bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density functional study of graphene overlayers on SiC
Authors: Mattausch Alexander , Pankratov Oleg 
Published: June 2008

AbstractDespite the ongoing “graphene boom” of the last three years our understanding of epitaxial graphene grown on SiC substrate is only beginning to emerge. Along with experimental methods such as low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and angle resolved photoemission spectroscopy (ARPES), ab initio calculations help to uncover the geometric and electronic structure of the graphene/SiC interface. In this chapter we describe the density‐functional calculations we performed for single and double graphene layers on Si‐ and C‐terminated 6H‐SiC surfaces. Experimental data reveal a pronounced difference between the two surface terminations. On a Si‐terminated surface the interface adopts a 6√3 × 6√3 unit cell whereas the C‐face supports misoriented (turbostratic) graphene layers. It has been recently realized that, on the Si‐face, the large commensurate cell is subdivided into patches of coherently matching to the substrate carbon atoms. In our calculations we assumed the “coherent match” geometry for the whole interface plane. This reduces the periodic unit to the √3 × √3R 30° cell but requires a substantial stretching of the graphene sheet. Although simplified, the model provides a qualitative picture of the bonding and of the interface electron energy spectrum. We find that the covalent bonding between the carbon layer and the substrate destroys the massless “relativistic” electron energy spectrum, the hallmark of a freestanding graphene. Hence the first carbon layer cannot be responsible for the graphene‐type electron spectrum observed by ARPES and rather plays a role of a buffer between the substrate and the subsequent carbon sheets. The “true” graphene spectrum appears with the second carbon layer which exhibits a weak van der Waals bonding to the underlying structure. For Si‐terminated substrate, we find that the Fermi level is pinned by the interface state at 0.45 eV above the graphene Dirac point, in agreement with experimental data. This renders the interface metallic. On the contrary, for a C‐face the “coherent match” model predicts the Fermi level exactly at the Dirac point. However, this does not necessarily apply to the turbostratic graphene layers that normally grow on the C‐terminated substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of intrinsic defects in SiC: Towards an understanding of defect aggregates by combining theoretical and experimental approaches
Authors: Bockstedte Michel , Gali Adam , Mattausch Alexander , Pankratov Oleg , Steeds John W. 
Published: June 2008

AbstractIn SiC, mobile point defects may form thermally stable clusters and aggregates, such as di‐vacancies or carbon interstitial complexes. Although predicted by theory, experimental evidence of such clusters became available only recently. Combining theoretical and experimental approaches, the unique identification of the di‐vacancy, the carbon vacancy‐antisite complex with the spin resonance centers P6/P7 and SI5 was recently achieved. In this way also the di‐carbon and tri‐carbon antisites with the photoluminiscence centers P–T and U, HT3 and HT4, respectively were identified. The two identified vacancy complexes show distinct properties: while the di‐vacancy, like the silicon vacancy possesses a high‐spin ground state, the carbon vacancy–antisite complex, like the carbon vacancy, is a Jahn–Teller center. These effects consistently explain the complex properties of the spin resonance spectra and are discussed in detail for the isolated vacancies. The aggregation of vacancies proved to be relevant in the explantation of the kinetic deactivation of nitrogen in co‐implanted SiC. This and further evidence for defect aggregates underline the relevance of this notion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Present status and future prospects for electronics in electric vehicles/hybrid electric vehicles and expectations for wide‐bandgap semiconductor devices
Authors: Hamada Kimimori 
Published: June 2008

AbstractToyota refers to the ability of users to continuously enjoy the convenience provided by automobiles as ‘sustainable mobility’. In order to achieve this, we are carrying out the endless challenge of minimizing the negative aspects of automobiles, such as CO2emissions, air pollution, traffic fatalities, and congestion, while maximizing automobile comfort, enjoyment, and excitement. In the area of the environment, we believe that we can come closer to creating the ‘ultimate ecovehicle’ by increasing the environmental performance of the power train, utilizing new fuels and electrical energy, and integrating hybrid technology into all of the results. In the Toyota Group, we think that power electronics is a key technology for the automotive technology of the future. We have defined SiC and GaN as core items for breakthroughs in power electronics technologies for the future, and we are energetically pursuing research and development in those areas. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of an intermediate graphite layer on the electronic properties of metal/SiC contacts
Authors: Reshanov Sergey A. , Emtsev Konstantin V. , Speck Florian , Gao Kun‐Yuan , Seyller Thomas K. , Pensl Gerhard , Ley Lothar 
Published: June 2008

AbstractPhotoelectron spectroscopy and electrical measurements were used to study the graphite/SiC‐interface with emphasis on the Schottky barrier formation. The investigations revealed a strong dependence of the Schottky barrier height on the surface polarity of SiC. In the case that the graphite layer was prepared on the Si(0001)‐face of n‐/p‐type 4H‐ and n‐/p‐type 6H‐SiC, the Fermi level is pinned close to the conduction band edge at the interface. The Schottky barrier fabricated on n‐type 4H‐SiC (0001) is 0.6 eV, whereas on n‐type 6H‐SiC (0001) it is lower and amounts (0.3–0.55) eV. On p‐type 4H‐/6H‐SiC, the Schottky barrier is 2.6 eV and (2.3–2.7) eV, respectively. When the Schottky barrier is prepared on the C‐face (000$ \bar 1 $) of n‐type 6H‐SiC, the Fermi level is pinned close to the middle of the band gap. In this case, the Schottky barrier height is found to be equal to 1.4 eV. It is demonstrated that the carbon/graphite formation at the interface between metal and n‐type 4H‐SiC does not ensure ohmic behavior. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐ and nanomechanical structures for silicon carbide MEMS and NEMS
Authors: Zorman Christian A. , Parro Rocco J. 
Published: June 2008

AbstractSilicon carbide (SiC) is recognized as the leading semiconductor for high power and high temperature electronics owing to its outstanding electrical properties combined with mature processing technologies for monolithic structures. SiC has long been known for its outstanding mechanical and chemical properties making it equally attractive for mechanical structures in micro‐ and nanoelectromechanical systems (MEMS and NEMS). Recent advancements in bulk and surface micromachining have led to the development of SiC analogues to common Si‐based devices (i.e., resonators, pressure sensors). This paper presents an overview of MEMS and NEMS technologies that incorporate SiC as a key component in their mechanical structure, providing both a historical perspective as well as recent developments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial graphene: a new material
Authors: Seyller Th. , Bostwick A. , Emtsev K. V. , Horn K. , Ley L. , McChesney J. L. , Ohta T. , Riley J. D. , Rotenberg E. , Speck F. 
Published: June 2008

AbstractGraphene, a two‐dimensional sheet of sp2‐bonded carbon arranged in a honeycomb lattice, is not only the building block of fullerenes, carbon nano tubes (CNTs) and graphite, it also has interesting properties, which have caused a flood of activities in the past few years. The possibility to grow graphitic films with thicknesses down to a single graphene layer epitaxially on SiC{0001} surfaces is promising for future applications. The two‐dimensional nature of epitaxial graphene films make them ideal objects for surface science techniques such as photoelectron spectroscopy, low‐energy electron diffraction, and scanning probe microscopy. The present article summarizes results from recent photoemission studies covering a variety of aspects such as the growth of epitaxial graphene and few layer graphene, the electronic and structural properties of the interface to the SiC substrate, and the electronic structure of the epitaxial graphene stacks. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface morphology and growth mechanism of catalyst‐free ZnO and Mgx Zn1–xO nanorods
Authors: Kim Miyoung , Hong Young Joon , Yoo Jinkyoung , Yi Gyu‐Chul , Park Gyeong‐Su , Kong Ki‐jeong , Chang Hyunju 
Published: June 2008

AbstractHigh‐resolution transmission electron microscopy was employed to investigate morphologies and catalyst‐free growth mechanism of ZnO/Mgx Zn1–x O ‘multi‐quantum well’ and ‘core‐shell’ nanorod heterostructures as well as ZnO nanorods. The one‐dimensional growth mechanism and the hexagonal faceting of ZnO nanorod were explained by the surface energy anisotropy. The morphology change by alloying with Mg was successfully explained by investigating the energy gain by adatom adsorption and the reduction in the surface energy anisotropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of polar organophosphorus pesticides in water samples by hydrophilic interaction liquid chromatography with tandem mass spectrometry
Authors: Hayama Tadashi , Yoshida Hideyuki , Todoroki Kenichiro , Nohta Hitoshi , Yamaguchi Masatoshi 
Published: June 2008

AbstractA method combining hydrophilic interaction liquid chromatography (HILIC) with tandem mass spectrometry (MS/MS) was developed for the determination of polar organophosphorus pesticides (OPPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton‐methyl, and vamidothion) in water samples. To extract the polar OPPs and minimize matrix effects from the water sample, an activated carbon cartridge was used for pretreatment. After pretreatment of the water sample, the eluate from the activated carbon cartridge was directly injected into the HILIC/MS/MS system. The OPPs were separated on an Atlantis HILIC silica column by isocratic elution with a mixture of acetonitrile, isopropanol, and ammonium formate buffer as a mobile phase, and they were detected by positive electrospray ionization MS/MS in the selected reaction monitoring mode. The method was validated at 0.05, 0.5, and 5 µg/L levels in water samples, and the recoveries of polar OPPs were between 76.4 and 98.6%. The limits of detection were between 0.13 and 1.0 pg on‐column, and the limits of quantification were between 0.43 and 3.4 pg on‐column. The method can be applied to the determination of trace amounts of OPPs in environmental water samples. Copyright © 2008 John Wiley & Sons, Ltd.
Identification of low molecular weight carbohydrates employing new binary mixtures for matrix‐assisted laser desorption/ionisation mass spectrometry
Authors: Hashir Muhammad Ahsan , Stecher Guenther , Bonn Guenther K. 
Published: June 2008

AbstractVarious energy‐absorbing substances, aminopyrazine (AP), 4,4'‐azodianiline (ADA), and 1‐chloro‐4‐hydroxyisoquinoline (CHIQ), together with their binary mixtures with existing acidic MALDI matrices were subjected to matrix‐assisted laser desorption/ionisation mass spectrometry (MALDI‐MS) and evaluated for the analysis of low molecular weight carbohydrates. The newly introduced systems, especially AP and the combination of 2,5‐dihydroxybenzoic acid and aminopyrazine (DHB‐AP), have solved almost all the existing problems of the generally low sensitivity of carbohydrate analysis and of the strong background noise produced from single acidic matrices. In fact, especially at a mixing ratio of 3:1 (DHB/AP), outstanding results could be achieved, enabling the detection of analytes down to a concentration of 4 fmol/µL with mass accuracy of 37 ppm. The performance of the system was finally proven by analysing dextrins and biological samples each of which showed excellent signal intensity and signal‐to‐noise ratio. Copyright © 2008 John Wiley & Sons, Ltd.
Dynamic resource allocation for DVB‐RCS networks
Authors: Petraki Dionysia K. , Anastasopoulos Markos P. , Cottis Panayotis G. 
Published: June 2008

AbstractTo provide high‐speed multimedia services using the digital video broadcasting‐return channel satellite (DVB‐RCS) standard, it is imperative to efficiently assign timeslots according to user demands and dynamically take into account the variations of the propagation conditions. In satellite networks operating above 10 GHz, rain fading constitutes the dominant factor deteriorating the quality of service. In this paper, a novel two‐phase resource allocation scheme for a DVB‐RCS compliant satellite network is proposed. The scheme operates in two phases, the resource calculation and the resource assignment. In the resource calculation phase, based on a dynamic channel model, an efficient algorithm is presented to determine the superframe design that maximizes system throughput. In the resource assignment phase, a novel Hybrid Bin‐packing algorithm is introduced maximizing the utilization of the multi‐frequency time division multiple access frame. The proposed algorithm has been compared with existing schemes exhibiting significantly better results with regard to overall system throughput. Copyright © 2008 John Wiley & Sons, Ltd.
Two Three‐Dimensional Metal‐Organic Frameworks Constructed from Alkaline Earth Metal Cations (Sr and Ba) and 5‐Nitroisophthalicacid – Synthesis, Charaterization, and Thermochemistry
Authors: Chen Sanping , Shuai Qi , Gao Shengli 
Published: June 2008

AbstractTwo MOFs of [SrII(5‐NO2‐BDC)(H2O)6] (1) and [BaII(5‐NO2‐BDC)(H2O)6] (2) have been synthesized in water using alkaline earth metal salts and the rigid organic ligand 5‐NO2‐H2BDC. The compounds were characterized by elemental analysis, infrared spectrum, thermal analysis, and X‐ray crystallography. Crystal structure analyses have shown that the two complexes are isostructural as evidenced by IR spectra and TG‐DTA. Both compounds present three‐dimensional frameworks built up from infinite chains of edge‐sharing twelve‐membered rings through O–H···O hydrogen bonds. The specific heat capacities of the title complexes have been determined by an improved RD496‐III microcalorimeter with the values of (109.29 ± 0.693) J mol−1 K−1 and (81.162 ± 0.858) J mol−1 K−1 at 298.15 K, and the molar enthalpy changes of the formation reactions of complexes at 298.15 K were calculated as (4.897 ± 0.008) kJ mol−1 and (2.617 ± 0.009) kJ mol−1, respectively.
Polysulfonylamine. CLXXXIV. Kristallstrukturen molekularer Triphenylphosphangold(I)‐di(4‐X‐benzolsulfonyl)‐amide: Isomorphie und dichte Packung (X = Me, F, Cl, NO2) vs. struktursteuernde Halogenbrücken C–X···Au/O (X = Br, I)
Authors: Wölper Christoph , Roca Piñol Silvia , Durán Ibáñez Sara , Freytag Matthias , Jones Peter G. , Blaschette Armand 
Published: June 2008

AbstractPolysulfonylamines. CLXXXIV. Crystal Structures of Molecular Triphenylphosphanegold(I) Di(4‐X‐benzenesulfonyl)amides: Isomorphism and Close Packing (X = Me, F, Cl, NO2) vs. Structure‐Determining C–X···Au/O Halogen Bonds (X = Br, I)In order to study the structure‐determining influence that halogen bonding can exert during the course of crystallization, solid‐state structures are compared for two previously reported and four new molecular gold(I) complexes of the type Ph3P–Au–N(SO2–C6H4–4‐X)2, each featuring linear P,N coordination at gold and two phenyl rings with varying p‐substituents X = Me, F, Cl, NO2, Br or I. The compounds were synthesized by reactions of Ph3PAuX (X = Cl or I) with the corresponding silver di(arenesulfonyl)amides, crystallized from dichloromethane, and characterized by low‐temperature X‐ray diffraction. The Me, F, Cl and NO2 congeners are isomorphic and crystallize without solvent inclusion in the chiral orthorhombic space group P212121 (Z′ = 1). These structures are governed by isotropic close packing via three‐dimensional 21 symmetry, incidentally supported by an invariant set of C–H···O=S hydrogen bonds, CH/π interactions and π/π stackings of aromatic rings; in particular, the hard halogen atoms of the fluoro and the chloro homologues are not involved in X···Au, X···O or X···X interactions. The higher homologues, with soft halogen atoms, were obtained as a dichloromethane hemisolvate for X = Br and a corresponding monosolvate for X = I, each triclinic in the centrosymmetric space group $P{\bar 1}$ (Z′ = 1). Here, the primary structural effect is implemented by infinite chains in which translation‐related molecules are connected for the bromo compound by a bifurcated Au···Br(2)···O=S interaction, for the iodo congener by an equivalent Au···I(2)···O=S interaction and a short halogen bond C–I(1)···O=S. The latter bond is stronger than a similar C–Br···O=S interaction and induces a conformational adjustment of the (CSO2)2N group from the normal twofold symmetry in the bromo compound to an energetically unfavourable asymmetric form in the iodo homologue. In both cases, pairs of antiparallel molecular catemers are associated into strands via sixfold phenyl embraces, the strands are stacked to form layers, the solvent molecules are intercalated between adjacent layers, and the crystal packings are reinforced by a number of C–H···O=S hydrogen bonds and interactions of aromatic rings.
Crystal Structure of Ammonium Catena‐polyphosphate IV [NH4PO3]x
Authors: Sedlmaier Stefan J. , Schnick Wolfgang 
Published: June 2008

AbstractPhase‐pure ammonium catena‐polyphosphate IV [NH4PO3]x was synthesized by heating NH4H2PO4 in a tube furnace under an ammonia gas flow. The product contained single crystals of [NH4PO3]x IV appropriate for an X‐ray structure determination enabling structure refinement of this compound. The pseudo‐merohedrally twinned crystals of [NH4PO3]x crystallize in the monoclinic crystal system (P21/c, no. 14, a = 2270.3(5), b = 458.14(9), c = 1445.1(3) pm, β = 108.56(3)°, Z = 4, 2264 data, R1 = 0.076). In the unit cell the catena‐polyphosphate chain anions run parallel [010] with a chain‐periodicity P = 2 and a stretching factor fs = 0.94. The chain anions are interconnected through extensive hydrogen bonding towards the ammonium ions. Due to ‘chemical twinning’ a novel catena‐polyphosphate structure type is realized in [NH4PO3]x IV. The vibrational spectra of [NH4PO3]x IV are reported as well.
Synthesis and X‐ray Crystal Structures of Acenaphthenequinone‐based α‐Diimine Palladium Complexes and a Novel V‐shape Tripalladium Cluster
Authors: Zhou Jin , Sun Hongjian , Harms Klaus , Sundermeyer Jörg 
Published: June 2008

AbstractPartially fluorinated 1,4‐Diazadiene (α‐Diimine) ligand 3,5‐CF3‐BIAN (1) formed from 3,5‐bis(trifluoromethyl)aniline and acenaphthenequinone was used in the synthesis of palladium dichlorido complex 2 and its mono methyl chlorido palladium complex 3. Both complexes as well as side products of the reaction with methyl lithium such as trans‐bis(3,5‐bis(trifluoromethyl)aniline complex 4 and an interesting mixed valent trinuclear V‐shaped palladium cluster 5 with two bridging μ2,η3‐N,CN′ non‐innocent BIAN ligands were structurally characterized by the single‐crystal XRD method.
Earth Alkaline Tetrathiosquarates. II. – Syntheses and Crystal Structures of SrC4S4·4 H2O and Ba4K2(C4S4)5·16 H2O
Authors: Beck Johannes , Ben‐Amer Younis 
Published: June 2008

AbstractConcentrated aqueous solutions of strontium chloride and barium chloride, respectively, allow on addition of the potassium salt of tetrathiosquarate, K2C4S4·H2O, the isolation of the earth alkaline salts SrC4S4·4 H2O (1) and Ba4K2(C4S4)5·16 H2O (2), both as dark red crystals. The crystal structure determinations (1: orthorhombic, Pnma, a = 8.149(1), b = 12.907(2), c = 10.790(2) Å, Z = 4; 2: orthorhombic, Pbca, a = 15.875(3), b = 21.325(5), c = 16.119(1) Å, Z = 4) show the presence of C4S42− ions with only slightly distorted D4h symmetry having average C–C and C–S bond lengths of 1.41Å and 1.681Å for 1 and 1.450Å and 1.657Å for 2. The structure of 1 contains concatenated edge‐sharing Sr(H2O)6S2 polyhedra. The Sr2+ ions are in eight‐fold coordination with Sr–O distances of 2.50–2.72Å and Sr–S distances of 3.21Å, (C4S4)2− acts as a chelating ligand towards Sr2+. The structure is closely related to the previously reported Ca2+ containing analogue, which is of lower symmetry belonging to the monoclinic crystal system. A supergroup‐subgroup relation between the space groups of both structures is present. The structure of 2 is made up of Ba2+ and K+ ions in eight and nine‐fold coordination by H2O molecules and (C4S4)2− ions which act as chelating ligands towards one cation and bridging between two cations. The coordination polyhedra of the cations are connected by common edges and corners in two dimensions to layers which are connected by tetrathiosquarate ions to a three‐dimensional network. The infrared and Raman spectra show bands typical for the molecular building units of the two compounds.
Hydrothermal Synthesis and X‐ray Crystal Structure of Four Inorganic‐Organic Hybrid Compounds in Vanadium /Copper Iodate Family
Authors: Liu Xiaomin , Li Guanghua , Bi Minghui , Hu Yawei , Yu Yang , Shi Zhan , Feng Shouhua 
Published: June 2008

AbstractFour inorganic‐organic hybrid compounds with the formulae (1,10‐phen)(VO2)(IO3) (1), (2,2′‐bipy)(VO2)(IO3) (2), [Cu3(2,2′‐bipy)3Cl3(IO3)2]·I1.5 (3), and [Cu(2,2′‐bipy)(H2O)(IO3)2]· (H2O)2 (4) are hydrothermally synthesized at 120 °C for 6 d and characterized by single‐crystal X‐ray diffraction. The use of two different bidentate organodiamine ligands 1,10‐phen and 2,2′‐bipy in the V/I/O system gives rise to compounds 1 and 2, which crystallize in a monoclinic system with the space group C2/c, a = 17.8131(6) Å, b = 15.0470(7) Å, c = 12.9902(4) Å, β = 133.095(2)°, V = 2542.49(17) Å3 for 1 and space group P21/c, a = 13.3095(5) Å, b = 15.0993(8) Å, c = 13.0454(4) Å, β = 116.971(2)°, V = 2335.88(17) Å3 for 2. The use of the bidentate organodiamine ligand 2,2′‐bipy in the Cu/I/O system gives rise to the variety in the structure of products 3 and 4, which crystallize in a triclinic system with the same space group $P{\bar 1}$. a = 8.5143(2) Å, b = 10.4908(3) Å, c = 22.8420(6) Å, α = 93.769(10)°, β = 91.723(10)°, γ = 112.111(10)°, V = 1882.83(9) Å3 for 3 and a = 6.731(6) Å, b = 10.110(4) Å, c = 12.899(6) Å, α = 106.00(5)°, β = 95.45(4)°, γ = 107.69(6)°, V = 788.4(9) Å3 for 4. The solid‐state structures of the compounds 1 and 2 have chains with repeat units of alternative corner sharing of [VO4N2] octahedra and [IO3] pyramids. Compound 3 is a chain containing [IO3] pyramids and [VO4N] square pyramids and compound 4 consists of Cu(2,2′‐bipy)2+ linked by one water molecule and two [IO3] pyramids. The thermal stabilities of the compounds are investigated.
Synthesis, Structure, Spectral and Magnetic Properties of 1D Zig‐zag Coordination Complex: {[Ni(cyclam)(μ‐1,5‐dca)]ClO4·[(CH3)2CO]}n
Authors: Liu Hui , Tian Jin‐Lei , Kou Ying‐Ying , Gu Wen , Feng Li , Yan Shi‐Ping , Liao Dai‐Zheng 
Published: June 2008

AbstractA new nickel(II) complex, {[Ni(cyclam)(μ‐1,5‐dca)]ClO4·[(CH3)2CO]}n (1), (cyclam = 1, 4, 8, 11‐tetraazacyclotetradecane, dca = dicyanamide, N(CN)2−) has been synthesized and structurally characterized. The complex crystallizes in orthorhombic system, space group Pnma; with a = 9.1958(15) Å, b = 15.528(3) Å, c = 16.335(3) Å and Z = 4. According to X‐ray crystallographic studies, 1 is a one‐dimensional zig‐zag infinite chain complex which consists of alternately single μ‐1,5‐dca linked the nickel atoms. The IR and UV spectroscopy were measured. The absorption bands of d–d electron transition are assigned and the values of Dq and B were calculated according to the electronic spectrum of the complex. The magnetic property studies indicate that complex 1 exhibits weak antiferromagnetic interaction through the five‐atom [NCNCN] bridging ligands with J = –0.382 cm−1.