and compared. Uniaxial cyclic loading, both in austenitic and in ferritic grains, produces simple structures due to activation of predominantly one slip system. Non-proportional cyclic loading results in formation of cell and wall structures and thus in higher stress response of the material.
Influence of Lattice Anisotropy on Models Formulated by Cellular Automata in Presence of Grain Boundary Movement: A Case Study
Authors: Kroc Jiří
Published: March 2009

This paper continues in the previous research focussed to two simple questions.
The first one reads: ”What is the influence of anisotropy of computational lattice on
simulations of boundary movement” where grain boundary movement typically appears in simulations of grain boundary migration and static/dynamic recrystallization. The second question reads: ”How is the computational anisotropy related to natural anisotropy of the material lattice itself” This study is focussed on the influence of change of the computational algorithm and/or lattice on the grain boundary movement. Two algorithms, the majority rule and the simple modification of the Monte Carlo method for two different lattices – namely square and hexagonal one – are used.
Local and Global Fracture Properties in Metal Matrix Composites
Authors: Sabirov I. , Kolednik Otmar
Published: March 2009

The relation between the local and global values of the fracture initiation toughness is
investigated for a cast Al6061-based metal matrix composite with 10% of Al2O3 particles after different heat treatments. The global values of the fracture initiation toughness are determined by conventional fracture mechanics tests. The local values of the fracture initiation toughness are found by measuring the critical crack tip opening displacement (CODi) at different locations along the crack front. To do this, an automatic fracture surface analysis system is applied. Despite of the large scatter of the individual CODi-values, a good correlation to the global fracture initiation toughness values is found.
3D Visualisation of Short Crack Propagation in Al Alloy Using High Resolution Synchrotron X-Ray Microtomography
Authors: Ferrié Emilie , Buffière Jean Yves , Ludwig Wolfgang
Published: March 2009

In-situ fatigue tests monitored by Synchrotron Radiation X-ray microtomography were carried out in order to visualize the three dimensional (3D) shape and evolution of short cracks in the bulk of a cast Al alloy. After the in-situ fatigue test the sample has been infiltrated with liquid Gallium (Ga) in order to visualize the grain structure of the material. Irregularities of the crack advance along the crack front can clearly be correlated to the grain structure of the material.
Grain Size Estimation in Anisotropic Materials
Authors: Saxl Ivan , Ponížil Petr , Sülleiová Katarína
Published: March 2009

The estimators proportional to (NA(x,y)NA(x,z)NA(y,z))1/2 and (NL(x)NL(y)NL(z)) obtained by profile and intercept counts are recommended by ASTM Standards E 112 for 3D grain intensity l of anisotropic grain structures (NA(•) are estimated in three mutually perpendicular planes suitably
oriented with respect to the prevailing anisotropy direction and NL(•) are intercept intensities along three suitably selected mutually perpendicular directions). However, l is also related to the profile and intercept intensities l', l', namely l= c'(l')3/2= c'(l')3. The induced intensities are estimated by
arithmetic means NA = (NA(x,y)+NA(x,z)+NA(y,z))/3, NL = (NL(x)+NL(y)+NL(z))/3. A simple model isdeveloped, in which the role of geometric and arithmetic means of profile and intercept counts in the grain size estimation is elucidated. Its results are compared with computer simulated random tessellations with prevailing rod-like and plate-like cells and applied to anisotropic grain structures
of pure Al produced by ECAP and to platinum based composite Pt - 0.5 Y2O3.
Biocompatibility of Carbon Layer on Polymer
Authors: Kubová O. , Bačáková Lucie , Švorčík Václav
Published: March 2009

Polymers with modified surface structure are useful for medicine applications. This study is focused on the surface properties of polymers with carbon layers and their biocompatibility. For experiments was used polyethyleneterephtalate (PET). We used magnetron sputtering for producing of the carbon layers. Raman spectroscopy, goniometry, AFM – microscopy, X-ray diffraction and infrared spectroscopy were used in our experiments to describe the physicochemical properties of modified polymers. Biocompatibility of structure polymer-carbon layers was studied with method in vitro. We investigated adhesion of mouse 3T3-fibroblasts. The carbon layers have positive influence on biocompatibility.
Biocompatibility of Polyethylene Doped with Oxycellulose
Authors: Mikulíková Regina , Kolářová Kateřina , Bačáková Lucie , Švorčík Václav
Published: March 2009

Physical and chemical properties of polyethylene (PE) films doped with calcium salt of oxycellulose (Ca-oxy) and its interaction with cells in culture conditions were studied. The samples with various concentrations of Ca-oxy (0-20 %) were prepared. Samples were tested by goniometer measurements, X-ray diffraction, FTIR spectroscopy and SEM. Sample weight changes during boil sterilization and adhesion and proliferation of tissue cells (3T3 mouse fibroblasts) were studied. It
was found that wetting angle of the doped films decreased with increasing Ca-oxy concentration to up to 10% and then increased again. Both film surfaces had different amount of crystalline phase, thereby different surface roughness. Due to a smaller surface roughness, cell growth was much better on the inner surface of the film than on the outer one. Cells adhered better to samples with 1% of Ca-oxy and with a higher content of oxycellulose over 7%. Cell proliferation was the best on
samples with 1-5% Ca-oxy. Samples were polished to modify their surface roughness. Polishing increased cell proliferation especially on samples with a lower Ca-oxy concentration (1-5%).
Strain Heterogeneity and Damage Localization in Nodular Cast Iron Microstructures
Authors: Nicoletto Gianni , Collini Luca , Konečná Radomila , Bujnová P.
Published: March 2009

Fracture mechanisms of ferritic/pearlitic nodular cast iron are influenced by the
heterogeneous matrix microstructure. This contribution is aimed at understanding the role of a heterogeneous matrix on the localization of damage due to mechanical loading. Therefore, bend specimens made of different nodular cast iron were plastically deformed and the degree of strain heterogeneity determined by comparison with a homogenized response. To address these observations elastic-plastic finite element models of local microstructures were developed. Computed strain maps are examined to understand the link between microstructural features and conditions for damage localization.
Effect of Structure on Creep Behaviour of Superalloy Single Crystals
Authors: Lukáš Petr , Kunz Ludvík , Svoboda Milan , Čadek J.
Published: March 2009

Creep behaviour of two types of superalloy single crystals of the orientation <001> was studied at 850 °C in air to assess their relative suitability for turbine blade applications: CMSX-4 and its potential low cost alternative, CM186LC. The chemical composition of these two superalloys is similar, their microstructure, especially g/g’ distribution, differs substantially. At the same applied stress, the time to failure of CM186LC is shorter than that of CMSX-4. Simultaneously, the creep rate of CM186LC is higher than that of CMSX-4 for the whole lifetime. This is attributed to easier activation of dislocation sources within large g’particles present in
CM186LC crystals.
Damage Mechanisms and Rupture Criterion of PM Ti-6Al-4V at 20K
Authors: Di Iorio S. , Briottet L. , Rauch Edgar F. , Guichard Didier
Published: March 2009

A two parameters rupture criterion for Ti-6Al-4V is proposed, based on cryogenic rupture tests. microstructural observations and FEM analysis,. The damage mechanisms including the cavities nucleation process are analyzed. Moreover, the final steps of rupture are discussed with the help of the thermo-mechanical coupling mechanisms that are expected to operate at low temperatures.
Finite Element Computational Technology in Resonant Ultrasound Spectroscopy of Composite Materials
Authors: Kolman Radek , Plešek Jiří , Landa Michal
Published: March 2009

RUS−resonant ultrasound spectroscopy is a recent experimental−numerical method for the determination of moduli of elastic materials. Generally, all 21 elastic components of the elastic tensor can be determined by the numerical procedure based on the knowledge of a mechanical spectrum of a specimen. This involves the solution of a demanding inverse problem. Currently, the RUS technology allows the determination of material parameters of composite materials consisting of several layers with different material properties. In the present work, the fixed point iteration
method in connection with the finite element method developed earlier is extended to optimize elastic moduli of layered materials. Properties of the fixed point iteration method are tested on a bicrystal specimen.
Investigation of Dynamic Strain Ageing Effects of Low Alloy Steels 15Kh2MFA and 15Kh2NMFA
Authors: Ernestová Miroslava
Published: March 2009

The paper summarizes results of tensile tests in low alloy steel (LAS) specimens (steels 15Kh2MFA and 15Kh2NMFA). Slow Strain Rate Tensile tests (SSRT) were performed in air at temperatures from 22 to 325°C over a wide range of strain rates from 2.5×10-6 to 1.67×10-3 s-1. The possible effect of strain rate and temperature to mechanical properties of tested LAS is searched for.
The dynamic strain ageing (DSA) was observed within certain temperature ranges at lower strain rates tested and its hardening effect in terms of the maximum strengthening stress decreased linearly with the increase of log strain rate. It has been found that the occurrence of susceptibility to environmentally assisted cracking (EAC) of tested steels in high temperature water (HTW) is corelated
to the DSA behavior. The result suggest that DSA reduces ductility of reactor pressure vessel (RPV) steel and its role in enhancing the EAC of RPV steels should not be neglected, in view of the coincidence with susceptibility zones for DSA and EAC in terms of strain rate and temperature. A reasonable coincidence was observed between the susceptibility to DSA exhibited by SSRT in air and with the EAC behavior observed in laboratory experiments.
Influence of Surface Skin on the Fatigue Properties of Die-Cast Magnesium Alloy AS21X
Authors: Lamark T.T. , Janeček Miloš , Estrin Yuri
Published: March 2009

The influence of the surface condition and elevated temperature on the fatigue properties of high pressure die cast magnesium alloy AS21X was investigated. Separately cast specimens were tested under tensile cyclic loading, at room temperature and 150°C. With the as-cast surface layer intact, no significant temperature influence on fatigue life was found for large stress amplitudes, whereas
the fatigue strength at 107 cycles was found to drop from 50 MPa at 20°C to 40 MPa at 150°C. Fracture surface analysis revealed that the predominant fatigue cracks originated from pre-existing surface defects.
Electrical Properties of Polymer Composites
Authors: Podgrabinski T. , Slepička Petr , Rybka V. , Švorčík Václav
Published: March 2009

Permittivity of about 1 µm thin films prepared from polymethylmetactrylate (PMMA)
solution doped with 20 % of diphenyl sulfoxide was studied. Permittivity of the films was measured as a function of the temperature. The measurement of the dependence of polarization on electrical field was performed using a standard Sawyer-Tower circuit. The presence of the dopant increases the composite permittivity namely above the PMMA glass transition temperature. Hysteresis loops
observed on the measured polarization vs. electrical field dependence indicate easier and more pronounced polarizability of the composite comparing to pristine PMMA.
Application of Giant Magnetostrictive Material into Construction of Broad Spectrum Vibration Generator
Authors: Bomba Jacek , Kaleta Jerzy , Sawa Paweł
Published: March 2009

The paper presents an application of giant magnetostriction phenomenon into
particular vibration generator. It was assumed that the generator should enable tests of construction under local loads applied with broad spectrum of frequencies. Mass of a device must be minimal, it should exert large forces with large amplitudes and high efficiency. The applied material is Terfenol-D - an alloy of rare earth elements and iron which exhibits giant magnetostriction. It is a compound of Laves phases with cubic MgCu2 structure. Examinations ofmagnetomechanical properties of Terfenol preceded construction. The efficiency of transformation of magnetic energy into the mechanical one was tested. The key role in efficiency is played by initial compressing prestresses involved and stimulation by constant magnetic field.
The output quantities of constructed device as force, displacement and frequency are completely controlled. The control system includes modern power DC amplifier. It was shown some experimental results of examination of the magnetostrictive actuator. Examples of generations of mechanical vibrations in various constructions enter the new area of applications of Smart Magnetic Materials.
Experimental Identification of Magnetorheological Composites and Elastomers Properties
Authors: Kaleta Jerzy , Lewandowski Daniel , Zając Piotr
Published: March 2009

The paper presents measurement and results of mathematical modelling of damping in cyclic loaded magnetorheological composites - MRC. The original experimental set-up for cyclic shearing mode has been created. Examples of possible applications, measurement and processing mechanical signals (shear stress - T, deformation - g) and magnetic signals (strength of magnetic field - H) were
provided. For the modelling four-parameters viscoelastic-viscoplastic model was chosen. Result of identification confirmed an appropriate choice of the model.
A 3.5 kV Thyristor in 4H-SiC with a JTE Periphery
Authors: Brosselard Pierre , Bouchet Thierry , Planson Dominique , Scharnholz Sigo , Pâques Gontran , Lazar Mihai , Raynaud Christophe , Chante Jean-Pierre , Spahn Emil
Published: March 2009

Overcoming the physical limits of silicon, silicon carbide shows a high potential for
making high voltage thyristors. After a simulation based optimization of the main thyristor parameters, including JTE protection and a SiO2 layer passivation, 4H-SiC GTO thyristors were realized and characterized. Designed for a theoretical blocking capability of nearly 6 kV, the electrical characterization of all device structures revealed a maximum blocking voltage of 3.5 kV. Comparing simulation and measurement suggests that a negative oxide charge density of ~ 2×1012 cm-2 causes the decrease in electrical strength.
High Temperature Hydrocarbon Sensing with Pt-Thin Ga2O3-SiC Diodes
Authors: Trinchi A. , Wlodarski W. , Faglia G. , Ponzoni A. , Comini E. , Sberveglieri G.
Published: March 2009

Silicon carbide based metal-oxide-semiconductor (MOS) devices are attractive for gas sensing in harsh, high temperature environments. We present a hydrocarbon gas sensor based on a Pt–thin Ga2O3–SiC device. This sensor has been employed as a Schottky diode, and is capable of operating at temperatures around 600°C. Exposure to propene (C3H6) gas results in shift towards
lower voltages in the current-voltage (I-V) characteristic curve, as well as a change in series resistance of the diode. The Ga2O3 thin films were prepared by the sol-gel process and deposited onto the SiC by spin coating. The Pt layer was deposited on the top of the Ga2O3, forming the Schottky contact. It also serves to dehydrogenate the hydrocarbons. The sensors responses were stable and repeatable towards propene at operating temperatures between 300 and 600°C. In this paper the effect of biasing is investigated by analyzing the output voltage of the diodes when biased at different constant currents.
Experimental Investigation and Simulation of Silicon Droplets Formation during SiC CVD Epitaxial Growth
Authors: Melnychuck Galyna , Koshka Yaroslav , Mazzola Michael S. , Wyatt Jeffery L.
Published: March 2009

Mechanisms and consequences of silicon vapor condensation during SiC epitaxial
growth or implant annealing with silane overpressure were investigated. The model for the silicon liquid droplets formation in the gas phase and their deposition on the surface of the SiC substrate was developed. The droplet formation dependence on the silane flow rate, temperature profile in the reactor, and the local temperature variations introduced by the wafer carrier and SiC substrate were investigated.
CVD Growth and Characterization of 4H-SiC Epitaxial Film on (11-20) As-Cut Substrates
Authors: Zhang Ze Hong , Gao Ying , Arjunan Arul , Toupitsyn Eugene , Sadagopan Priyamvada , Kennedy Robert M. , Sudarshan Tangali S.
Published: March 2009

Thick epilayers up to 60 µm have been grown on ) 0 2 11 ( face SiC substrates at a growth rate of 15 µm/hr by chemical vapor deposition (CVD). The epilayer surface is extremely smooth with a RMS roughness of 0.6 nm for a 20µm×20µm area. Threading screw and edge dislocations parallel to the c-axis are present in the ) 0 2 11 ( substrate; however, they do not propagate into the epilayer. The I-V characteristics of the Schottky diodes on this face were studied. Basal plane (0001) dislocations with a density of ~105 cm-2 were found in the ) 0 2 11 ( epilayers by molten KOH etching and electron beam induced current (EBIC) mode of the scanning electron microscope (SEM).
Epitaxial Overgrowth of 4H-SiC for Devices with p-Buried Floating Junction Structure
Authors: Nishio Johji , Ota Chiharu , Shinohe Takashi , Kojima Kazutoshi , Okumura Hajime
Published: March 2009

The epitaxial overgrowth process was examined with a view to realizing the
p-buried floating junction structure. The growth condition was investigated to reduce the p-type impurity contamination and to minimize the auto-doping. Total p-type impurity concentration was reduced to 1/50 of the n-type carrier concentration of the drift layers. The buried p-type floating structure was realized for the first time, using 4H-SiC material.
Reduction of Stacking Faults in Fast Epitaxial Growth of 4H-SiC and its Impacts on High-Voltage Schottky Diodes
Authors: Fujiwara H. , Kimoto Tsunenobu , Tojo T. , Matsunami Hiroyuki
Published: March 2009

Generation of stacking faults (SFs) in fast epitaxial growth of 4H-SiC(0001) has been reduced in vertical hot-wall chemical vapor deposition (CVD). 52 µm-thick epilayers with and without SFs are used to investigate impacts of SFs on the performance of Schottky barrier diodes (SBDs). The density, shape and structure of stacking faults have been characterized by cathodeluminescence (CL), photoluminescence (PL) and high-resolution transmission electron
microscopy (HR-TEM). These analyses indicate that most (> 75 %) SFs with an 8H structure are generated near the epilayer/substrate interface during CVD. It is also revealed that the SFs cause the lowering of Schottky barrier height as well as the decrease of breakdown voltage.
Computer Simulation of the Early Stages of Nano Scale SiC Growth on Si
Authors: Safonov K.L. , Trushin Yuri V. , Ambacher Oliver , Pezoldt Joerg
Published: March 2009

Solid source molecular beam epitaxy was applied to create silicon carbide nanoclusters on silicon. The island size distribution can be controlled by an appropriate substrate temperature, carbon fluxes and process times. Rate equation computer simulation was applied to simulate the experimental obtained nano scale nuclei properties.
Growth of 3C-(Si1-xC1-y)Gex+y Layers on 4H-SiC by Molecular Beam Epitaxy
Authors: Weih Petia , Romanus Henry , Stauden Thomas , Spieß Lothar , Ambacher Oliver , Pezoldt Joerg
Published: March 2009

In the present work cubic 3C-(Si1-xC1-y)Gex+y solid solutions were grown at different^temperatures by molecular beam epitaxy on on-axis 4H-SiC (0001) substrates. Two different growth methods are compared in order to explore the optimal growth conditions for the incorporation of Ge into the SiC lattice during the low temperature epitaxy. For this reason simultaneous growth and migration enhanced epitaxy were used. The chemical composition of the
grown layers were analyzed by energy dispersive x-ray methods during transmission electron microscopy investigations. It was found that the migration enhanced epitaxy is a more suitable technique for the formation of high quality (Si1-xC1-y)Gex+y solid solutions. Additionally, polytypes transition from 4H-SiC to 3C-SiC occurs during the growth independent of the applied growth technique.
Regrowth of 3C-SiC on CMP Treated 3C-SiC/Si Epitaxial Layers
Authors: Mank Hugues , Moisson Catherine , Turover Daniel , Twigg Mark E. , Saddow Stephen E.
Published: March 2009

In this work, we have investigated the 3C-SiC re-growth on planarized 3C-SiC epitaxial layers, grown on (001)Si, after the application of a chemical mechanical polishing (CMP) process. A specific polishing process was developed for 3C-SiC to achieve a flat, high-quality surface. The interface between the deposited 3C-SiC and the polished 3C-SiC on Si film was studied by TEM characterization to determine if defects appear at this interface. It was observed that no additional
defects were nucleated at the interface. The resulting re-grown film roughness, as a function of film thickness, was studied and is reported along with recommendations for future work.
Low Temperature Chemical Vapor Deposition of 3C-SiC on Si Substrates
Authors: Förster Christian , Cimalla Volker , Ambacher Oliver , Pezoldt Joerg
Published: March 2009

In the present work an UHVCVD method was developed which allows the epitaxial
growth of 3C-SiC on Si substrates at temperatures below 1000°C. The developed method enable the growth of low stress or nearly stress free single crystalline 3C-SiC layers on Si. The influence of hydrogen on the growth process are be discussed. The structural properties of the 3C-SiC(100) layers
were studied with reflection high-energy diffraction, atomic force microscopy, X-ray diffraction and the layer thickness were measured by reflectometry as well as visible ellipsometry. The tensile strain reduction at optimized growth temperature, Si/C ratio in the gas phase and deposition rate are demonstrated by the observation of freestanding SiC cantilevers.
Challenge to 200 mm 3C-SiC Wafers Using SOI
Authors: Nakao Motoi , Iikawa Hirofumi , Izumi Katsutoshi , Yokoyama Takashi , Kobayashi Sumio
Published: March 2009

200 mm wafer with 3C-SiC/SiO2/Si structure has been fabricated using 200 mm siliconon- insulator (SOI) wafer. A top Si layer of 200 mm SOI wafer was thinned down to approximately 5 nm by sacrificial oxidization, and the ultrathin top Si layer was metamorphosed into a 3C-SiC seed layer using a carbonization process. Afterward, an epitaxial SiC layer was grown on the SiC seed layer with ultra-high vacuum chemical vapor deposition. A cross-section transmission electron
microscope indicated that a 3C-SiC seed layer was formed directly on the buried oxide layer of 200 mm wafer. The epitaxial SiC layer with an average thickness of approximately 100 nm on the seed was recognized over the entire region of the wafer, although thickness uniformity of the epitaxial SiC layer was not as good as that of SiC seed layer. A transmission electron diffraction image of the epitaxial SiC layer showed a monocrystalline 3C-SiC(100) layer with good crystallinity. These
results indicate that our method enables to realize 200 mm SiC wafers.
A Thermal Model for Flash Lamp Annealing of 3C-SiC/Si Multi-Layer Systems (i-FLASiC)
Authors: Smith M. , McMahon R.A. , Skorupa Wolfgang , Voelskow M. , Stoemenos J.
Published: March 2009

This paper gives an insight into the thermal modeling of the i-FLASiC process, which is the flash lamp annealing of a 3C-SiC and silicon multilayer system. The model uses a standard heat flow model combined with an advanced multilayer optical model. Results from the model are consistent with experimentally observed phenomenon and have been used to explain diffusion mechanisms for the LPE of SiC.
Large Area DPB Free (111) β-SiC Thick Layer Grown on (0001) α-SiC Nominal Surfaces by the CF-PVT Method
Authors: Chaussende Didier , Latu-Romain Laurence , Auvray Laurent , Ucar M. , Pons Michel , Madar Roland
Published: March 2009

Thick (111) oriented β-SiC layers have been grown by hetero-epitaxy on a (0001) a-SiC substrate with the Continuous Feed-Physical Vapour Transport (CF-PVT) method. The growth rate was 68 µm/h at a pressure of 2 torr and a temperature of 1950°C. The nucleation step of the β-SiC layer during the heating up of the process was studied in order to manage first the a to b heteropolytypic transition and second the selection of the b-SiC orientation. With a adapted seeding
stage, we grew a 0.4mm thick layer almost free of Double Positioning Boundaries on a 30mm diameter sample. First observations of the layer by cross-polarised optical Microscopy are presented both in planar view and in cross section geometry.
Epitaxial SiC Formation at the SiO2/Si Interface by C+ Implantation into SiO2 and Subsequent Annealing
Authors: Voelskow M. , Panknin D. , Polychroniadis Efstathios K. , Ferro Gabriel , Godignon Philippe , Mestres Narcis , Skorupa Wolfgang , Monteil Yves , Stoemenos J.
Published: March 2009

An approach for the defect density reduction in 3C-SiC epitaxially grown on Si is to
improve the quality of the carbonized layer during the early stage of growth. For this reason the conventional carbonization process was replaced by a slower and nearer equilibrium carbonization method. Carbon is introduced by implantation into oxide of an oxidized Si substrate, near the SiO2/Si interface, and then it is transferred to the Si surface by annealing. Good quality 3C-SiC grains are formed embedded into the Si substrate, which are absolutely flat at the SiO2/Si interface.
Another advantage of the new carbonization process is the elimination of the cavities due to the suppression of Si out-diffusion.
Microfabrication of Si Column Covered with SiC Film for Electron Emitter
Authors: Nakata T. , Ohshiro Y. , Shoji A. , Okui Yoichi , Ohshima Satoru , Hayashi Yoshihiko , Nishino Shigehiro
Published: March 2009

The selective growth of Si column was carried out by depositing Au on patterned Si
(111) substrate as a solvent in chemical vapor transport method by using halides (HCl). The Si column was produced by VLS mechanism. The column was covered with SiC by conventional CVD process using HMDS ( Hexamethyldisilane ). Carbon Nano Tube ( CNT ) was deposited on Si
column covered with SiC by DC assisted µ-wave plasma CVD.
Characterization of SiC Thin Film Obtained by Magnetron Reactive Sputtering: IBA, IR and Raman Studies
Authors: Colder H. , Morales M. , Rizk Richard , Vickridge I.
Published: March 2009

Co-sputtering of silicon and carbon in a hydrogenated plasma (20%Ar-80%H2) at
temperatures, Ts, varying from 200°C to 600°C has been used to grow SiC thin films. We report on the influence of Ts on the crystallization, the ratio Si/C and the hydrogen content of the grown films. Film composition is determined by ion beam analysis via Rutherford backscattering spectrometry, nuclear reaction analysis via the 12C(d,p0)13C nuclear reaction and elastic recoil detection analysi(ERDA) for hydrogen content. Infrared absorption (IR) has been used to determine the crystalline fraction of the films and the concentration of the hydrogen bonded to Si or to C. Complementary to IR, bonding configuration has been also characterized by Raman spectroscopy. As Ts is increased, the crystalline fraction increases and the hydrogen content decreases, as observed by both ERDA and IR. It also appears that some films contain a few Si excess, probably located at the nanograin boundaries.
RBS-Channeling and EPR Studies of Damage in 2 MeV Al2+-Implanted 6H-SiC Substrates
Authors: Morilla Y. , García López J. , Battistig Gábor , Cantin J.L. , Cheang-Wong Juan Carlos , von Bardeleben Hans Jürgen , Respaldiza M.A.
Published: March 2009

6H-SiC single crystalline substrates were implanted at room temperature with 2 MeV
Al2+ ions to fluences from 2×1014 Al2+ cm-2 to 7×1014 Al2+ cm-2 and with different current densities (from 6.6 to 33×1010 Al2+ cm-2 s-1). The depth profile of the damage induced by the Al2+ ions was determined by Backscattering Spectrometry in channeling geometry (BS/C) with a 3.5 MeV He2+ beam. The BS/C spectra were evaluated using the RBX code. The samples were subsequently annealed at 1100°C in N2 for one hour, in order to analyze their structural recovery by BS/C and the amount of the remaining defects by means of Electron Paramagnetic Resonance (EPR). The results from the BS/C spectra corresponding to the as-implanted samples indicate that the damage depends strongly on the total fluence but also, although to a lesser extent, on the beam current density. The BS/C measurements reveal that all the samples, except the one implanted with the highest fluence, recover completely their original crystalline structure after the annealing. Furthermore the angular anisotropy of the EPR spectra indicates that the implanted region recovered a good crystallinity, although some residual defects were observed.
Microstructural Characterization of 3C-SiC Thin Films Grown by Flash Lamp Induced Liquid Phase Epitaxy
Authors: Ferro Gabriel , Panknin D. , Polychroniadis Efstathios K. , Monteil Yves , Skorupa Wolfgang , Stoemenos J.
Published: March 2009

Thin 3C-SiC films epitaxially grown on Si-substrate are substantially improved by the
FLASIC process, which involves irradiation with flash lamps with pulse duration of 20ms. The disadvantages of the standard FLASIC process are the undulations introduced in the SiC film due to melting of the Si-substrate and the Si mass transport near the SiC/Si interface during the flash. An improved structure was realised in order to minimize the undulations of the SiC, improving also the
quality of the film. This structure involves the deposition of a silicon overlayer (SOL) on the initial SiC layer, followed by an additional SiC capping layer acting as a source for SiC transfer by liquid phase epitaxy to the lower SiC layer. Significant mass SiC transport from the upper to the lower SiC layer through the SOL occurs during the flash. The new structure is characterized as inverse -
FLASiC. The structural characteristics of the new structure were studied by transmission electron microscopy and atomic force microscopy.
[01-15] Grown 6H-SiC Bulk Crystals Investigated by High Energy Triple Axis X-Ray Diffraction
Authors: Seitz Christoph , Herro Z.G. , Epelbaum Boris M. , Winnacker Albrecht , Hock Rainer , Magerl Andreas
Published: March 2009

A structural characterisation of the first [01-15] grown 6H SiC crystals is presented. They show a different micro domain structure outside the facetted region as compared to conventionally [0001] grown crystals. It is imposed by the reduced rotational symmetry for this direction which favours the activation of a low number of glide systems.
Specific Aspects of Type II Heteropolytype Stacking Faults in SiC
Authors: Juillaguet Sandrine , Camassel Jean
Published: March 2009

Focussing on the fine structure of excitons bound to large 2-dimensional stacking faults in a 4H-SiC matrix, we show that the intrinsic type-II nature of the band alignment, combined with the effect of the spontaneous polarization, should result in a double bound-exciton signature per well. Then, we present the first observation of a 3C-QW sandwiched between two higher energy bandgap polytypes in a 3C-SiC matrix.
Optical Characterization of Deep Level Defects in SiC
Authors: Magnusson Björn , Janzén Erik
Published: March 2009

Deep levels in 4H- and 6H-SiC are characterized by FTIR spectroscopy. Vanadium,
chromium and the silicon vacancy related center are listed together with the unidentified defects with emission and absorption in the near IR region. We suggest the UD-1, UD-3 and I-1 to be impurity related while the UD-2 and UD-4 to be intrinsic defects based on annealing behavior and the possibility to create the defect with irradiation. We have also tentatively assigned a new defect center around 1.0 eV to the carbon vacancy-antisite pair instead of the earlier assignment to the UD-
2 defect in 4H-SiC. We have shown that to get more information about the SiC samples a combination of absorption and luminescence techniques are very useful. Further, the use of below bandgap selective excitation is necessary to obtain more information about the defects present in the sample. FTIR absorption and luminescence measurements are useful tools to characterize deep levels important for both semi-insulating material as well as low doped conducting material where the free carrier lifetime is limited by deep levels.
Optical Centres with Local Vibrational Modes Created by High Temperature Annealing of Electron Irradiated 4H and 6H Silicon Carbide
Authors: Steeds John W. , Furkert S.A. , Sullivan W. , Hayes J.M. , Wright Nicolas G.
Published: March 2009

New results are presented concerning several optical centres having local vibrational modes in electron irradiated and annealed 4H and 6H SiC. Some of these centres are common to both polytypes, others have only been found in 6H SiC. They appear, typically, after annealing in the range 1000°C - 1300°C. Additional results have been obtained about mode splitting from 13C isotope enriched 6H SiC.
Recombination Enhanced Defect Annealing in 4H-SiC
Authors: Storasta L. , Carlsson F.H.C. , Bergman Peder , Janzén Erik
Published: March 2009

Recombination enhanced defect annealing of intrinsic defects in 4H-SiC, created by low energy electron irradiation, has been observed. A reduction the defect concentration at temperature lower than the normal annealing temperature of 400º C and 800°C is observed after either above bandgap laser excitation or forward biasing of a pin-diode. The presence of the defects has been studied both electrically and optically using capacitance transient spectroscopy and low temperature photoluminescence. Photoluminescence measurements show that several lines, normally detected after electron irradiation, have almost or entirely disappeared by recombination enhanced annealing at room temperature. From capacitance transient measurements, the annealing enhancement is found
to be largest for the HS2 hole trap, while the EH1 and EH3 electron traps also anneal out by recombination enhanced reaction but at a lower rate.
Room Temperature Steady State and Time Resolved PL Characterization of Ion Irradiation Induced Defects in 6H-SiC
Authors: Reitano Ricardo , Zimbone M. , Musumeci Paolo , Baeri P.
Published: March 2009

Photoluminescence (PL) and time resolved PL are well established as important
experimental techniques to study electronic properties of SiC. We studied the influence of ionimplantation on the photoluminescence peak at 423nm and the variation of the minority carrier lifetime (MCL).
Micro-Optical Characterization Study of Highly p-Type Doped SiC:Al Wafers
Authors: Wellmann Peter J. , Müller Ralf , Pons Michel , Thuaire Aurelie , Crisci Alexandre , Mermoux Michel , Auvray Laurent
Published: March 2009

We have studied the application of optical techniques for the determination of the
spatial distribution of electronic properties of highly aluminum doped p-type SiC wafers. Absorption and birefringence mapping are known to be sensitive characterization methods to determine the homogeneity of charge carrier concentration and defects in n-type SiC. In the case of highly p-type doped SiC these methods fail due to the opaque character of the material. In this paper we show that Raman spectroscopy which is a reflective method can be used in order to address the same materials properties like absorption and birefringence. The study was performed using medium doped p-type SiC:Al where optical transmission and reflection methods can be applied simultaneously.
Nonequilibrium Carrier Diffusion and Recombination in Heavily-Doped and Semi-Insulating Bulk HTCVD Grown 4H-SiC Crystals
Authors: Storasta L. , Aleksiejūnas R. , Sūdžius M. , Kadys Arunas , Malinauskas T. , Jarašiūnas Kęstutis , Magnusson Björn , Janzén Erik
Published: March 2009

We applied four-wave mixing (FWM) technique for investigation of high temperaturechemical vapour deposition (HTCVD) grown 4H-SiC samples with different doping levels. The determined minority electron and hole mobilities in heavily doped crystals at doping densities of 1019 cm-3 were found to be equal to 116 and 52 cm2/Vs. In semi-insulating (SI) crystals, the ambipolar diffusion coefficient Da = 2.6 − 3.3 cm2/s and carrier lifetimes of 1.5 – 2.5 ns have been
measured. Irradiation of SI crystals by 6 MeV electrons resulted in essential decrease of carrier lifetime down to ~ 100 ps and clearly revealed the defect-assisted carrier generation with respect to two-photon interband transitions before irradiation.
Comparison of Electrically and Optically Determined Minority Carrier Lifetimes in 6H-SiC
Authors: Reshanov Sergey A. , Pensl Gerhard
Published: March 2009

Minority carrier (hole) lifetime investigations are conducted on identical 6H-SiC p+-n structures by electrical (reverse recovery, open circuit voltage decay) and optical (time-resolved photoluminescence) techniques. The p+-n diodes are fabricated by Al implantation. Depending on the particular analysis technique, the lifetime is determined either electrically in different regions of the p+-n diode or optically in the n-type 6H-SiC epilayer and results, therefore, in different values
ranging from ≈10 ns to 2.5 µs.
Evaluation of On-State Resistance and Boron-Related Levels in n-Type 4H-SiC
Authors: Ciechonski R.R , Porro Samuele , Syväjärvi Mikael , Yakimova Rositza
Published: March 2009

Specific on-resistance Ron estimated from current density-voltage characteristics of
Schottky diodes on thick layers exhibits variations from tens of mW.cm2 to tens of W.cm2 for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with a literature reported values. Decrease in mobility with the temperature was observed and its dependencies of T–1.3 and T–2.0 for moderately doped and low doped samples respectively were estimated. From deep
level measurements by Minority Carrier Transient Spectroscopy, an influence of shallow boron related levels and D-center on dependence of on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of Ron. This suggests a major role of boron in a compensation mechanism thus resulting in high Ron.
Concentration of N and P in SiC Investigated by Time-Of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)
Authors: Acartürk T. , Semmelroth Kurt , Pensl Gerhard , Saddow Stephen E. , Starke Ulrich
Published: March 2009

The concentration of nitrogen and phosphorous in SiC bulk material and epitaxial layers was investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The advantage of TOF-SIMS of acquiring a complete mass spectrum in a single run was used to identify the most sensitive atomic ion or ionic cluster for the selected element to be monitored. For the investigation
of N with its intrinsic low ionization yield the use of a Cs containing cluster ion is necessary. Selection of a CNCs2 + cluster allows to reach a detection limit of about cN,min » 5×1016 cm-3. In the case of P the elemental ion was used. However, the adjacent mass of 30SiH influences the P peak as well as its background and has to be suppressed. This can be achieved by limiting the residual gas
re-adsorption during the measurement resulting in a detection limit of about cP,min » 5×1015 cm-3. These measurement parameters were used to investigate a single crystal SiC bulk sample grown by the modified Lely method with intentional P doping and an N doped epitaxial SiC layer sample.
SiC Crystal Growth by Sublimation Method with Modification of Crucible and Insulation Felt Design
Authors: Kim Jung Kyu , Ku Kap Ryeol , Kim Dong Jin , Kim Sang Phil , Lee Won Jae , Shin Byoung Chul , Lee Geun Hyoung , Kim Il Soo
Published: March 2009

SiC crystal boules with different shapes were prepared using sublimation physical vapor transport technique (PVT) and then their crystal quality was systematically investigated. The temperature distribution in the growth system and the crystal shape were controlled by modification of crucible and insulation felt design, which was successfully simulated using “Virtual Reactor” for flat structure design and concave structure design. The SiC polytype proved to be the n-type 6H-SiC
from the typical absorption spectrum of SiC crystal. The defect density of SiC crystal boules with concave structure was slightly lower than that of flat structure and the crystal quality of SiC crystal boules with both flat structure and concave structure was significantly improved as the SiC crystal grows during the PVT methods.
Surface Band Structure Studies of Si Rich Reconstructions on 4H-SiC(1-100)
Authors: Emtsev Konstantin V. , Seyller Thomas , Ley Lothar , Tadich A. , Broekman L. , Huwald E. , Riley J.D. , Leckey R.C.G.
Published: March 2009

We have investigated Si-rich reconstructions of 4H-SiC( 00 1 1 ) surfaces by means of low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and angleresolved ultraviolet photoelectron spectroscopy (ARUPS). The reconstructions of 4H-SiC( 00 1 1 ) were prepared by annealing the sample at different temperatures in a flux of Si. Depending on the
temperature different reconstructions were observed: c(2×2) at T=800°C, c(2×4) at T=840°C. Both reconstructions show strong similarities in the electronic structure.
Electrical Characterization of Defects in p-Type SiC Using Recombination Induced Conductivity Inversion
Authors: Krishnan Bharat , Koshka Yaroslav
Published: March 2009

Recombination-induced passivation (RIP) experiments were conducted on p-type SiC after plasma treatment in deuterium. Higher sensitivity of SIMS to deuterium allowed us to confirm that recombination-induced athermal migration of hydrogen is indeed a driving mechanism for the RIP phenomenon. Hydrogen (or deuterium) athermally migrates from the plasma-induced hydrogen- or deuterium-reach near-surface layer down to more than a micron in depth, which under certain conditions creates a sufficiently thick layer of the n-type conductivity in the originally ptype
epilayer. Thermal admittance spectroscopy was applied to investigate the defect levels in the top portion of the bandgap of the RIP-induced n-type layer. A few different levels located close to the conduction band of the originally p-type material were investigated.
Technological Aspects of Ion Implantation in SiC Device Processes
Authors: Negoro Yuki , Kimoto Tsunenobu , Matsunami Hiroyuki
Published: March 2009

Technological aspects of ion implantation in SiC device processes are described.
Annealing techniques to suppress surface roughening of implanted SiC (0001) are demonstrated. Trials to achieve a low sheet resistance are described for n-type and p-type doping. Implantation into the (11-20) face is also presented. Electrical behaviors of implants near implanted tail regions are discussed based on experiments.