bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Radiation in Solid during SiC Sublimation Growth
Authors: Nishizawa Shin-ichi , Nakashima Shin-ichi , Kato Tomohisa 
Published: April 2011

AbstractThe effect of infrared absorption on SiC sublimation growth was numerically investigated. At first, absorption coefficient was estimated as function of doping concentration. Then temperature distribution inside a crucible was numerically analyzed with taking account of absorption in growing crystal. It was pointed out that temperature distribution in a growing crystal strongly depends on absorption coefficient, i.e. doping concentration. As increasing the absorption coefficient, the growth front temperature and temperature gradient inside a growing crystal increase. It might cause large thermal stress and affect the grown crystal quality. This agrees well with growth features in experiment. The growth condition should be determined with taking account of absorption coefficient, i.e. doping concentration.
Crystal face and C/Si ratio Dependence of Phosphorus Doping by SiC Epitaxial Growth
Authors: Tawara Takeshi , Ueki Yuko , Nakamura Shunichi , Gotoh Masahide , Yonezawa Yoshiyuki , Nishiura Masaharu 
Published: April 2011

AbstractThe dependence of phosphorus doping on crystal face and C/Si ratio in the epitaxial growth of 4H-SiC using phosphine were investigated. Phosphorus incorporation was highest on off-axis (000-1) and lowest on off-axis (0001). Phosphorus incorporation on (11-20) came between that on off-axis (0001) and (000-1). With increasing C/Si ratio from 0.5 to 2.5, phosphorus incorporation increased on (11-20) and off-axis (000-1). Phosphorus incorporation on off-axis (0001) showed unclear C/Si ratio dependence. On (000-1), the highest phosphorus concentration of 2 × 1018cm-3 was obtained by an increasing PH3 flow rate. The roughness, growth rate, and surface morphology of the high phosphorus doped epilayer were investigated.
Process-Induced Deformations and Stacking Faults in 4H-SiC
Authors: Okojie Robert S , Huang Xianrong , Dudley Michael , Zhang Ming , Pirouz Pirouz 
Published: April 2011

AbstractWe used Film Stress Measurement (FSM), Transmission Electron Microscopy (TEM), and High-Resolution X-ray Diffraction (HRXRD) techniques to obtain further knowledge with respect to the deformation, warpage, and stacking faults (SF's) that are induced in n-type 4H-SiC wafers and epilayers when subjected to mechanical polishing and high temperature (1150 oC) processing.
Development of a high-growth rate 3C-SiC on Si CVD process
Authors: Reyes M. , Shishkin Y. , Harvey S. , Saddow S. E. 
Published: April 2011

AbstractGrowth rates from 10 to 38 μm/h were achieved for heteroepitaxial 3C-SiC on Si (100) substrates by using the propane-silane-hydrogen gas chemistry with HCl as a growth additive. A low-pressure horizontal hot-wall CVD reactor was employed to perform the deposition. The growth rate dependences on silane mole fraction, the process pressure and the growth time were determined experimentally. The growth rate dependence on silane mole fraction was found to follow a linear relationship. The 3C-SiC films were characterized by Normaski Optical Microscopy, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Atomic Force Microscopy and X-ray Diffraction. The X-ray rocking curve taken on the (002) diffraction plane displayed a FWHM of 360 arcsec which indicates that the films are monocrystalline.
Laser Endotaxy and PIN Diode Fabrication of Silicon Carbide
Authors: Tian Zhaoxu , Quick Nathaniel R , Kar Aravinda 
Published: April 2011

AbstractA laser solid phase diffusion technique has been utilized to fabricate endolayers in n-type 6H-SiC substrates by carbon incorporation. X-ray energy dispersive spectrometry (XEDS) analysis showed that the thickness of endolayer is about 100 nm. High resolution transmission electron microscopy (HREM) images indicate that the laser endotaxy process maintains the crystalline integrity of the substrate without any amorphization. The resistivity of the endolayer was 1.1 ¡Á105 &#61527;&#8226;cm and 9.4 ¡Á104 &#61527;&#8226;cm after annealing at 1000&#61616;C for 10 min. These resistivities provide device isolation for many applications. The silicon carbide endolayer was doped with aluminum using a laser doping technique to create p-region on the top surface of the endolayer in order to fabricate PIN diodes.
Impact of EBAS annealing on sheet resistance reduction for Al-implanted 4H-SiC(0001)
Authors: Shibagaki Masami , Egami Akihiro , Kumagai Akira , Numajiri Kenji , Watanabe Fumio , Haga Shigetaka , Miura Kuniaki , Miyagawa Shingo , Kudoh Naohiro , Suzuki Tomoyuki , Satoh Masataka 
Published: April 2011

AbstractIn this paper, we demonstrate that high temperature and short time EBAS annealing is effective to obtain low sheet resistance without surface roughening in heavily Al-implanted 4H-SiC (0001) samples (Al concentration: 1.0 × 1021 /cm3, thickness: 0.3 microns, total dose: 2.6 × 1016 /cm2). The sheet resistance and rms surface roughness of the sample annealed at 1800 °C for 0.5 min is estimated to be 4.8k ohm/sq. and 0.82 nm, respectively. Also, we discuss the advantage of EBAS annealing for the suppression of surface roughening during annealing.
Ti/AlNi/W Ohmic Contacts to P-Type SiC
Authors: Tsao Bang-Hung , Lawson Jacob , Scofield James 
Published: April 2011

AbstractImproved AlNi-based ohmic contacts to p-type 4H-SiC have been achieved using low energy ion (Al+) implantation, the addition of a thin Ti layer, and a novel two-step implant activation anneal process. Resistivities sometimes as low as 5×10−5 Ω-cm2 were reached by doping the surface region of lightly p-doped 4H-SiC epilayers via low energy Al+ implantation. Acceptor activation was achieved by annealing the samples with a 1400+1700°C two-step sequence in an Ar atmosphere, which also yielded improved surface morphology when implanted samples were capped with photo resist during the anneals. In this study, Ti/AlNi/W contacts on implanted layers were compared to Ti/AlNi/Au contacts. Even though the resistivities are higher than those of the Ti/AlNi/W system, the reduced anneal temperature, 650°C for Ti/AlNi/Au compared to 950°C for Ti/AlNi/W implies that Ti/AlNi/Au is a promising stacking configuration. Furthermore, the effects of a longer 30 minute anneal time at 600 − 700°C, in atmospheric pressure Ar ambients was observed. Namely, the 2 minute annealing cycle used for the Ti/AlNi/W study resulted in higher anneal temperatures before ohmic characteristics were seen. This same anneal time was not sufficient for the Ti/AlNi/Au samples, whereas increasing the cycle time to 30 minutes resulted in ohmic behavior at a much lower temperature. Increasing the anneal time however, had little or no impact on reducing the required anneal temperature of the Ti/AlNi/W.
Alternative Magnesium Calcium Oxide Gate Dielectric for Silicon Carbide MOS Application
Authors: Stodilka Danielle , Gerger A. P. , Hlad M. , Kumar P. , Gila B. P. , Singh R. , Abernathy C. R. , Pearton S. J. , Ren F. 
Published: April 2011

AbstractFilms of MgO and MgCaO ternaries were grown at low temperature as dielectrics on 6H-SiC by gas-source MBE. MgO grown at 300 and 400°C revealed crystallites textured toward the (111) orientation on SiC (0001). A solid-solution Mg.75Ca.25O ternary was grown having a minimal lattice mismatch and low root mean square (RMS) roughness of 0.5 nm. SiC pretreatments in UV-ozone reduced carbon contaminants on the surface of SiC, but resulted in the increase of fixed oxide charge in the oxide/SiC interface. Electrical breakdown fields >3.5 MV cm-1 and low density of interface states on the order of 1011 cm-2eV-1 were achieved for a Mg.75Ca.25O ternary grown at 300°C. These oxides are presented for the first time as low temperature alternatives to SiO2 gate dielectrics for SiC MOS applications.
Nanofabrication of Vertically Aligned Carbon Nanofibers for Contact Characterization
Authors: Ominami Yusuke , Ngo Quoc , Suzuki Makoto , Mcilwrath Kevin , Jarausch Konrad , Cassell Alan M , Li Jun , Yang Cary Y 
Published: April 2011

AbstractRecent studies in nanostructural characterization for on-chip interconnect applications using carbon nanofibers (CNFs) are presented. In this paper, we propose a novel technique, for the purpose of characterizing interfacial structures of vertically aligned CNFs for cross-sectional imaging with scanning transmission electron microscopy (STEM). In this technique, vertically aligned CNFs are selectively grown, by plasma-enhanced chemical vapor deposition (PECVD), on a substrate comprising a narrow strip (width ~100nm) fabricated by focused ion beam (FIB). Using high-resolution STEM, we show that CNFs with diameters ranging from 10 -100 nm exhibit very similar graphitic layer morphologies at the base contact interface.
Poly-L-Lysine Mediated Fractal Titania Structures
Authors: Sowards Laura A. , Singh Kristi M. , Drummy Lawrence F. , Kasten Linda S. , Tomczak Melanie M. , Naik Rajesh R. 
Published: April 2011

AbstractWe demonstrate here the use of Poly-L-lysine to mediate the mineralization of fractal titania structures.
Time Resolved Dynamics of Femtosecond Laser Ablation of Si (100) with Thin Thermal Oxide Layers (20 - 1200 nm)
Authors: McDonald Joel Patrick , Mistry Vanita R. , Nees John A. , Yalisove Steven M. 
Published: April 2011

ABSTRACTFemtosecond (fs = 10−15 sec.) laser ablation of Si(100) with thermally grown oxide films was studied with pump/probe imaging techniques in order to determine the role of film thickness on ablation dynamics. Two different imaging geometries were used in this study. Front view images were formed with the reflection of a delayed probe pulse from the area of a sample irradiated with a pump pulse. By changing the delay between the pump and probe pulses, images were obtained showing the evolution of the surface as a function of time (0 – 12 ns after the arrival of the pump pulse). The side view imaging technique, also known as shadowographic imaging, an image was formed of a delayed probe pulse which passed through the ablation plume produced by a pump pulse parallel to the sample surface. Both laser induced shock wave propagation and material removal were observed to change with increased thermal oxide thickness.
Surface Modification of Glassy Polymeric Carbon by Glow Discharge
Authors: Abidzina Volha , Tereshko I. , Elkin I. , Zimmerman R.L. , Muntele I. , Muntele C. , Minamisawa R.A. , Chhay B. , Ila D. 
Published: April 2011

ABSTRACTWe have studied the effects of low energy ion beam produced by glow discharge on glassy polymeric carbon (GPC) produced at pyrolysis temperature ranging from 200C to 1000C. The pristine and irradiated GPC were studied using FTIR, Raman Spectrometry indicating changes at the surface of the GPC samples.
Atomistic Studies of Crack Branching at Bimaterial Interfaces: Preliminary Results
Authors: Krishnan Sriram , Buehler Markus J 
Published: April 2011

ABSTRACTIn this paper, we summarize recent progress in applying atomistic studies of cracking along interfaces of dissimilar materials under quasi-static crack growth conditions. We consider two linear-elastic material strips in which atoms interact with harmonic potentials, with a different spring constant in each layer leading to a soft and a stiff strip. The two strips are bound together with a tunable potential, which allows to independently control the interface and bulk fracture surface energy. An initial crack serves as initiation point for the failure. This provides a model system to investigate how elastic properties and interface strength interplay and determine the crack growth direction, leading to either interfacial cracking or branching into the film material. We observe a clear transition to interface failure when the interface fracture energy is less than 80% of the bulk fracture energy. We further find that branching in the film material is controlled by the elastic properties of the film material, suggesting interfacial cracking for extremely soft films and branching for stiffer films. Analysis of the virial stress field around the crack suggests that the circumferential hoop stress controls the branching behavior.
Osteoblast Response to Amino Acid-modified Surfaces
Authors: Todd Simon , Rawsterne Rachel , Ulijn Rein , Gough Julie 
Published: April 2011

ABSTRACTThe behavior of cells at the material surface is of critical importance in the design of biomaterials. To understand and control cell responses to surfaces, different surface chemistries are commonly compared. In this study we exploit the chemical diversity of the 20 naturally occurring amino acids to make 20 surfaces with different chemical properties. The biological response of osteoblasts to these surfaces was examined. The osteoblast response to the surfaces was found to be dependant on the wettability of the surface with polar amino acid surfaces (Cys<Ser<Thr<Gln<Asn) promoting osteoblast spreading more than hydrophobic aromatic amino acid surfaces (Phe <Tyr <Trp), aliphatic amino acid surfaces (Leu<Ile<Val<Ala<Met<Gly), and Pro. The surface charge also affected the cellular response with positively charged amino acid surfaces (His<Arg<Lys) producing a higher percentage of spreading cells compared to the negatively charged surfaces (Asp<Glu). Amino acid surfaces provide a range of well defined chemical functionalities that are useful in studying the interactions of cells with material surfaces.
Culture of Mammalian Cells on Single Crystal SiC Substrates
Authors: Coletti Camilla , Jaroszeski Mark J. , Hoff Andrew M. , Saddow Stephen E. 
Published: April 2011

ABSTRACTCrystalline silicon carbide (SiC) has the potential to become an important biomaterial and a versatile interface between the electronic and biological world. In this work, single crystal SiC biocompatibility is investigated by culturing mammalian cells directly on SiC substrates. The cell morphology and the quality of the cell adhesion have been studied using fluorescence microscopy, while MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays have been performed to quantify cell viability and number. Standard culture-wells and silicon (Si) substrates were used as controls in the final assessment of crystalline SiC biocompatibility.
DNA Hydrogels
Authors: Um Soong Ho , Park Nokyoung , Luo Dan 
Published: April 2011

ABSTRACTA hydrogel has been developed into a promising scaffold for cell encapsulation or drug delivery useful in various biorelated research areas. DNA, with its outstanding specificity and flexibility and intrinsic biocompatibility, has been utilized as a new building block in the construction of this new three dimensional material-a DNA based hydrogel. Here, we report the synthesis, properties and applications of a DNA based hydrogel system. The DNA hydrogels are entirely constructed from branched DNA building blocks such as X-shaped DNA (X-DNA), Y-shaped DNA (Y-DNA), and T-shaped DNA (T-DNA) through an enzyme-catalyzed reaction. These DNA hydrogels can be easily patterned into different sizes with millimeter or micrometer scale and different shapes including cylindrical, rectangular, cross, star, and even the “CORNELL” logo. By adjusting the initial concentrations and original shapes of the different building blocks, the external and internal morphology and chemical/physical properties of the DNA hydrogel were easily tuned: The X-DNA based hydrogel (X-DNA gel) showed both the most swelling degree and mechanical strength as well as the higher resistance to chemical and biological degradation. Inspired by these characteristics of the DNA hydrogels, we have developed them into a drug delivery system, an artificial extracellular matrix, and even a cell-free protein producing template.
Photo-oxidation of Ge Nanocrystals: Kinetic Measurements by In Situ Raman Spectroscopy
Authors: Sharp I. D. , Xu Q. , Yuan C. W. , Beeman J. W. , Ager J. W. , Chrzan D. C. , Haller E. E. 
Published: April 2011

ABSTRACTGe nanocrystals are formed in silica by ion beam synthesis and are subsequently exposed by selective HF etching of the silica. Under ambient conditions, the exposed nanocrystals are stable after formation of a protective native oxide shell of no more than a few monolayers. However, under visible laser illumination at room temperature and in the presence of O2, the nanocrystals rapidly oxidize. The oxidation rate was monitored by measuring the Raman spectra of the Ge nanocrystals in-situ. The intensity ratio of the anti-Stokes to the Stokes line indicated that no significant laser-induced heating of illuminated nanocrystals occurs. Therefore, the oxidation reaction rate enhancement is due to a photo-chemical process. The oxidation rate varies nearly linearly with the logarithm of the laser intensity, and at constant laser intensity the rate increases with increasing photon energy. These kinetic measurements, along with the power dependencies, are described quantitatively by an electron active oxidation mechanism involving tunneling of optically excited electrons through the forming oxide skin and subsequent transport of oxygen ions to the Ge nanocrystal surface.
Terahertz Detection Related to Plasma Excitations in Nanometer Gate Length Field Effect Transistor.
Authors: Knap Wojciech , El Fatimy A. , Tauk R. , Tombet S. Boubanga , Teppe F. 
Published: April 2011

ABSTRACTThe channel of nanometre field effect transistor can act as a resonant cavity for plasma waves. The frequency of these plasma waves is in the Terahertz range and can be tuned by the gate length and the gate bias. During the last few years Terahertz detection and emission related to plasma wave instabilities in nanometre size field effect transistors was demonstrated experimentally. In this work we review the recent results on sub-THz and THz detection by 50-300nm gate length III-V HEMTs and Si MOSFETs. We present experimental results on the resonant and nonresonant (overdamped) plasma wave detection and discuss possible applications of nanometre field effect transistors as new detectors of THz radiations.
Nano-sized Crystals of Silicon Embedded in Silica Glass: Large Scale Models and Aspects of the Electronic Structure
Authors: Kroll Peter , Schulte Hendrik J. 
Published: April 2011

ABSTRACTWe construct quasi-spherical Si nanocrystallites consisting of 17, 29, 47, 71, and 99 atoms with diameters from 0.8 to 1.6 nm embedded in an SiO2 network. All atoms have saturated bonds: Si is four-fold connected and O is two-fold connected. The models comprise 400-600 atoms and have lattice parameters of about 2 nm. The networks are subjected to a bond switching algorithm yielding models of nanocrystalline Si embedded in amorphous silica.Subsequently, we employ density functional methods. As a result of the DFT-optimization we find that the Si nanocrystals are free of defects at the interface to the host matrix. Si-Si distances within the Si nanocrystallites are strained, the strain itself tailors off to the suboxide interface. The excess energy of the optimized models with respect to crystalline silicon and vitreous silica scales linearly with the surface of the Si nanoparticles. The interfacial energy of the nc-Si/SiO2 interface is calculated to 1.5 J/m2. We observe an increase of the band gap with decreasing cluster size due to the quantum-confinement effect. The highest occupied states of the valence band are located at Si-Si bonds close to the interface; the corresponding charge density forms a shell-like structure around the central core of the nanocrystal. The lowest unoccupied states are centered within the nanocrystal.
Gas Cluster Ge Infusion for Si(1−x)Ge(x)Strained-Layer Applications
Authors: Tetreault Thomas G. , Shao Yan , Huang Mengbing , Hautala John 
Published: April 2011

ABSTRACTMaterials processing with a gas cluster ion beam (GCIB) is an emerging technology that has been shown to produce novel material properties in the very near-surface (<40nm) regime. We have termed the process of doping with GCIB, infusion. Its principal characteristic enables room temperature shallow processing with high concentration gradients and no sharp interfaces. Results are presented from an investigation of GCIB GeH4 infusion into Si(100) substrates for the purpose of producing a strained Si(1-x)Ge(x) layer relative to the Si substrate. The as-infused samples exhibit surface Ge concentrations up to 100%, with a steep concentration gradient over ∼40 nm. Specifically, a broad series of post-processing tube-furnace anneals was investigated over a temperature range of 400 °C to 1200 °C and the samples were analyzed by channeling/RBS to look at quality of recrystallization and for evidence of strain in the lattice. Some anneal schedules included a VLTA (very low temperature anneal) first step followed by subsequent HTA (high temperature anneal). Evidence is shown for improved results with no Ge loss using two-step anneals. Channeling analysis was performed along the <100> and <110> directions relative to the Si(100) substrate. Measurements of the min for both the Ge and Si were made to assess crystal quality and to determine the degree of epitaxial alignment with the Si lattice. High-resolution axial scans along <110> were performed on selected samples to look for strain relative to the Si lattice. SIMS analysis of higher temperature anneals showed significant diffusion of Ge. Some samples were also examined by cross-sectional TEM. The best infusion samples show crystal quality comparable to a commercially available epi-grown Si75Ge25 control sample.
Biological Properties of Nanocrystalline Silicon Particles for Biomedical Applications
Authors: Sato Keisuke , Yanagisawa Satoshi , Funakubo Akio , Fukui Yasuhiro , Hirakuri Kenji , Higami Tetsuya 
Published: April 2011

ABSTRACTWe have studied the biological properties of nanocrystalline silicon (nc-Si) particles after injection at various places in a mouse. The nc-Si particles with a size of 2.5 nm and a concentration of 1.3 mg/ml were dispersed in a normal saline solution (NSS). The NSS dispersible nc-Si particles were safely injected into the mouse. When the nc-Si particles in the NSS were directly injected into the subcutaneous vein and the coronary artery of the heart by syringe, the condition of bloodstream at each place was confirmed by the red luminescence (peak wavelength at 720 nm) from the nc-Si particles under the ultraviolet (UV) light-irradiation. Moreover, the nc-Si particles in the NSS, which were injected into the vein in the sole, smoothly flowed to the small intestine, and the smooth fluidity of nc-Si particles was also observed for the condition of the peristalsis of the small intestine. The nc-Si particles in the small intestine emitted red light during peristalsis under the UV light-irradiation. The red luminescence at each place was very bright and could be clearly seen with the naked eye. These phenomenons were achieved by the utilization of the harmless material, the formation of nc-Si particles with the single-order-size and the realization of the stable surface modification to the nc-Si particles.