bluuebunny/crossref_metadata_2025_split huggingface dataset:
First-principles Studies of Phase Stability and the Neutral Atomic Vacancies in LiNbO3, NaNbO3 and KNbO3
Authors: Shigemi Akio , Wada Takahiro 
Published: April 2011

AbstractWe overall evaluated the enthalpies of formation and the formation energies of neutral vacancies in ANbO3 (A = Li, Na, K) using a plane-wave pseudopotential method within a density functional formalism. The LiNbO3 phase with the LiNbO3-type structure was confirmed to have lower enthalpy of formation than that with perovskite- or ilmenite-type structure. The NaNbO3 (R3c) and KNbO3 (Bmm2 and R3m) phases with the lowest symmetry were found to have the lowest enthalpy of formation. The formation energy of a A vacancy was found to be the lowest under an oxidizing atmosphere and that of an O vacancy was found to be the lowest under a reducing atmosphere. The formation energy of a Nb vacancy was the highest under both oxygen-rich and -poor conditions. These results are in agreement with the empirical rule that B site defects in perovskite-type oxide do not exist.
Out-of-phase Boundary (OPB) Nucleation in Layered Oxides
Authors: Zurbuchen Mark , Lettieri James , Jia Yunfa , Carim Altaf H. , Streiffer Stephen K. , Schlom Darrell G. 
Published: April 2011

AbstractOut-of-phase boundaries (OPBs), planar faults between regions of a crystal that are misaligned by a fraction of a unit cell dimension, occur frequently in materials of high structural anisotropy. Rarely observed in the bulk, OPBs frequently exist in epitaxial films of layered complex oxides, such as YBCO-type, Aurivillius, and Ruddlesden-Popper phases, and frequently propagate through the entire thickness of a film, due to their large offset and the improbability of opposite-sign OPB annihilation. OPBs have previously been demonstrated to have a significant impact upon properties, so it is important to understand their generation. These faults arise through the same few mechanisms in the various layered complex oxides.An effort is made to unify the discussion of nucleation of these defects, common to layered oxide materials. OPBs can nucleate at the film-substrate interface (primary) via steric, chemical, or misfit mechanisms, or post-growth (secondary) through crystallographic shear during decomposition of volatile components. Examples of the mechanisms observed during high-resolution transmission electron microscopy (HRTEM) study of Aurivillius and Ruddlesden-Popper phases are presented. A method for estimating the relative OPB density in a film from correlation of x-ray diffraction (XRD) θ-2θ data with TEM information on OPBs is presented.
Non-Destructive Electro- and Photo-Luminescence Imaging of Dislocations in SiC Epitaxy
Authors: Liu Kendrick , Stahlbush Robert E , Caldwell Joshua D , Hobart Karl D , Kub Francis J , Sumakeris Joseph J 
Published: April 2011

AbstractElectroluminescence (EL) and photoluminescence (PL) imaging and stressing techniques are presented that are useful characterization tools for SiC epitaxial layers grown for power devices. Both EL and PL techniques are non-destructive, and the PL imaging is non-contact. These features are important for qualifying epitaxial layers before subjecting the layers to the time-consuming and costly process of device fabrication. By imaging at various emission spectral bands, the spectral information are correlated to the geometric features in the images. This correlation enables the differentiation of dissimilar defects having similar geometric shapes. Row average plots of images at various emission spectral bands revealed that threading dislocations (TDs) have strong emission above 900 nm and that basal plane dislocations (BPDs) have a broad spectral emission that are most easily distinguished in the range between 738 nm and 870 nm. The correlation between spectral information and the image features clearly distinguished TDs and BPDs from other defects, such as, organic substance and other surface blemishes. In addition to identifying the defects, understanding their origin can be useful in developing low-defect growth techniques. The defect origination depth is one of the important information for understanding defect origin. Two schemes for determining the defect origination depth are presented. Varying the focus depth by adjusting the objective lens height is a crude but quick scheme. Stressing the epilayer to grow the BPDs till they reach the surface or the epilayer/substrate interface is more time-consuming but more accurate. The scheme of varying the focus was demonstrated using PL imaging on a 50-mm thick n- epilayer with no p+ anode layer. Adjusting the focus on a partial dislocation in the n- epilayer revealed segments of the partial coming more in focus near the epilayer/substrate interface, suggesting the defect origination depth was at or near the interface. The stress and growth scheme was demonstrated on a straight string of half loop defects in a 100-mm thick n- epilayer. During electrical stressing, BPDs emanated from the half loops and eventually propagated to the surface at a lateral distance of 250 mm. With the basal plane at an 8° offcut from the surface, the origin of the BPDs was calculated to be 35 mm below the surface, suggesting the defects to be introduced during the growth process. Either EL or PL technique can be used with any of these two schemes to determine the defect origination depth. However, the PL technique has the benefit that the p+ anode layer and the procedure for forming a metal grid are not required.
Perchlorosilanes and Perchlorocarbosilanes as Precursors to Silicon Carbide
Authors: Sevastyanov Vladimir , Ezhov Yurij , Pavelko Roman , Kuznetsov Nikolaj 
Published: April 2011

AbstractHomologues with the general stoichiometry a(SiCl4) : bSi : cC : d(SiC) are shown to be potential precursors for the low-temperature gas-phase synthesis of silicon carbide. Thermal decomposition of these precursors yields the chemically stable gaseous species SiCl4 and condensed Si, C, SiC, SiC+Si, or SiC+C. Thermodynamic modeling of the thermal decomposition of octachlorotrisilane, Si3Cl8, is used to analyze the key features of the thermolysis of perchlorosilanes with the general stoichiometry a(SiCl4) : bSi. The equilibrium compositions of reaction products in the Si3Cl8+CO system are determined. This reaction system enables low-temperature (400 – 1200 K) synthesis of silicon carbide.
Multiplication of Basal Plane Dislocations via Interaction with c-Axis Threading Dislocations in 4H-SiC
Authors: Chen Yi , Dhanaraj Govindhan , Dudley Michael , Zhang Hui , Ma Ronghui , Shishkin Yevgeniy , Saddow Stephen E 
Published: April 2011

AbstractSilicon carbide (SiC) substrates with chemical vapor deposition (CVD) grown epilayers have been characterized by synchrotron white beam X-ray topography (SWBXT). Large numbers of circular basal plane dislocation loops (BPDs) were observed in the substrate which were anchored by threading screw dislocations (SDs). Threading edge dislocations (TEDs) are not observed to play an important role in the multiplication of BPDs. A SD-assisted “conservative climb” model is proposed to explain the multiplication of BPDs during growth and/or post-growth processes. BPDs are shown to multiply on adjacent parallel basal planes via single SD-assisted as well as opposite sign SD-pair-assisted “conservative climb”.
Demonstration of Hybrid Silicon-on-Silicon Carbide Wafers and Electrical Test Structures with Improved Thermal Performance
Authors: Whipple Steven G. , Torvik John T. , Treece Randolph E. , Bernacki Jeffrey T. 
Published: April 2011

AbstractMultiple 50 mm hybrid Si-on-SiC substrates consisting of thin film [100] Si (1 μm) on bulk semi-insulating [0001] 6H-SiC wafers were fabricated using low-temperature (150°C) wafer bonding and slicing techniques. A set of samples were prepared comparing various thicknesses of SiO2 (60, 120, 190, 240 and 520 nm) as an intermediate bonding layer between the two materials. A variety of test structures such as Van der Pauw structures, linear transfer-length measurement arrays and resistors were fabricated in the Si layers using standard Si processing (such as lithography, B-diffusion, etching and oxidation) in order to characterize the robustness as well as the electrical and thermal properties of the hybrid substrates. Bulk Si and Si-on-insulator (SOI) substrates were used for comparison. We report the Si layers on the hybrid Si-on-SiC substrates to be device-grade in terms of mobility and crystal structure, and that their device-to-device electrical isolation properties are superior to those of bulk Si and comparable to those of SOI. Furthermore, electrical test structures on hybrid Si-on-SiC substrates exhibit vastly superior heat dissipation compared to equivalent devices on bulk Si or SOI. Specifically, the temperature rise can be as much as 102°C lower in resistor devices made on Si-on-SiC (Tj= 191°C) compared to on bulk Si (Tj= 293C) under high-power density operation (67 kW/cm2). We also describe the effects of intermediate oxide thickness on thermal resistance.
Simultaneous Formation of Ohmic Contacts for Both N- and P-Type 4H-Sic Using Nial-Based Contact Materials
Authors: Tsukimoto Susumu , Onishi Toshitake , Ito Kazuhiro , Murakami Masanori 
Published: April 2011

AbstractIn order to simplify a fabrication process of silicon carbide power MOSFETs (metal oxide semiconductor field effect transistors), development of a simultaneous formation process of ohmic contacts to both the p-well and n-source regions of the SiC devices using same contact materials and one step annealing was challenged. We succeeded to develop NiAl-based contact materials which provided ohmic behaviors for both n- and p-type 4H-SiC after one step annealing. The Ni/Al and Ni/Ti/Al ohmic contacts were prepared by depositing sequentially Ni, (Ti) and Al layers with various layer thicknesses onto the n- and p-type SiC substrates which were doped with N at 1 × 1019 cm-3 and with Al at 8 × 1018 cm-3, respectively. The Ni(50 nm)/Al(5 ~ 6 nm) contacts showed ohmic behaviors for both the n- and p-type SiC substrates after annealing at 1000 °C. The Ni(20 nm)/Ti(50 nm)/Al(50 ~ 70 nm) contacts showed ohmic behaviors for both the n- and p-type SiC substrates after annealing at a lower temperature of 800 °C. The specific contact resistances of these contacts were measured to be in the order of 10-3 Ω-cm2 for both p- and n-type SiC, and were found to have strong dependence of the Al layer thicknesses of materials. The interfacial microstructures of the NiAl-based contacts were also observed by transmission electron microscopy (TEM) to understand the current transport mechanism through the metal/SiC interfaces.
Development of A 4H-SiC CMOS Inverter
Authors: Hull Brett Adam , Ryu Sei-Hyung , Fatima Husna , Richmond Jim , Palmour John W. , Scofield James 
Published: April 2011

AbstractIn this paper we report the first 4H-SiC CMOS inverter, which was designed to be integrated in the process flow of a 4H-SiC power DMOSFET. The channels of both of the n channel and p-channel MOSFETs of the inverter were 50 um wide by 3 um long. NMOSFET threshold voltage (VTH) ranged from 4.4 V at 25°C to 2.2 V at 250°C and PMOSFET VTH ranged from -4.75 V at 25°C to just under -4 V at 300°C. The transfer threshold voltage (Vm) of the 4H-SiC CMOS inverter was in a very tight range of 2.8 V to 2.9 V over the entire temperature range of 25°C to 300°C when using a drive voltage (VDD) of 10 V.
Biocompatible Polymeric Nanoparticles and Films Containing Hydrophobic Quantum Dots
Authors: Lee Jisook , Kwon Ick Chan , Woo Kyoungja , Chung Hesson 
Published: April 2011

ABSTRACTMicro- or nano-particles encapsulating hydrophobic quantum dots were prepared by the emulsion technique. Films containing quantum dots were also prepared by film casting methods. Quantum dots without hydrophilic coating were directly mixed with polymer solution to prepared extremely stable films or particles that do not phase-separate with time. The surface of the particles or films could be modified to have different hydrophilicity and/or functional groups. Particles with 1.5 ± 0.16 μm and 320 ± 26 nm in diameters and films of 300 μm in thickness were prepared. NIH 3T3 and EMT-6 were culture on the films containing quantum dots for 8 – 20 h. Compared to the control, quantum dot were delivered directly and efficiently into the cells without toxicity. When implanted near tumor cells in Balb/C mice, quantum dots migrated from the films into the tumor cells for at least 3 days. Considering that the quantum dot dispersion in aqueous media is relatively unstable and difficult to handle, our stable particles or films containing hydrophobic quantum dots can become versatile probes for biological applications.
Advances in SiGeSn/Ge Technology
Authors: Soref Richard , Kouvetakis John , Menendez Jose 
Published: April 2011

ABSTRACTWe recently reported the CVD growth of binary Ge1−ySny and ternary Ge1−ySixSny alloys directly on Si wafers using SnD4, Ge2H6 (di-germane), SiH3GeH3, and (GeH3)2SiH2 sources. Ge1−ySny is an intriguing infrared material that undergoes an indirect-to-direct bandgap transition for y ≥ 0.09. In addition, we have found that Ge1−ySny layers have ideal properties as templates for the subsequent deposition of other semiconductors: (a) they are strain-relaxed and have low threading-defect densities (105 cm−2) even for films thinner than 1 μm; (b) their low growth temperatures between 250°C and 350°C are compatible with selective growth, and the films possess the necessary thermal stability for conventional semiconductor processing (up to 750°C depending on composition); (c) they exhibit tunable lattice constants between 5.65 Å and at least 5.8 Å, matching InGaAs and related III-V systems; (d) their surfaces are extremely flat; (e) they grow selectively on Si and not on SiO2; and (f) the film surface can be prepared by simple chemical cleaning for subsequent ex-situ epitaxy. The incorporation of Sn lowers the absorption edges of Ge. Therefore, Ge1−ySny is attractive for detector and photovoltaic applications that require band gaps lower than that of Ge. Spectroscopic ellipsometry and photoreflectance experiments show that the direct band gap is halved for as little as y = 0.15. Studies of a Ge0.98Sn0.02 sample yield an absorption coefficient of 3500 cm−1 at 1675 nm (0.74 eV). Thus infrared detectors based on Ge0.98Sn0.02 could easily cover the U-(1565 nm-1625 nm), L-(1565 nm-1625 nm), and C-(1530 nm-1565 nm) telecomm bands. Photoluminescence studies show bandgap emission on thin GeSn layers sandwiched between higher bandgap SiGeSn barriers. We have made advances in p and n doping of GeSn and present results on electrical characterizations. GeSn also has application in band-to-band laser heterodiodes. The ternary system Ge1−x−ySixSny grows on Ge1−ySny-buffered Si. It represents the first practical group-IV ternary alloy, since C can only be incorporated in minute amounts to the Ge-Si network. The most significant feature of Ge1−x−ySixSny is the possibility of independent adjustment of lattice constant and band gap. For the same value of the lattice constant one can obtain band gaps differing by more than 0.2 eV, even if the Sn-concentration is limited to the range y < 0.2. This property can be used to develop a variety of novel devices, from multicolor detectors to multiple junction photovoltaic cells. A linear interpolation of band gaps lattice constants between Si, Ge and α-Sn shows that it is possible to obtain SiGeSn with a band gap and a lattice constant larger than that of Ge. We shall use this feature to make a tensile-strained Ge-on-SiGeSn telecomm detector with improved performance. The tensile-strain-induced direct gap of Ge can be used also for laser diodes and electroptical modulators.
Fabrication and Characteristics of Low Doped Gallium-Zinc Oxide Thin Film Transistor
Authors: Verma Ved Prakash , Kim Dohyun , Jeon Minhyon , Choi Wonbong 
Published: April 2011

ABSTRACTThin film transistor (TFT) with low (1%wt) Ga-doped ZnO (GZO) as an active channel on SiO2/Si substrate has been fabricated at room temperature by rf-magnetron sputtering. The devices show a mobility of 5.7 cm2/V.s at low operation voltage (<5V), a low turn-on voltage of 0.5 V and sub-threshold swing of 85 mV/decade. The TFT device performance is significantly affected by vacuum-level and annealing temperature, which can be attributed to the removal of chemisorped oxygen in the active channel surface. Low doped GZO is a new class of high performance TFT channel material that is easy to process.
Strain-Based Electrical Properties of Systems of Carbon Nanotubes Embedded in Parylene
Authors: Brame Jon , Getty Stephanie , Goodsell Johnathan , Allred David Dean 
Published: April 2011

ABSTRACTWe have fabricated flexible electronic devices to test the strain-based change in resistance of a network of single-walled carbon nanotubes (SWCNTs) for use in microscale, high resolution magnetometry. To do this, we first develop a simple, reliable method to obtain catalyst nanoparticles for carbon nanotube growth through indirect, thin-film evaporation. Next we fabricate a two-terminal SWCNT device on a rigid substrate. We then transfer the device, intact, to a flexible substrate for strain testing. Herein, we report progress in growth and measurement techniques.
Electrochemical Sensing Properties of Ultra Long Aligned Multi-Walled Carbon Nanotube Microelectrodes
Authors: Punbusayakul Niramol , Ci Lijie , Talapatra Saikat , Surareungchai Werasak , Ajayan Pulickel M. 
Published: April 2011

ABSTRACTWe report on the electrochemical properties of ultra long aligned multiwalled carbon nanotube (MWNT) bundles synthesized using water-assisted chemical vapor deposition process. Cyclic voltammogram with diffusion-controlled-reversible reaction obtained at MWNT electrodes in 10 mM K3(Fe(CN)6) /0.1 M KCl solution with varying scan rates indicates that radial diffusion mass transport is dominant at these electrodes. We further show that these electrodes can detect very low concentrations of ascorbic acid (AA) and dopamine (DA) (0.7 μM for AA and 1.87 μM for DA ). The excellent electrochemical properties along with nice performance for single species detection suggest that these MWNTs are promising electrode materials for developing high sensitive chemical and/or biological sensors.
Electrochemical Depositon of End-Capped Triarylamine and CBP Dendrimers: Alternate Technique for the Fabrication of Organic Light-Emitting Devices
Authors: Son Ho-Jin , Han Won-Sik , Chun Ji-Yun , Wee Kyung Ryang , Kim Dae Hyun , Lee Kuk-Wha , Jung Ha Jin , Lee Chongmok , Ko Jaejung , Kang Sang Ook 
Published: April 2011

ABSTRACTCarbosilane dendrimers adorned with either triarylamine or carbazole units in their periphery exhibit novel electrochemical behavior in which the electrochemical deposition is controlled by dendrite generation. In addition, the deposited layers remained intact in the depositing solvent, methylene chloride, allowing a second layer to be deposited on top of the first layer. We have sought to establish the suitability of this electrochemical deposition technique for use in the construction of multi-layer OLEDs, which cannot be fabricated via conventional spin-coating with a polymeric precursor. Thus, the electrochemical deposition-based process could potentially offer an ideal combination of deposition control on the one hand and multi-layer fabrication on the other. We report herein the novel electrochemical deposition behavior of arylamine or carbazole end-capped carbosilane dendrimers of the type GnNPB or GnCBP (n = 1-4) and their use for the formation of multi-layer devices for OLEDs.
Rubrene Single-crystal Organic Field Effect Transistor with Laser Ablated BaTiO3 Epitaxial Growth Thin-film as High-k Insulator
Authors: Hiroshiba Nobuya , Kumashiro Ryotaro , Takenobu Taishi , Komatsu Naoya , Suto Yusuke , Iwasa Yoshihiro , Kotani Kenta , Kawayama Iwao , Tonouchi Masayoshi , Tanigaki Katsumi 
Published: April 2011

ABSTRACTHigh quality BaTiO3 thin film epitaxially grown on a Nb-doped SrTiO3 (BTO/Nb-STO) substrate by a laser ablation technique is employed as a high-k gate insulator for a field-effect transistor of a rubrene single crystal in order to search for the possibility of high carrier accumulation. The high dielectric constant of 280 esu for the prepared BaTiO3 thin film accumulates 0.1 holes/rubrene-molecule, which is 2.5 times as high as the maximum carrier number of 0.04 holes/rubrene-molecule attained in the case of SiO2 gate insulator. Important parameters of rubrene single crystal FETs on BTO/Nb- STO are also described in comparison with those on SiO2/doped-Si.
Nano-scale Conductive Films for High Performance Fine Pitch Interconnect
Authors: Li Yi , Yim Myung Jin , Moon Kyung Sik , Wong ChingPing 
Published: April 2011

ABSTRACTIn this paper, a novel nano-scale conductive film which combines the advantages of both traditional anisotropic conductive adhesives/films (ACAs/ACFs) and nonconductive adhesives/films (NCAs/NCFs) is introduced and developed for next generation high performance ultra-fine pitch packaging applications. This novel interconnect film possesses the properties of electrical conduction along the z-direction with relatively low bonding pressure (ACF-like) and the ultra-fine pitch (< 100 nm) capability (NCF-like). Unlike typical ACF which requires 1–5 vol% of conductive fillers, the novel nano-scale conductive film only needs less than 0.1 vol% conductive fillers to achieve good electrical conductance in the z direction. The nano-scale conductive film also allows a lower bonding pressure than NCF to achieve a much lower joint resistance (over two orders of magnitude lower than typical ACF joints) and higher current carrying capability. With low temperature sintering of nano-silver fillers, the joint resistance of the nano-scale conductive film could be as low as 10−5 Ohm, even lower than the NCF and lead-free solder joints. The reliability of the nano-scale conductive film after high temperature and humidity test (85°C/85%RH) was also improved compared to the NCF joints. As such, a high performance, fine pitch conductive film was developed.
NanoCT: Visualizing of internal 3D-Structures with Submicrometer Resolution
Authors: Brunke Oliver , Neuber Dirk , Lehmann David K. 
Published: April 2011

ABSTRACTHigh-resolution Computed Tomography (CT) widely expands the spectrum of detectable internal micro-structures. The new nanotom CT system allows the analysis of samples with the exceptional voxel-resolution of less than 0.5 microns per volume pixel (voxel). Thus internal detail related to a variation in material, density or porosity can be visualised and precisely measured. This opens a new dimension of 3D-microanalysis and will partially substitute traditional destructive methods in industrial quality control and research.The nanotom® is the first 180 kV nanoCT system world-wide which is tailored specifically to the highest-resolution applications in material science, micro electronics, geology and biology. Therefore it is particularly suitable for nanoCT-examinations of material samples of any type like synthetic materials, ceramics, composite materials, mineral and organic samples.Several results of high-resolution nanoCT demonstrate the capability to analyse the 3D-microstructure of materials with only minimal sample preparation. For instance, it is possible to image different metal phases in solder joints, the texture of fibres in composites or the volume and distribution of voids in castings.The volume data set is visualised by slices or compiled in a three-dimensional view which can be displayed in various ways. By means of volume visualisation software, the three-dimensional structure of the reconstructed volume can be easily analysed for pores, cracks, and materials density and distribution with the highest magnification and image quality available.By granting the user the ability to navigate the internal structure of an object slice-by-slice with highest resolution in a non-destructive manner, the nanotom creates new possibilities for analysis which have so far been unreachable.