bluuebunny/crossref_metadata_2025_split huggingface dataset:
Al/Ni : V/Ag metal stacks as rear‐side metallization for crystalline silicon solar cells
Authors: Jung Verena , Köntges Marc 
Published: February 2012

ABSTRACTRear sides of crystalline silicon solar cells are usually covered with aluminum on which it is difficult to solder. To ease soldering, we present a durability study for a Ni : V/Ag stack on evaporated Al as rear‐side metallization. We adapt this cost‐effective metallization stack from the microelectronic industry and investigate it as metallization for silicon solar cells. Here, a long‐term stability of the metallization and of the solder joint must be guaranteed for 25 years and is therefore evaluated in detail by thermal aging experiments. During this experiment, the mechanical stability of the solder joints is measured. The chemical stability and the intermetallic compound (IMC) growth within the solder joints are examined by secondary electron microscopy, backscattered electron imaging, and energy dispersive X‐ray analysis. Experiments with either a Sn–Ag‐coated copper tab or pure Sn–Ag solder show two different sorts of IMCs at the Ni : V/Solder interface. With the copper tab, a Cu–Ni–Sn compound, presumably (Cu1 ‐ xNix)6Sn5, grows at the Ni/solder interface, whereas in case of a pure Sn–Ag solder, a Ni–Sn compound grows, which is likely to be Ni3Sn4. Analysis of the reaction kinetics leads to activation energies of 77 and 42 kJ/mol, respectively, for a diffusion‐controlled IMC growth. By using temperature histograms of PV modules in the field, the necessary minimum Ni : V layer thickness is estimated: without a copper tab up to 1.6 µm Ni and with a copper tab less than 0.2 µm may be consumed by IMC formation during 25 years of lifetime. Copyright © 2012 John Wiley & Sons, Ltd.
Inclinable Shear Box Simulations of Deepening Active Layers on Perennially Frozen Scree Slopes
Authors: Rist A. , Phillips M. , Springman S. M. 
Published: February 2012

ABSTRACTA series of systematic shear tests were performed using an inclinable shear box containing a coarse‐grained active layer overlying a fine‐grained permafrost layer, a stratigraphy observed in the field. The angle of mobilised interface friction Φmob was determined as depending on the grain size of the active layer and the permafrost, the water content of the active layer and the ice content of the permafrost. Φmob was found to be 8° lower for ice‐free permafrost compared to permafrost containing ice. This result implies a possible long‐term decrease of active‐layer slope stability on scree slopes in Alpine permafrost terrain under warming conditions. Copyright © 2012 John Wiley & Sons, Ltd.
Influence of permafrost on water storage in West Siberian peatlands revealed from a new database of soil properties
Authors: Smith Laurence C. , Beilman David. W. , Kremenetski Konstantin V. , Sheng Yongwei , MacDonald Glen M. , Lammers Richard B. , Shiklomanov Alexander I. , Lapshina Elena D. 
Published: February 2012

ABSTRACTRussia's West Siberian Lowland (WSL) contains the most extensive peatlands on Earth with many underlain by permafrost. We present a new database of 12 705 measurements of vertical water content and bulk soil properties from 98 permafrost and non‐permafrost cores collected in raised bogs and peat plateaus across the region, together with in‐situ measurements of surface moisture and thaw depth, botanical descriptions of dominant surface vegetation species assemblage, and field notes. Data analyses reveal significant contrasts (p < 0.01 to p < 0.0001) between permafrost and non‐permafrost sites. On average, permafrost WSL peatlands exhibit drier surfaces, shallower depth, lower organic matter content and higher bulk density than do non‐permafrost sites. Peat bulk density and ash‐free density increase with depth for non‐permafrost but not for permafrost sites. Gravimetric water content averages 92.0% near the surface and 89.3% at depth in non‐permafrost, but 81.6% and 85.4%, respectively, in permafrost, suggesting that the disappearance of permafrost could produce moister surfaces across the WSL. GIS extrapolation of these results suggests that WSL peatlands may contain ~1200 km3 of water and ice, a large storage equivalent to ~2‐m average liquid water depth and approximately three times the total annual flow in the Ob' River. A global estimate of ~6900‐km3 subsurface water storage for all northern peatlands suggests a volume comparable to or greater than the total water storage in northern lakes. The database is freely available as supplementary material for scientific use at http://onlinelibrary.wiley.com/doi/10.1002/ppp.735/suppinfo. Copyright © 2012 John Wiley & Sons, Ltd.
Characterization and Analysis of Tetranitrate Esters
Authors: Oxley Jimmie C. , Smith James L. , Brady Joseph E. , Brown Austin C. 
Published: February 2012

AbstractThermal behaviors, vapor pressures, densities, and drop weight impact results, as well as analytical protocols, are reported for three tetranitrate esters: erythritol tetranitrate (ETN), 1,4‐dinitrato‐2,3‐dinitro‐2,3bis(nitratomethylene) butane (DNTN), and pentaerythritol tetranitrate (PETN). ETN and DNTN both melt below 100 °C and have ambient vapor pressures comparable to TNT. While LC/MS was shown to be a viable technique for analysis of all three tetranitrate esters, only ETN was successfully analyzed by GC/MS. Performance of these nitrate esters as evaluated in lab using the small‐scale explosivity device (SSED) suggested RDX≫DNTN>PETN>ETN. Detonation velocities were calculated using Cheetah 6.0. Since the starting material is now widely available, it is likely that law enforcement will find ETN in future improvised explosive devices. This paper with its analytical schemes should prove useful in identification of this homemade explosive.
The complex symbiotic relationships of bark beetles with microorganisms: a potential practical approach for biological control in forestry
Authors: Popa Valentin , Déziel Eric , Lavallée Robert , Bauce Eric , Guertin Claude 
Published: February 2012

AbstractBark beetles, especiallyDendroctonusspecies, are considered to be serious pests of the coniferous forests in North America. Bark beetle forest pests undergo population eruptions, causing regionwide economic losses. In order to save forests, finding new and innovative environmentally friendly approaches in wood‐boring insect pest management is more important than ever. Several biological control methods have been attempted over time to limit the damage and spreading of bark beetle epidemics. The use of entomopathogenic microorganisms against bark beetle populations is an attractive alternative tool for many biological control programmes in forestry. However, the effectiveness of these biological control agents is strongly affected by environmental factors, as well as by the susceptibility of the insect host. Bark beetle susceptibility to entomopathogens varies greatly between species. According to recent literature, bark beetles are engaged in symbiotic relationships with fungi and bacteria. These types of relationship are very complex and apparently involved in bark beetle defensive mechanisms against pathogens. The latest scientific discoveries in multipartite symbiosis have unravelled unexpected opportunities in bark beetle pest management, which are discussed in this article. Copyright © 2012 Society of Chemical Industry
Electrical characterisation of GaN and AlGaN layers grown by plasma‐assisted MBE
Authors: Kolkovsky V. , Scheffler L. , Sobanska M. , Klosek K. , Zytkiewicz Z. R. , Weber J. 
Published: February 2012

AbstractIn the present study GaN and Alx Ga1‐x N layers (with x below 5%) grown by plasma‐assisted MBE (PAMBE) were investigated by deep level transient spectroscopy (DLTS) and high‐resolution Laplace DLTS. In GaN a dominant DLTS peak was observed at about 120 K. Using the high‐resolution Laplace DLTS technique we demonstrate that this peak consists of two close components. Defects related to the nitrogen vacancy are the most probable candidates for the origin of these levels. Two other dominant peaks were observed in the DLTS spectra in AlxGa1‐xN layers with x = 1.4% and x = 3%, respectively. The position of the peaks depends on the Al content and shifts towards higher temperatures with Al concentration. The electrical properties of the peaks and their origin will be discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zn doped GaN for single‐photon emission
Authors: Behrends Arne , Ledig Johannes , Al‐Suleiman Mohamed Aid Mansur , Peters Silke , Racu Ana Maria , Schmunk Waldemar , Hofer Helmut , Kück Stefan , Bakin Andrey , Waag Andreas 
Published: February 2012

AbstractIn this work we report on the optical investigation of Zn doped GaN films fabricated by metal organic chemical vapor deposition. The samples show bright emission in the blue spectral range around 2.9 eV when Si codoping is provided. This emission is suggested to be used for single‐photon emission, thus the density of the Zn‐Si pairs was drastically reduced leading to a decrease of the blue luminescence. For electrically excited single‐photon sources these Zn‐Si pairs have to be incorporated into LEDs, therefore we fabricated GaN‐based nano‐LEDs which show electroluminescence at 430 nm (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of ZnO:Al‐based transparent contacts deposited at low‐temperature by RF‐sputtering on InN layers
Authors: Fernández S. , Naranjo F. B. , de Abril O. , Valdueza‐Felip S. 
Published: February 2012

AbstractNitride semiconductors (Al,Ga,In)N attain material properties that make them suitable for photovoltaic and optoelectronics devices to be used in hard environments. These properties include an energy gap continuously tuneable within the energy range of the solar spectrum, a high radiation resistance and thermal stability. The developing of efficient devices requires contacts with low resistivity and high transmittance in visible region. ZnO:Al (AZO) emerges as a feasible candidate for transparent contact to nitride semiconductors, taking advantage of its low resistivity, high transparency in visible wavelengths and a very low lattice mismatch with respect to nitride semiconductors. This work presents a study of the applications of AZO films deposited at low‐temperature by RF magnetron sputtering as transparent contact for InN layers. The optimization of AZO conditions deposition lead to the obtaining of contacts which shows an ohmic behaviour for the as‐deposited layer, regardless the thickness of the ZnO:Al contact layer. Specific contact resistances of 1.6 Ω·cm2 were achieved for the contact with 90 nm thick ZnO:Al layer without any post‐deposition treatment (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electromodulation spectroscopy of optical transitions and electric field distribution in GaN/AlGaN/GaN transistor heterostructures with various AlGaN layer thicknesses
Authors: Kudrawiec R. , Gladysiewicz M. , Misiewicz J. , Siekacz M. , Cywinski G. , Wolny P. , Skierbiszewski C. 
Published: February 2012

AbstractGaN/AlGaN/GaN field effect transistor (FET) heterostructures with various thicknesses of AlGaN layer (10, 20, and 30nm) were investigated by electromodulation spectroscopy [i.e. contactless electroreflectance (CER) and photoreflectance (PR)]. In PR spectra optical transitions in GaN cap, AlGaN and GaN buffer layers were clearly observed whereas in CER spectra the optical transition in GaN buffer layer was not observed due to the screening of band bending modulation in CER spectroscopy by the two dimensional electron gas at the AlGaN/GaN interface. The transition related to GaN‐cap was observed ∼0.1 eV above the energy gap of GaN due to the quantum confinement in the surface GaN quantum well. The built‐in electric field in AlGaN layer was determined from the analysis of AlGaN‐related Franz‐Keldysh oscillation. For the sample with 10, 20, and 30nm thick AlGaN layer the electric field has been determined from CER(PR) measurements to be 0.30(0.27), 0.46(0.39) and 0.78(0.63) MV/cm, respectively. The smaller electric field, which is obtained from PR measurements, results from the photovoltaic effect which is eliminated in CER spectroscopy. The electric field distribution in the full heterostructure (GaN(cap) layer, AlGaN layer, and near the AlGaN/GaN interface in GaN(buffer) layer) has been found comparing theoretical calculations for the full heterostructure with the electric field for AlGaN layer obtained from CER measurements. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of the transition from weak to strong exciton‐photon coupling regime in a GaAs microcavity: angle resolved measurements
Authors: Belykh V. V. , Mylnikov D. A. , Sibeldin N. N. 
Published: February 2012

AbstractThe emission dynamics of a GaAs microcavity with embedded quantum wells at different angles of observation with respect to the sample normal under conditions of nonresonant picosecond‐pulse excitation is studied. At considerably high excitation densities, above a certain threshold, a very intense, fast, and spectrally narrow (at small angles of observation) component in the PL dynamics appears at short times, with the spectral position corresponding to the bare cavity mode, indicating the onset of lasing in the weak coupling regime. At longer times lasing ceases and the transition from weak to strong coupling regime is observed, as it follows from the spectral positions of the peaks in time‐resolved spectra at different angles of observation.At moderate excitation densities, kinetic dependences of the spectral shift and width of the lower polariton emission line (these parameters are often used to distinguish between strong and weak coupling regimes) as a function of angle of observation (polariton energy) are analyzed. In particular, it is shown that the decay time of the spectral shift is almost independent of the polariton energy and could be used as the characteristic time of the transition from weak to strong coupling regime. On the other hand, the decay time of the emission line broadening strongly depends on the polariton energy, indicating that the linewidth kinetics is essentially determined by the cooling of the electron‐hole system. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and characterization of CdxMn1‐xS magnetic nanoparticles stabilized with poly(vinyl alcohol) for biomedical applications
Authors: Schatkoski Vanessa , Mansur Alexandra , González Juan , Mansur Herman 
Published: February 2012

AbstractIn this work we report the synthesis and characterization of CdxMn1‐xS nanoparticles using poly(vinyl alcohol) as stabilizing agent aiming at the production of quantum dots nanocrystals with photoluminescence properties. UV‐visible spectroscopy (UV‐vis), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM) were used to characterize the formation and the relative stability of CdS nanoparticles. The results have clearly shown the influence of the Mn2+ partially replacing Cd2+ in the optical behavior of the semiconductor QDs produced. Moreover, the TEM images have not indicated any detectable segregation or phase separation caused by the amount of Mn+2 added to the CdS system (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon diffusion and reactivity in Mn5Ge3 thin films
Authors: Petit Matthieu , Dau Minh Tuan , Monier Guillaume , Michez Lisa , Barre Xavier , Spiesser Aurelie , Thanh Vinh Le , Glachant Alain , Coudreau Cyril , Bideux Luc , Robert‐Goumet Christine 
Published: February 2012

AbstractThe Curie temperature of Mn5Ge3 has been successfully enhanced by carbon doping. In this context the diffusion of a carbon thin film in Mn5Ge3 has been studied at room temperature. A value of the diffusivity of about D = 2.4 × 10‐23 ± 0.5 × 10‐23 m2 s‐1 is reported. This value is in the typical range of interstitial diffusion coefficients. Moreover Auger Ge and Mn peaks shifts and Ge3d core level have been investigated to get some details on the reactivity of carbon atoms in Mn5Ge3.Mn Auger transitions display a shift of 4 eV whereas Ge transitions do not. Similarly Ge3d core level does not contain C related contribution but presents a Mn one. These observations confirmed the fact that carbon atoms are not inert species for Mn. It suggests that a ternary Ge‐Mn‐C alloy could occur and should be taken into account when doping the Mn5Ge3 with carbon. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adsorption of OH and H at the LiNbO3(0001) surface
Authors: Hölscher R. , Sanna S. , Schmidt W. G. 
Published: February 2012

AbstractThe adsorption of single hydrogen atoms and hydroxyl radicals (OH) at the polar (0001) surface is simulated by means of first‐principles total energy calculations, in order to investigate the influence of ferroelectric poling on the surface physics and chemistry of LiNbO3. H and OH are found to adsorb at a similar site both at the positive and at the negative (0001) surface. Despite this, the adsorption energy is for both adsorbates strongly polarization dependent, with adsorption energy differences as high as 2 eV. This striking contrast is traced back to electrostatic effects, which lead to a different bonding scenario at the two LN(0001) sides. The polar radical OH lies relatively flat on the positive surface, with the adsorbate oxygen forming a covalent bond with the surface oxygen. At the negative face, OH adsorbs roughly perpendicular and the adsorbate oxygen forms a bond of covalent nature with the surface cations. The adsorbate dipole moment is directed against the spontaneous polarization of the substrate. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of ultra‐thin nitridation layer on Si(100) by hot‐wire method
Authors: Inao Haruki , Izumi Akira 
Published: February 2012

AbstractIn this work we study the deposition of indium oxynitride prepared by reactive RF magnetron sputtering. This material shows multi‐functionality in electrical and photonic applications. It shows transparence in visible range, wide band gap, high resistivity, low linkage current and response for light. The deposition processes were performed in a home build magnetron sputtering system, using a four‐inch pure In (99.999%) target, nitrogen and oxygen as process gases. The pressure was kept constant in 1.33 Pa and the RF power (13.56 MHz) was constant 250 W. The optical band gap was estimated for samples deposited with 0%, 10%, 20%, 50%, 80% and 85% of oxygen concentration in the gas mixture and the band gap values obtained were 1.32 eV, 2.47 eV, 2.65 eV, 2.50 eV, 3.04 eV and 3.00 eV, respectively. The IxV analysis shows a low leakage current (∼10–8 A). The increase in the oxygen concentration in the plasma promotes change in the character of these thin films from conductor to semiconductor material (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adsorption of 5,10,15,20‐tetrakis (4‐bromophenyl)porphyrin on germanium(001)
Authors: Berner N. C. , Sergeeva Y. N. , Sergeeva N. N. , Senge M. O. , Cafolla A. A. , McGovern I. T. 
Published: February 2012

AbstractA comparative study of 5,10,15,20‐tetrakis(4‐bromophenyl)porphyrin and 5,10,15,20‐tetraphenylporphyrin molecules adsorbed on the Ge(001) surface, using scanning tunnelling microscopy and photoemission spectroscopy, reveals that the bromine substituents influence the adsorption mechanism significantly. A strong bromine‐germanium interaction is observed, affecting the adsorption geometry of the entire molecule. Neither molecule appears to be mobile on the surface, which indicates additional interaction between the macromolecule and the surface. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interface state characterization of ALD‐Al2O3/GaN and ALD‐Al2O3/AlGaN/GaN structures
Authors: Hori Yujin , Mizue Chihoko , Hashizume Tamotsu 
Published: February 2012

AbstractWe have characterized the interface states of Al2O3/GaN and Al2O3/AlGaN/GaN structures prepared by atomic layer deposition using the conventional and photo‐assisted capacitance‐voltage (C–V) measurements. In order to control the interface states, an N2O‐radical treatment was applied to the GaN and AlGaN surfaces prior to the deposition of the Al2O3 layer. We observed good C–V behavior and a relatively low density of interface states for the N2O‐radical treated Al2O3/GaN structure. To estimate the state density distributions at the Al2O3/AlGaN interface, we applied the photo‐assisted C–V measurement to the Al2O3/AlGaN/GaN heterostructures. The present Al2O3/AlGaN structre showed higher interface state densities than the Al2O3/GaN structure. However, we found that the N2O‐radical treatment is effective in reducing the density of interface states at the Al2O3/GaN and Al2O3/AlGaN systems (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of boron‐nitride ultra‐thin films on Si(111)
Authors: Shimoyama Iwao , Baba Yuji , Sekiguchi Tetsuhiro , Nath Krishna G. 
Published: February 2012

AbstractChemical vapor deposition is employed to form hexagonal boron nitride (h ‐BN) monolayer films on Si(111) with a borazine precursor. The electronic structure and orientation of the films are analyzed by near edge X‐ray absorption fine structure (NEXAFS) spectroscopy and X‐ray photoelectron spectroscopy (XPS). XPS analysis shows that monolayer‐level stoichiometric BN films were formed. The B K‐edge NEXAFS spectra show two discrete peaks that have graphite‐like polarization dependence in the low‐energy region. Polarization dependence analysis of the NEXAFS indicates that the BN films had two‐dimensional orientation on the Si(111) substrate. Based on the density functional theory calculations, these discrete peaks are assigned to π* peaks at an intact h ‐BN site and edge B‐H site. Comparison with the electronic structures of bulk h ‐BN and h ‐BN/Ni(111) clarifies that the interaction between the BN layer and Si substrate was very small. This indicates that the h ‐BN monolayer was physisorbed on Si(111), making a steep interface and conserving the intrinsic electronic structure (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Heterojunction characteristics of ZnO and CuO substrates formed by direct bonding
Authors: Abe Hiroshi , Fujishima Masahide , Komiyama Takao , Chonan Yasunori , Yamaguchi Hiroyuki , Aoyama Takashi 
Published: February 2012

AbstractThe n‐ZnO/p‐CuO heterojunction characteristics have been investigated by direct bonding of ZnO and CuO substrates at room temperatures, and by post‐annealing at 800ºC. The ZnO substrate was fabricated by mixing of ZnO and Al2O3 (2%) powders, pressing at 50 MPa, and sintering at 1400 °C while the CuO substrate was fabricated by mixing of CuO and Li2CO3 (1%) powders, pressing at 300 MPa, and sintering at 700 °C. Rectifying behaviour with an ideality factor of 126 was observed after bonding of these substrates. Post‐annealing of the heterojunction, however, significantly increased both the forward and the reverse currents, and the rectifying behaviour was lost. Symmetrical I‐V curves with threshold voltages of about ± 1 V were observed and this degradation could be explained by impurity (Al and Li) segregation at the junction interface. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The structural and material properties of Cu(In,Ga)Se2 thin films
Authors: Wu Ya‐Fen , Hsu Hung‐Pin , Wang Jen‐Cheng , Chen Hui‐Ying 
Published: February 2012

AbstractWe report on the structural and material properties of Cu‐poor CuIn1‐xGax Se2 (CIGS) thin films with different gallium contents grown using the co‐evaporation technique. Temperature‐dependent photoluminescence (PL) and high‐resolution X‐ray diffraction measurements were performed. The PL emission peaks observed around 1.0‐1.2 eV are attributed to donor‐acceptor pair luminescence. These donor‐acceptor pair emissions are considered to originate from relatively shallow acceptor and donor energy levels. In addition, the X‐ray diffraction spectra of the samples are simulated using a theoretical model. From the analysis, it is found that the sample with higher gallium content exhibits smaller grain size and the microstructure size uniformity is reduced. The theoretical calculation result is consistent with the experimental results derived from the PL spectra. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)