bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of etching on Ge(111) surfaces and Pd Schottky contacts
Authors: Nel J. M. , Griffiths T. C. , van Schalkwyk L. , Auret F. D. , Hayes M. , van den Berg N. 
Published: January 2008

AbstractThe etch rates of various etches and the resulting morphology of the Ge (111) surface have been investigated using atomic force microscopy (AFM) techniques and the oxidation rate of the germanium after etching was monitored by ellipsometry. The effect of the etch on the stability of Pd Schottky barrier diodes (SBDs) was monitored over a period of time using current voltage measurements. It was found that those etches with high etch rates produced much rougher surfaces which in turn showed significant variation in the leakage currents of SBDs deposited on these surfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Piezospectroscopic analysis of mobile defects in semiconducting materials
Authors: Dobaczewski L. , Peaker A. R. , Markevich V. P. , Hawkins I. D. , Nielsen K. Bonde 
Published: January 2008

AbstractThe piezospectroscopic analysis of point defects allows to describe fixed defects embedded in a crystal environment of immobile atoms. This description works well when all atoms vibrate around fixed equilibrium positions and these vibrations are much faster than the time scale of the experiment while the equilibrium positions do not evolve within this time scale. For some defects this condition is not fulfilled at temperatures of the DLTS experiment, which somehow is reflected in a departure from what the theory predicts. On the other hand, systematic discrepancies between results of theoretical piezospectroscopic analysis and experiment can be a valuable source of information about a defect. We discuss how these re‐orientation processes can be identified from the observed piezospectroscopic parameters for a number of defect complexes observed in silicon and germanium with the use of the high‐resolution Laplace Deep Level Transient Spectroscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of band anticrossing in InGaPN alloys grown on GaAs substrates
Authors: Lin K. I. , Lin H. C. , Wang T. S. , Lee M. H. , Hwang J. S. 
Published: January 2008

AbstractThe band anticrossing (BAC) model is introduced to describe the influence of the incorporated nitrogen on the band structure of dilute nitrides. An isolated N introduces highly localized states in these nitrides, which interact with the extended conduction‐band states of the host semiconductor. The interaction splits the conduction band into an upper and a lower subband. There are reports of the band‐gap reduction in InGaPN, but no experimental observations of the upper subband have been reported. In this work, temperature‐dependent photoreflectance (PR) and photoluminescence (PL) spectra are employed to examine the band structure of InGaPN/GaAs heterostructures. Besides the band gap, the upper subband predicted by the BAC model is observed in the PR spectra. By eliminating the contributions of the strain and ordering effects in InGaPN, and assigning the localized state energy EN introduced by an isolated N to be 2.04 eV at 293 K, the interaction potential is determined as 1.449±0.170 eV. With N incorporation, the PL peak energy exhibits a particular behavior with temperature, which is not observed in the PR spectra. This is attributed to carrier localization at low temperatures occurring in N‐diluted semiconductors. Additionally, the temperature dependence of the band gap is described by the BAC model incorporating two different EN levels, either constant or temperature‐dependent. In our hands, the assumption of the temperature‐dependent EN level results in a better fit with the experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An investigation of thermal boundary resistance in 1.3 µm edge‐emitting dilute nitride quantum well laser diodes
Authors: MacKenzie R. , Lim J. J. , Bull S. , Sujecki S. , Larkins E. C. 
Published: January 2008

AbstractA theoretical investigation into the impact of the thermal boundary resistance on the performance of uncooled edge‐emitting 1.3μm InGaAsN/GaAs quantum well lasers has been performed. A state‐of‐the‐art 2D laser diode simulation tool has been extended to accurately model the thermal resistance due to the acoustic material mismatch and defect scattering at epitaxial interfaces. A small, but noticeable, increase in quantum well temperature is observed. The results clearly highlight the need for the inclusion of thermal boundary resistance in device simulation tools. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermally dependent gain of 1.3 µm dilute nitride double quantum well lasers
Authors: MacKenzie R. , Bull S. , Lim J. J. , Chao S. , Sujecki S. , Sadeghi M. , Wang S. M. , Larsson A. , Melanen P. , Sipilä P. , Uusimaa P. , Larkins E. C. 
Published: January 2008

AbstractA systematic study of the dependence of the optical gain on the injection current and temperature in InGaAsN/GaAs lasers has been performed. The amplified spontaneous emission has been measured from a series of both facet‐coated and uncoated 1.3 μm edge‐emitting double quantum well lasers. The net gain, modal gain, cavity loss, quasi‐Fermi level separation and width of the gain spectra have been extracted using Cassidy's method. The peak gain was found to shift 0.41 nm/K between 300 K and 340 K and 0.60 nm/K between 340 K and 380 K. The value of the peak gain was found to decrease with temperature at a rate of 0.26 cm−1/K. The increase in the full at width half maxima of the gain spectra was determined to be 0.35 nm/K. These values are all comparable to those found for the more traditional 1.3 μm InP‐based devices, suggesting that InGaAsN/GaAs lasers are a viable alternative to replace such InP‐based devices, in particular for uncooled access network applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence microscopy investigation of lattice relaxation and defect formation processes in pseudomorphically strained InGaAsN multiple quantum wells
Authors: Lu W. , Chao S. , Bull S. , Andrianov A. V. , Grant V. A. , Campion R. P. , Foxon C. T. , Sadeghi M. , Wang S. M. , Larsson A. , Larkins E. C. 
Published: January 2008

AbstractPhotoluminescence microscopy (PLM) and photoluminescence (PL) spectroscopy have been used to investigate the influences of the number of quantum wells (QWs) and nitrogen concentration [N] on the quality of InGaAsN multiple QWs (MQWs). No misfit dislocations and/or carrier localization were observed in as‐grown InGaAsN MQWs. PL measurement results suggest that the PL efficiency and interfaces in the InGaAsN/GaAs QWs do not deteriorate with increasing number of QWs. In an InGaAsN 7 QW structure, even after annealing at temperatures as high as 850 °C, misfit dislocations were still not observed. This is contrary to the lattice relaxation behaviour of annealed InGaAs MQWs and is attributed to the impurity pinning of dislocations by nitrogen. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Fermi level position in as‐grown GaInNAs(Sb) quantum wells and layers studied by contactless electroreflectance
Authors: Kudrawiec R. , Yuen H. B. , Bank S. R. , Bae H. P. , Wistey M. A. , Harris J. S. , Motyka M. , Gladysiewicz M. , Misiewicz J. 
Published: January 2008

AbstractIt is shown that the Fermi level in as‐grown GaInNAs(Sb) material wants to be pinned at an energy which is located very close to the Fermi level‐stabilization energy (EFS). For 7.5‐nm‐thick GaInNAs(Sb) layers (quantum wells in fact) this energy lies ∼0.9 eV above the GaAs valence band whereas the EFS is known to be located ∼4.9±0.2 eV below the vacuum level (∼0.6 eV above the GaAs valence band). Increased the GaInNAs(Sb) layer thickness to 100 nm the Fermi level pinning shifts closer to the Fermi level‐stabilization energy and is located ∼0.8 eV above the GaAs valence band. This observation is associated with this fact that the ability to pin the Fermi level close to the EFS enhances when the total number of N‐related native point defects increased. In this case, the total number of point defects increases because of the increase in GaInNAs(Sb) thickness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mg doping of InN and the use of yttrium‐stabilised zirconia substrates
Authors: Swartz C. H. , Durbin S. M. , Anderson P. A. , Carder D. , Reeves R. J. , Chandril S. , Myers T. H. , Kennedy V. J. , Ahrenkiel S. P. 
Published: January 2008

AbstractDetermining fundamental properties of InN is beset with difficulties. Since a conducting surface accumulation layer creates difficulties when assessing the impact of dopants, variable magnetic field Hall effect measurements were performed to separate various conducting layers. In addition to verifying p‐type doping with Mg, variable magnetic field Hall effect was used to show that growth of InN on YSZ will greatly reduce the background n‐type concentration for thinner layers, (with n ∼ 2×1017 cm−3, the lowest achieved on half micron thick material), making microns‐thick growth less important than the typical method of growth on sapphire with GaN buffer layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier‐induced refractive index change in InN
Authors: Bulutay C. , Zakhleniuk N. A. 
Published: January 2008

AbstractRapid development of InN technology demands comprehensive assessment of the electronic and optoelectronic potential of this material. In this theoretical work the effect of free electrons on the optical properties of the wurtzite phase of InN is investigated. The blue shift of the optical absorption edge by the free‐carrier band filling is known as the Burstein‐Moss effect for which InN offers to be a very suitable candidate as has been recently demonstrated experimentally. Due to well known Kramers‐Kronig relations, a change in absorption is accompanied by a change in the index of refraction. Considering n‐type InN samples with free electron concentrations ranging from 5×1017 to 5×1020 cm−3, and employing a nonlocal empirical pseudopotential band structure, it is shown that this leads to a few percent change of the index of refraction. These carrier‐induced refractive index changes can be utilized in optical switches, futhermore it needs to be taken into account in the design of InN‐based optical devices such as lasers and optical modulators. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure of cubic polytype indium nitride layers on top of modified sapphire substrates
Authors: Morales F. M. , Lozano J. G. , García R. , Lebedev V. , Wang Ch. Y. , Cimalla V. , Ambacher O. , González D. 
Published: January 2008

AbstractThe occurrence of cubic indium nitride thin layers grown by molecular beam epitaxy on top of c‐plane sapphire substrates modified by an intermediate layer of cubic indium oxide is reported. An orientation relationship between the (0001) plane of Al2O3and both (001) surfaces of body‐centered cubic In2O3and zinc‐blende InN is demonstrated by means of electron and X‐ray diffraction and by transmission electron microscopy. We propose that the demonstrated approach is able to stabilize the non equilibrium phase of InN (i. e., the cubic polytype) due to a low lattice mismatch together with a four fold surface atomic arrangement of the indium oxide‐indium nitride interface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of SiNx:Hy passivant layers for AlGaN/GaN high electron mobility transistors
Authors: Redondo‐Cubero A. , Gago R. , Romero M. F. , Jiménez A. , González‐Posada F. , Braña A. F. , Muñoz E. 
Published: January 2008

AbstractIn this work, hydrogenated silicon nitride (SiNx:Hy) grown by chemical vapour deposition as passivant layers for high electron mobility transistors (HEMT) have been studied. The film composition and bonding structure were determined by ion beam analysis and x‐ray absorption spectroscopy techniques, respectively. The effects of gas precursors (SiH4/N2 and SiH4/NH3) and film/substrate interface on the film growth have been addressed. The growth on different substrates (Si, GaN, AlGaN), and the effects of plasma pre‐treatments have been studied before the growth and the film growth evolution. Results yield no significant differences in all the analysed samples. This points out the relevant role of SiHn radicals as growth precursor species and that intrinsic characteristics of the SiNx:Hy layers are not affected by the film/substrate interface. Hence, improved performance of HEMT with surface plasma pre‐treatments before passivation should be related to extrinsic mechanisms (such as creation of defects in AlGaN surface, removal of the surface contamination or ion‐induced roughness). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High temperature instabilities of ohmic contacts on p‐GaN
Authors: Trevisanello Lorenzo , Meneghini Matteo , Zehnder Ulrich , Hahn Berthold , Meneghesso Gaudenzio , Zanoni Enrico 
Published: January 2008

AbstractThis paper describes an investigation of the instabilities of ohmic contacts on p‐type GaN submitted to long term high temperature stress. Transfer Length Method (TLM) was used to separately analyze the contribution of contact resistivity and sheet resistance on contact degradation. Before treatment, contacts showed linear behaviour, indicating good ohmic properties. On the other hand, thermal ageing at 250 °C induced the degradation of electrical characteristics: in particular, (i) an increase of the contact resistivity was detected after stress, as well as (ii) a rectifying behaviour in current‐voltage (IV) characteristics of contact appeared. The degradation process has been ascribed to the diffusion of an atomics species from PECVD‐deposited passivation layer to p‐type ohmic contact: the interaction of this species with acceptor dopant can lower acceptor concentration, thus broadening the Schottky barrier at the interface and inducing the observed non‐linearity of the contacts. The square root time dependence of degradation of the electrical characteristics agreed with the hypothesis of diffusion. After 160 hours of aging, the passivation layer was removed and the structures were submitted to a new thermal treatment. This further treatment was found to induce the recovery of the electrical characteristics of the contacts, due to the fact that passivation acts like (i) a source of atomic species responsible of diffusion and/or (ii) a blocking layer for these species: the removal of passivation stopped the diffusion process and make outgassing process possible. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructured horizontal alumina pore arrays as growth templates for large area few and single nanowire devices
Authors: Xiang Ying , Lee Woo , Nielsch Kornelius , Abstreiter Gerhard , Fontcuberta i Morral Anna 
Published: January 2008

AbstractWe demonstrate the fabrication of horizontally aligned and well‐defined nanopore structures by anodic oxidation of aluminum thin films and micro stripes on a Si substrate. We are able to control both, the pore diameters and interpore distances from 10 nm to 130 nm and from 30 nm to 275 nm, respectively. The anisotropy of the system induces some deviations in the pore configuration from the typical honeycomb structure. By decreasing the dimensions of the Al structures, the final pore diameter and interpore distance remains constant, enabling the transition from multiple to a few nanowire porous structures. Finally, we successfully filled the nanopores by pulsed electroplating, as demonstrated both by Scanning Electron Microscopy and by current–voltage measurements. Having full control over the size, the density, the position and the orientation of the porous structure, our approach is promising for many exciting applications, including nanoelectronics and sensing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface chemical and nanomechanical alterations in plasma immersion ion implanted PET
Authors: Kereszturi Klára , Tóth András , Mohai Miklós , Bertóti Imre 
Published: January 2008

AbstractPoly(ethylene terephthalate) (PET) surface was treated by plasma immersion ion implantation (PIII or PI3) in nitrogen. The treatment conditions like acceleration voltage, ion fluence and fluence rate were varied systematically. The PIII‐induced alterations in the surface chemical composition and bonding of the constituent elements were studied by XPS. Nanoindentation and nanoscratch measurements were applied to investigate the related changes in the hardness, elastic modulus and wear resistance. Nitrogen PIII treatment of PET led to incorporation of nitrogen and decrease of surface O/C ratio. The bulk plasmon loss energy of the C 1s peak increased, implying compaction of the surface layer. PIII treatment increased the mean surface roughness and hardness (H), and decreased the elastic modulus (E). Process conditions were found, under which a four‐fold increase was obtained in the wear resistance. Improvement in wear resistance was accompanied by increase in the H/E ratio. Copyright © 2008 John Wiley & Sons, Ltd.
Surface modification, characterization and biofunctionality of pegylated titanate films obtained by the sol‐gel method
Authors: Pérez Mercedes Hernando , Noval Alvaro Muñoz , Navas Carmen Rodríguez , Silvan Miguel Manso , Torres‐Costa Vicente , Ceccone Giacomo , Ruiz Josefa P. García , Rossi Francois 
Published: January 2008

AbstractPegylated titanates have been prepared as biomedical supports in the form of thin films. The independent preparation of a polyethylene glycol (PEG) and a titanium isopropoxide (TIPT) precursor was followed by mixing at different molar ratios and spin casting onto Si (100) substrates to form the films. Activation of the hybrid structure was induced by annealing at temperatures right below the PEG melting point. Structural and compositional changes during these steps were followed by Fourier transformed infrared (FTIR) spectroscopy, XPS and water contact angle (CA) measurements. Biofunctionality of the pegylated titanates as antifouling ophthalmic films was tested on the one hand by determination of optical constants using genetic algorithms. On the other hand, indication of surface biocompatibility was provided by seeding mesenchymal stem cells. The results show that PEG‐rich surfaces are less biocompatible than mild inorganic surfaces as derived from the inhibition of cytoskeleton polarization. Copyright © 2008 John Wiley & Sons, Ltd.
Survismeter for simultaneous viscosity and surface tension study for molecular interactions
Authors: Singh Man 
Published: January 2008

AbstractSurvismeter simultaneously measures viscosities and surface tensions of several standard solvents (AR, methanol, ethanol, glycerol, ethyl acetate, n‐hexane, diethyl ether, chloroform, benzene, CCl4 and formic acid) and freshly prepared solutions of urea (U), 1‐methylurea (MU), 1,3‐dimethylurea (DMU) at several temperatures. Analysis for accuracies and hydrophobic interactions were made with data of solvents and solutions respectively. It replaces the use of viscometers and stalagmometer for viscosity and surface tensions individually. A decrease with one CH3 of MU and an increase with two CH3 of DMU in viscosities for 288.15–298.15 K with reverse trend for 303.15–308.15 K are noticed. Surface tension decreases from U to MU and increases with DMU at a slightly higher rate, but decreases with temperature. The CH3 is noticed to weaken hydrophilic interactions and strengthening hydrophobic interactions with stronger structure effecting changes in MU and DMU. Copyright © 2008 John Wiley & Sons, Ltd.
Physicochemical Characteristics of Starches of Two Sets of Near‐isogenic Wheat Lines with Different Amylose Content
Authors: Hung Pham Van , Yasui Takeshi , Maeda Tomoko , Morita Naofumi 
Published: January 2008

AbstractWheat lines with modified amylose content were produced by controlling the null alleles of three homoeologous Wx loci, Wx‐A1, Wx‐B1 and Wx‐D1 and those with triple‐null Wx alleles were found to yield waxy, amylose‐free starch. In this study, the new near‐isogenic lines developed by the recurrent backcross method between cv. Kanto 107 and the waxy mutant lines, K107Wx1 or K107Wx2, were cultivated and the physicochemical characteristics of their starches were investigated. The apparent amylose contents of the waxy near‐isogenic lines were 1.6 – 3.8%, whereas those of the non‐waxy near‐isogenic lines were 23.2 – 25.4%. The waxy lines had higher gelatinization temperature and enthalpy than the non‐waxy lines and no peak of amylose‐lipid complex as determined by DSC. The X‐ray diffraction patterns from both waxy and non‐waxy near‐isogenic lines corresponded to A‐type crystallization, like their parent lines. The starches isolated from the waxy lines had lower pasting onset and peak temperatures, higher peak viscosities and breakdown and lower final viscosity than those of the non‐waxy lines in the Viscoamylograph. The starch of non‐waxy near‐isogenic lines had lower peak and final viscosities and higher breakdown than did the recurrent parent line, cv. Kanto 107. The characteristics of the new wheat starches were well understood and classified, which will contribute to the wide application of these starches in food processing.
Using plasma acute-phase protein concentrations to interpret nutritional biomarkers in apparently healthy HIV-1-seropositive Kenyan adults
Authors: Thurnham David I. , Mburu Anne S. W. , Mwaniki David L. , Muniu Erastus M. , Alumasa Fred , de Wagt Arjan 
Published: January 2008

Inflammation influences the assessment of nutritional status. For example, inflammation reduces plasma retinol concentrations and vitamin A deficiency is overestimated. Conversely inflammation increases plasma ferritin concentrations and Fe deficiency is underestimated. Blood samples were obtained from 163 free-living HIV-1-infected adults, not on continuous medication, anti-retroviral drugs or micronutrients, not unwell and who had not reached WHO stage IV of HIV/AIDS. We used four markers of inflammation, C-reactive protein (CRP), α1-acid glycoprotein (AGP), α1-antichymotrypsin and erythrocyte sedimentation rate but mainly CRP and AGP were used to separate the subjects into four groups: ‘healthy’ where both CRP and AGP were normal; ‘incubation phase’ where CRP was elevated; ‘early convalescence’ where AGP and CRP were elevated and ‘late convalescence’ where only AGP was elevated. Correction factors were calculated to remove the influence of inflammation from each biomarker and group where inflammation was present and the data are shown before and after recalculation. The correction increased median plasma retinol concentrations of the whole group from 1·16 to 1·33 μmol/l, comparable with values (mean 1·29 μmol/l) in HIV-negative Kenyan women. Median ferritin concentrations fell by about 50 % in both sexes and the number of women with plasma ferritin concentrations ≤ 12 μg/l increased from eleven to twenty. The correction also increased plasma carotenoids and Hb but not α-tocopherol concentrations. We suggest that the method described to remove the influence of inflammation from nutritional biomarkers should be generally applicable in apparently healthy people and prevents discarding valuable data because of mild inflammation. The method does now need to be tested in other populations.