bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bifunctional‐Thiourea‐Catalyzed Diastereo‐ and Enantioselective Aza‐Henry Reaction
Authors: Xu Xuenong , Furukawa Tomihiro , Okino Tomotaka , Miyabe Hideto , Takemoto Yoshiji 
Published: September 2005

AbstractBifunctional thiourea 1 a catalyzes aza‐Henry reaction of nitroalkanes with N‐Boc‐imines to give syn‐β‐nitroamines with good to high diastereo‐ and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N‐protecting groups of the imines have a determining effect on the chirality of the products, that is, the reaction of N‐Boc‐imines gives R adducts as major products, whereas the same reaction of N‐phosphonoylimines furnishes the corresponding S adducts. Various types of nitroalkanes bearing aryl, alcohol, ether, and ester groups can be used as nucleophiles, providing access to a wide range of useful chiral building blocks in good yield and high enantiomeric excess. Synthetic versatility of the addition products is demonstrated by the transformation to chiral piperidine derivatives such as CP‐99,994.
Growth of tin oxide nanocrystals
Authors: Zanotti L. , Zha M. , Calestani D. , Comini E. , Sberveglieri G. 
Published: September 2005

AbstractFunctional oxides are presently much investigated as regards not only their basic properties, but also their actual and potential applications. Tin oxides appear particularly interesting when grown in nanowire shape (SnO2‐NW) because of their electronic‐ and sensor‐device applications. In this paper the results of a systematic study on nucleation and growth of SnO2‐NWs, when an open‐tube vapor‐transport technique is employed, are reported and discussed. The vapor transport conditions have been investigated in greater detail and for the first time a growth model is proposed. Functional tests at different temperatures and gaseous compositions have proved that the SnO2‐NW are suitable for the preparation of highly‐sensitive and stable gas sensors. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Morphological, structural and optical study of quasi‐1D SnO2 nanowires and nanobelts
Authors: Calestani D. , Lazzarini L. , Salviati G. , Zha M. 
Published: September 2005

Abstract0.1–0.3 mm thick entanglements of quasi‐one‐dimensional semiconducting Tin dioxide nanocrystals, in form of nanowires and nanobelts, are successfully grown by low cost Chemical Vapour Deposition directly on large area (100 mm2) Al2O3, SiO2 and Si substrates. Their lateral size ranges from 50 to 700 nm and their length can achieve several hundreds of micrometers. Transmission Electron Microscopy reveals either the nanowires and the nanobelts grow in the tetragonal Rutile structure. Diffraction contrast analyses and selected area diffraction investigations show the nanowires are single crystals without defects while the nanobelts sometimes present twins inside. An almost cylindrical shape and an average diameter of about 30–50 nm for the smallest nanowires is reported. X‐ray diffraction investigations exclude the presence of spurious phases. A broad band structured in two emissions peaked at about 450 nm and 560 nm is revealed by large area Cathotoluminescence, while single nanocrystal spectroscopy shows that the reduction of the lateral dimension of the nanobelts from 1000 nm to 50 nm blue‐shifts the main emission band at 560 nm of about 40 nm (at room temperature). These preliminary results suggest a possible role of oxygen vacancies and of the surface/volume ratio on the origin and the blue shift of Cathodoluminescence spectra. The near band edge emission, typical of bulk tin dioxide (∼320 nm), is not found in nanobelts narrower than 1000 nm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spontaneous ordering of self‐assembled‐Ge island
Authors: De Seta M. , Capellini G. , Evangelisti F. 
Published: September 2005

AbstractSelf‐assembled quantum dots can be the building blocks of a variety of mesoscopic devices. However, in order to use these structures in large‐scale integrated devices, accurate control over their spatial positioning is required. We show here that, by a suitable engineering of the deposition process, it is possible to obtain self‐organization resulting in well ordered clusters composed of regularly disposed nano‐sized islands. Elastically relaxed Ge islands act as a stressor for a Si layer subsequently deposited (Ge has a 4% larger lattice cell). This effect results in a modulation of the lattice parameter and strain field in the Si over‐layer. In particular the Si lattice in the columnar region on top of the buried islands is tensile strained and will act as preferential nucleation site for the subsequent Ge island growth. We have generated a square array of tensile‐strained regions oriented along the [010]‐[100] directions on the Si(001) surface exploiting the self‐ordering occurring in the growth at 750 °C of Ge island multi‐layers used as a template. The strain field intensity and shape was modified by changing the thickness of the template Si over‐layer: the thicker the overlayer the wider and less intense the strain field in the Si tensile regions. On this template we have grown a Ge island layer at the lower temperature of 600 °C. At this growth temperature the islands are much smaller than the lateral extension of the strain field on the Si surface of the template and the nucleation and evolution of several islands inside a single tensile‐strained regions is promoted. Upon decreasing the template Si over‐layer thickness from 200 to 35 nm the Ge island spatial distribution changes from random to a well‐ordered square lattice of multi‐island clusters. At intermediate Si over‐layer thickness (65 nm), the Ge islands are confined in cluster regions only at the first stage of their evolution (pyramids), while for thinner over‐layer (35 nm) islands are assembled in clusters up to the last stage their growth dynamics (relaxed domes). The strong dome‐to‐dome interaction within a cluster, due to their small mutual separation, has impact also on the dome size by reducing their mean base width of about 35%. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of II‐VI nanocrystals in polymeric matrix: Thermolytic synthesis and structural characterization
Authors: Antolini F. , Di Luccio T. , Re M. , Tapfer L. 
Published: September 2005

AbstractIn this work we report on the growth of CdS and ZnS semiconductor nanocrystals embedded in a polymeric matrix (polystyrene) by synthesizing a metal thiolate precursor and its subsequent thermolysis at about 300 °C after dispersion in the polymer. The crystallinity, shape and size of the metal sulfide nanocrystals were investigated by x‐ray diffraction and transmission electron microscopy. The microstructural analysis demonstrates that our synthesis procedure allows us to control the nanocrystal growth in order to form nanoparticles with diameter as small as Ø = 2 nm. In particular, XRD analysis reveals that only CdS and ZnS nanocrystals of zincblende structure are formed. TEM images show that the metal sulfide nanocrystals are monocrystals of spherical shape and the size dispersion is <20%. Our experiments indicate that the nanocrystal capping agent is performed by the sulfur atoms at the surface of the nanoparticle bound to alkyl chain of the thiolate. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth, morphological and structural characterization of silicon carbide epilayers for power electronic devices applications
Authors: Pirri C. F. , Porro S. , Ferrero S. , Celasco E. , Guastella S. , Scaltrito L. , Yakimova R. , Syväjärvi M. , Ciechonski R. R. , De Angelis S. , Crippa D. 
Published: September 2005

AbstractSilicon carbide (SiC) is a wide band gap semiconductor, interesting for its physical properties such as high breakdown field, high saturated drift velocity and high thermal conductivity, which has been intensively studied in the last years. Although the high potentiality of this material, the SiC technology shows at the moment some limitations, indeed, the reliability of SiC‐based devices is strictly correlated to the defects present in the crystalline structure. 4H‐SiC epilayers were grown by Hot Wall Chemical Vapor Deposition (at 1600 °C) and by Sublimation techniques (at 2000 °C). A surface investigation of the epilayers has been performed finding particular physical finger‐prints correlated with several kind of defects aimed at giving an important feedback to the epitaxial growth processes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Horizontal hot wall reactor design for epi‐SiC growth
Authors: Veneroni A. , Omarini F. , Masi M. , Leone S. , Mauceri M. , Pistone G. , Abbondanza G. 
Published: September 2005

AbstractThe model adopted for the simulation of a new industrial size type of horizontal cold wall reactor for epitaxial silicon carbide deposition is reviewed. The attention is focalized on the chemical mechanism adopted and on the comparison with some growth rate data and temperature profiles for the system ethylene, silane, hydrogen and the deposition of undoped silicon carbide. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamical analysis of abrupt interfaces of InGaP/GaAs and GaAs/InGaP heterostructures
Authors: Pelosi C. , Attolini G. , Bosi M. , Frigeri C. , Bersani M. , Giubertoni D. , Vanzetti L. , Musayeva N. 
Published: September 2005

AbstractInterfaces between arsenide and phosphide III‐V semiconductors have shown to be one of the most difficult issues to be understood and definitively solved. This problem is particularly relevant with Vapour Phase Epitaxy (VPE) and Metallo‐Organic Vapour Phase Epitaxy (MOVPE) techniques, since an irreproducibility in preparing abrupt interfaces between arsenide and phosphide has been evidenced. Several researchers have ascribed this problem to the volatility of arsenic and phosphorus species and since then for long time different recipes and growth procedures have been suggested in order to obtain sharp transition between the two different materials. In this work the film/substrate interface is modelled using thermodynamical calculations after the regular solution model proposed by Jordan and Ilegems: PH3 flows over GaAs surface, and as a consequence the substrate is enriched with P, with the formation of a thin layer of GaAsP and mixed As‐P gaseous species. Samples of InGaP on GaAs substrate were grown by MOVPE and characterised by Secondary Ion Mass Spectroscopy (SIMS) and Transmission Electron Microscopy (TEM) in order to support the theoretical findings. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homoepitaxy of ZnTe on (100) oriented substrates: Technology issues and MOVPE growth aspects
Authors: Traversa M. , Lovergine N. , Prete P. , Tapfer L. , Mancini A. M. 
Published: September 2005

AbstractThe metalorganic vapour phase epitaxy of ZnTe on single crystal (100)ZnTe:P wafers is reported. The technological steps to prepare a substrate surface suitable for the high quality homoepitaxy of ZnTe are identified and optimised in terms of structural and morphological properties of overgrown epilayers. Removal of ∼7 µm of material from the ZnTe:P wafers by chemical etching in 1% Br2‐methanol solution proved necessary to achieve a sufficiently smooth and homogeneous surface; in‐situ H2 heat treatment of the wafers at 350°C immediately before growth ensures optimal desorption of residual oxides, allowing epilayer crystalline quality comparable to the substrate. However, the structure of epilayers degrades for growth temperatures (TG) above 350 °C due to the occurrence of stacking faults (SFs) within ∼200‐300 nm from the epilayer‐substrate interface. Accordingly, the epilayer band‐edge luminescence vanishes below 350 nm, indicating a worsening of the material radiative efficiency in very thin epilayers. The epilayer surface morphology is the result of a complex interplay between SF nucleation and Te:Zn ad‐atom stoichiometry during growth. Almost featureless morphologies are obtained for growth at 350 °C, i.e. under nearly stoichiometric surface conditions. Pyramid‐like hillocks develop instead for TG ≥ 360 °C, corresponding to Te‐rich surface conditions, their density rapidly increasing up to around 9 × 106 cm–2 at TG = 400 °C. Hillocks occur in close pairs on the epilayer surface, their nucleation being strongly reduced if a thin ZnTe buffer layer is grown at low (325 °C) temperature, i.e. if SFs do not occur at the epilayer‐substrate interface. This demonstrates that hillocks form as a result of three‐dimensional growth around partial dislocations pairs bounding SFs, the phenomenon being driven by Te ad‐atoms experiencing a Schwoebel potential barrier at the surface step edges around the dislocations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical and photoelectrical properties of a GaAs‐based p‐i‐n structure grown by MOVPE
Authors: Begotti M. , Longo M. , Magnanini R. , Tarricone L. , Gombia E. , Mosca R. , Lynch M. , Barnham K. , Mazzer M. , Hill G. 
Published: September 2005

AbstractA GaAs‐based p‐i‐n junction grown by MOVPE and using the high purity and low dissociation temperature tertiarybutylarsine (TBAs) precursor, was studied. Such a structure is suitable to play the role of a sub‐cell in a multi‐junction photovoltaic device. Electrical measurements showed excellent properties of the junction; in particular, the forward current‐voltage characteristic was detected over ten orders of magnitude, showing: a rectification ratio of about 1010 at 1.2 V, low reverse current and low series resistance. Capacitance measurements confirmed the low contaminant concentration of the unintentionally doped intrinsic region (of the order of 1014 cm–3). A fill factor equal to 0.81, confirming low background doping and indicating low series resistance, has been measured for the illuminated junction. The long wavelength tail of the spectral response, controlled by the diffusion length of the minority carriers (holes) in the n‐type base region of the junction, has been fitted, giving a hole diffusion length equal to 2 µm. The comparison with an identical structure, grown by MOVPE with the use of the traditional arsine precursor, showed that the p‐i‐n junction here studied has some superior electrical and photoelectrical properties, in particular a lower dark‐current. Although the primary use for devices of this kind is as a part of a more complex heterostructure, the p‐i‐n junction studied in this work also achieves a good projected conversion efficiency as a single junction cell (21.4 ± 1)% at AM1.5g. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth aspects of AlGaAs/GaAs tunnel diodes for multijunction solar cells
Authors: Timò G. , Flores C. , Campesato R. 
Published: September 2005

AbstractGrowth aspects related to AlGaAs/GaAs tunnel diodes for multijunction solar cell structures are presented. Test structures have been grown in order to show the correct way for checking the thermal resistance of tunnel diodes. AlGaAs:C lattice contraction as a function of carbon concentration and growth temperature has been studied by using XRD, Hall and Room temperature photoluminescence characterisation. The XRD experimental results have been successfully compared with the lattice contraction model reported by W.E Hoke et al. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Why CuInGaSe2 and CdTe polycrystalline thin film solar cells are more efficient than the corresponding single crystal?
Authors: Bosio A. , Romeo N. , Podestà A. , Mazzamuto S. , Canevari V. 
Published: September 2005

AbstractRecently, very high conversion efficiencies in thin film polycrystalline solar cells have been reported. In particular it was reached an efficiency record both for CuInGaSe2 (CIGS) and CdTe that are 19.2% and 16.5% respectively. We will briefly describe the technological methods used to fabricate these thin film solar cells. Besides, we will try to explain the reason why thin film polycrystalline devices can achieve conversion efficiency comparable with those shown by single crystal solar cells (mono‐Si or poly‐Si). We will take into consideration the tricks present in both the methods that allow to make the CIGS/CdS and CdTe/CdS thin film solar cells with excellent performances. We will show also, that these technologies are ripe for an “inline” industrial production and this makes thin film solar cells the best candidates for the large scale utilisation of photovoltaic energy conversion. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact of antimony doping on microdefect formation in Czochralski grown silicon crystals
Authors: Porrini M. 
Published: September 2005

AbstractThe impact of antimony doping on the formation of vacancy‐ and interstitial‐type microdefects in Czochralski silicon is studied by growing test crystals with different Sb doping levels, in the range from 0 (undoped) to 3 × 1018 cm–3, and with different pulling rates. Antimony is found to cause a shift from interstitial‐ to vacancy‐type microdefects, observable already at a concentration of ≈1017 cm–3. The shift coefficient K for antimony is estimated to be 7.2 × 10–19 cm3. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal growth and structural refinement of NaMn7O12
Authors: Gilioli E. , Licci F. , Calestani G. , Prodi A. , Gauzzi A. , Salviati G. 
Published: September 2005

AbstractWe report the crystal growth and the structural refinement of NaMn7O12, a manganite having a double perovskite structure. As in many similar compounds, there is coexistence of Mn3+ and Mn4+ but in this material they orderly occupy different sites for crystallographic reasons. Therefore, this peculiar structure can be considered as a model system for studying complex mechanisms such as charge, orbital and spin ordering. High purity bulk samples and “large” single crystals are needed to study tiny modifications in the crystallographic and magnetic structures associated to the ordering phenomena. Almost single phase (more than 96% pure) and single crystals (up to about 150 µm) of NaMn7O12 were synthesized by solid state reaction under pressure in a multi‐anvil apparatus. Single crystal x‐ray diffraction and SEM analysis have been used to characterize the crystals. The structure refinement indicates that NaMn7O12 crystallizes in the cubic Im3 space group, with a = 7.312 Å and Z = 2. Further studies are in progress to optimize the synthesis conditions, in order to grow larger crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth kinetics, adsorption and morphology of sucrose crystals from aqueous solutions in the presence of raffinose
Authors: Sgualdino G. , Aquilano D. , Fioravanti R. , Vaccari G. , Pastero L. 
Published: September 2005

AbstractExperimental growth kinetics of the most important F forms of sucrose crystal, {100}, {110}, {10$ \bar 1 $} and {$ \bar 1 $$ \bar 1 $0}, has been investigated at T = 40 °C within a range of supersaturations (σ = 0.040 and 0.080), in the presence of varying raffinose concentrations (0.0 ≤ Craff ≤ 8.0% H2O). Raffinose dramatically slows down the growth rate of the first three forms, modifies the shape of their growth isotherms and can induce dead zones as well, the effects increasing with its concentration. However, the screw dislocation mechanism maintains. The comparison between Kubota‐Mullin and Cabrera‐Vermilyea kinetic models shows that the first one better describes our experimental data. This allows to deduce that the raffinose adsorption mainly occurs at the kinks sites of all the interested forms. Moreover, the values of the effectiveness coefficient of KM model shows the combined effects of supersaturation and raffinose concentration in the growth solutions. On the contrary, the {$ \bar 1 $$ \bar 1 $0} form is weakly affected by raffinose, owing to the low structural compatibility between its kinks and the additive molecules. Finally, the changes of the crystal morphology, induced by the highly anisotropic kinetic effects, were studied as well. Increasing raffinose concentration and supersaturation produces conflicting effects on the morphology: the first one promotes crystals elongated in the [010] direction and reduces the number of forms on the crystals, while supersaturation acts in the opposite sense. Ratios among the main dimensions of crystals are critically discussed to evaluate their final shapes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Different contributions of insulin resistance and beta‐cell dysfunction in overweight Israeli Arabs with IFG and IGT
Authors: Abdul‐Ghani Muhammad A. , Sabbah Muhammad , Kher Joseph , Minuchin Oscar , Vardi Pnina , Raz Itamar 
Published: September 2005

AbstractBackgroundImpaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are both intermediate stages that exist between normal glucose tolerance and overt type 2 diabetes. Epidemiological studies demonstrated that the two categories define distinct populations. In this study, we examined the contributions of insulin resistance and beta‐cell dysfunction to both states in overweight subjects of Arab origin.MethodsTwelve subjects with isolated IFG, 10 with isolated IGT, and 20 with IFG and IGT (combined glucose in tolerance—CGT) were compared with 30 subjects with normal glucose tolerance (NGT) subjects; all were of Arab origin and were overweight or obese. Different indices for insulin resistance and beta‐cell function were calculated from oral glucose tolerance (OGTT) values.ResultsSubjects with isolated IFG and CGT were more obese and had significantly higher values of insulin resistance than subjects with isolated IGT and NFG. There was no significant difference between the insulin resistance in subjects with isolated IGT and that in subjects with NGT. Indices of beta cell function were severely reduced among subjects with isolated IGT and CGT when compared with those with both isolated IFG and NGT, while subjects with isolated IFG had similar beta‐cell indices to subjects with NGT.ConclusionThese data demonstrate that beta‐cell dysfunction and insulin resistance contribute differently to the pathogenesis of IFG and IGT among overweight Arab subjects. Copyright © 2005 John Wiley & Sons, Ltd.
Regional sustainable development in France: assessing the environmental implications
Authors: Bertrand F. , Larrue C. 
Published: September 2005

AbstractThis article considers the environmental dimension of regional sustainable development in France. The first part evaluates the position of the environment in regional sustainable development policies using two levels of analysis. First, it examines the stated objectives for regional sustainable development that relate to a balanced integration of the environmental dimension in relation to the economic and social dimensions. Second, it demonstrates how efforts to implement regional sustainable development (RSD) invariably lead to domination by environmental factors, as a consequence of well established environmental policies. Thereafter, a critical analysis of this outcome is presented, illustrating how the disparity between what is said and done has produced an ambiguous notion of sustainable development (SD), and how different actors have adopted strongly opposing views. This confusion has created resistance by environmental actors, who perceive sustainable development as potentially diluting environmental demands. The article concludes by discussing the possible future role of the environment within regional sustainable development. Copyright © 2005 John Wiley & Sons, Ltd and ERP Environment.