bluuebunny/crossref_metadata_2025_split huggingface dataset:
N‐type doping of InGaN by high energy particle irradiation
Authors: Yu K. M. 
Published: March 2009

AbstractThis article reviews our extensive studies of the effects of native defects introduced by high energy particles on the electrical and optical properties of InGaN alloys. We show that the electronic properties of irradiated InGaN can be well described by the amphoteric defect model. Because of the extremely low position of the conduction band edge of InN the formation energy of native donor defects is very low in In‐rich InGaN alloys. High energy particle irradiation of InN and In‐rich InGaN, will therefore produce donor defects and result in more n‐type materials. As the irradiation dose increases, the electron concentration increases until the Fermi energy EF approaches the Fermi stabilization energy EFS. At this point both donor and acceptor‐type defects are formed at similar rates, and compensate each other, leading to stabilization of EF and a saturation of the electron concentration. Hence a large increase and then saturation in the Burstein–Moss shift of the optical absorption edge is also observed. Furthermore we also found that mobilities in the irradiated films can be well described by scattering from triply charged defects, providing strong evidence that native defects in InN are triple donors. The excellent agreement between the experimental results and predictions based on the ADM suggests that particle irradiation can be an effective and simple method to control the doping (electron concentration) in In‐rich Inx Ga1–x N via native point defects. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐ and three‐dimensional composite photonic crystals of macroporous silicon and lead sulfide semiconductor nanostructures
Authors: Gutman Nadav , Armon Akiva , Osherov Anna , Golan Yuval , Sa'ar Amir 
Published: March 2009

AbstractWe describe a new method for direct deposition and growth of nanocyrstalline lead sulfide (PbS) thin films into two‐ and three‐dimensional arrays of macroporous silicon and the formation of composite silicon photonic crystals (PhCs). Infrared transmission measurements exhibit a substantial red‐shift of the photonic stop bands from the composite PhCs relative to the PhC substrates. Photoluminescence spectroscopy reveals the effect of slow‐light modes on the emission spectra from PbS thin films inside a two‐dimensional PhC. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reusable linking chemistry for His‐6 tagged proteins in an affinity‐based porous silicon biosensor
Authors: Bonanno Lisa , DeLouise Lisa 
Published: March 2009

AbstractThe inexpensive fabrication and intrinsic optical and filtering properties of porous silicon (PSi) make optical PSi biosensors ideally suited for diagnostic testing. Long term goals of a diagnostic sensor would benefit from reversible binding chemistry to allow retesting of patient samples and collection of captured target for analysis. This work illustrates a versatile method to immobilize hexahistidine (His‐6) tagged molecular probes and utilizes reversible competitive chelating chemistry to reuse the porous silicon sensor device. Reuse of this Ni–His‐6 chemistry in a PSi affinity‐based biosensor was demonstrated with two different His‐6 tagged proteins to give consistent probe loading values within mimimal error over 4 cycles of use. Advantages of utilizing any site‐directed immobilization method include the homogeneity of surface bound probe molecule orientation, which we also illustrate resulted in a 2‐fold increase in detection capability of a secondary target antibody. As the current sensitivity range of macroporous PSi sensors (diameters of 30–100 nm) pose limitations to their use in medical applications; this work identifies the ability to improve target capture through the development of an efficient and versatile linking chemistry. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of porous anodic alumina templates in selected micrometer‐sized areas on a Si substrate. Application for growing ordered Ti nanopillars
Authors: Gianneta V. , Huffman M. , Nassiopoulou A. G. 
Published: March 2009

AbstractThe local formation of porous anodic alumina (PAA) thin films on confined areas measuring few μm2 through an SiO2 masking layer on the silicon substrate has been developed. The locally grown porous anodic alumina thin films showed highly symmetric vertical cylindrical pores with a pore density that was much higher than that of films on non‐confined areas. Pore density as high as 6 × 1010 pores/cm2 was achieved, compared to ∼1010 pores/cm2 in corresponding large‐area samples. Pore diameter was as small as 30–50 nm. Alumina thin films on confined areas on a Si substrate are very interesting for use as masking layers for local Si nanopatterning or as templates for local growth of different nanostructures, e.g. nanowires of different materials, on wafer level. In this work, we used the PAA films as sacrificial templates to grow locally on a silicon wafer using sputtering, regular arrays of Ti nanopillars on pre‐selected areas on the Si wafer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Location‐dependent controlled release kinetics of model hydrophobic compounds from mesoporous silicon/biopolymer composite fibers
Authors: Fan Dongmei , Loni Armando , Canham Leigh T. , Coffer Jeffery L. 
Published: March 2009

AbstractIn this study, biodegradable mesoporous Si (BioSiliconTM) was loaded with cis‐(2,2′‐bipyridine) dichlororuthenium (II) (Ru complex) as a model hydrophobic compound. This ruthenium complex‐loaded BioSiliconTM was either partially embedded on the surface of electrospun polycaprolactone (PCL) fibers or fully encapsulated within the fibers. To study release profiles in the above model delivery systems, porous Si/PCL constructs were soaked in DI water at 37 °C and the UV–Vis absorption spectrum of the supernatant was measured as a function of time. These results show that the Ru complex was released in a sustained manner over 7‐day period. In addition, it is shown that the controlled‐release of this complex depends on both the spatial location of the complex in the PCL fibrous scaffolds as well as the amount of Ru compound loaded in the mesoporous Si. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subwavelength inhomogeneities in Cu(In,Ga)Se2 thin films revealed by near‐field scanning optical microscopy
Authors: Gütay Levent , Pomraenke Robert , Lienau Christoph , Bauer Gottfried Heinrich 
Published: March 2009

AbstractWe have analyzed Cu(InGa)Se2 thin films, fabricated by standard deposition technique for solar cells, by near‐field scanning optical microscopy (NSOM) which allows for simultaneous detection of photoluminescence (PL) and AFM‐like topography. In comparison with our former confocal microscopy studies this approach yields a lateral optical resolution of ≈200 nm which is substantially below the diffraction limit. The sample is investigated by a fiber probe which guides the laser excitation to the sample surface and collects the PL signal. The recorded scans show significant lateral variations of the PL yield on length scales of 0.2–1.5 μm. By applying Planck's generalized law we extract lateral variations of the splitting of quasi‐Fermi levels Δ(EFn–EFp) and optical threshold energies ΔEop,th (band gap) in the absorber. We find substantial lateral variations of these properties with ΔFWHM(EFn–EFp) ≈ 17 meV (FWHM: full width half maximum), ΔFWHM(Eop,th) ≈ 18 meV and ΔFWHM(thickness) ≈ 220 nm. While no significant correlation between local surface topography and PL yield or Δ(EFn–EFp) is observed, we find a clear anticorrelation between the optical threshold energies and the recorded height signal. Our results extend previous studies of inhomogeneity effects on solar cell absorbers towards the 100 nm regime. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impurity vibration modes in II–VI and III–V mixed semiconductors
Authors: Postnikov Andrei , Pagès Olivier , Souhabi Jihane , Nassour Ayoub , Hugel Joseph 
Published: March 2009

AbstractThe analysis of vibration frequencies in dilute semiconducting alloys is addressed, as part of a more vast paradigm for the description of lattice dynamics in semiconductor alloys within the “1 bond – 2 mode” concept. Specific cases considered are those of Be impurities in ZnSe (system with high elastic contrast; aspects of impurity clustering) and of (Ga,In)As alloys, exhibiting much smaller elastic contrast and almost vanishing value of the mode splitting parameter, Δ. First‐principles calculations of frequencies are done by Siesta method, using 64‐atom supercells. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Se activity and its effect on Cu(In,Ga)Se2photovoltaic thin films
Authors: Contreras Miguel A. , Repins Ingrid , Metzger Wyatt K. , Romero Manuel , Abou‐Ras Daniel 
Published: March 2009

AbstractWe study some physical properties of CuIn1–xGaxSe2thin‐films fabricated by evaporation from elemental sources under various Selenium environments. Specifically, thin‐films were fabricated under growth conditions such as Se deficiency, near stoichiometry and excess Se during coevaporation to investigate the impact of the Se environment on absorber film properties and ultimately the device performance. We determine the chemical activity of Se in the evaporation process has a strong influence on film macrostructure (prefered orientation) and microstructure, particularly at the grain and grain boundary level. It is shown that the optoelectronic properties at grain boundaries are affected by the Se environment used resulting in absorber thin‐films with distictive defect distribution and defect density. Consequently, the performance of the solar cells fabricated from those films is also affected by the Se environment. These effects on solar cell performance and absorber properties are reported in a (i) structural analysis of the CuIn1–xGaxSe2/Mo/glass samples by X‐ray and electron backscattering techniques; (ii) optolectronic radiative characteristics of the absorbers by cathode luminescence and photoluminescence studies and (iii) current–voltage, quantum efficiency and capacitance–voltage measurements for the solar cells made from the absorbers fabricated under the pre prescribed Se growth conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Use of contactless electroreflectance in the development of quantum cascade lasers from ZnCdSe/ZnCdMgSe
Authors: Muñoz Martin , Tamargo Maria C. 
Published: March 2009

AbstractElectro‐modulation techniques have been used extensively to analyze interband transitions in materials and devices, however little has been done to use these techniques for the analysis of intersubband transitions in materials and devices. In this work, contactless electroreflectance has been used to determine the conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures. Toward the development of quantum cascade lasers, multi‐quantum well structures with intersubband absorption at 178 meV were analyzed using contactless electro‐reflectance. Finally, quantum cascade laser structures were designed for emission at 4.8 μm. The multi‐quantum well structures presented an excellent agreement between the designed and measured absorption and emission, respectively. This work demonstrates that contactless electro‐reflectance can accurately determine the conduction band offset and is useful in the analysis of intersubband transitions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of polarization‐dependent photoreflectance studies for c ‐plane GaN films grown on a ‐plane sapphire
Authors: Röppischer Marcus , Goldhahn Rüdiger , Buchheim Carsten , Furtmayr Florian , Wassner Thomas , Eickhoff Martin , Cobet Christoph , Esser Norbert 
Published: March 2009

AbstractThe optical properties of c ‐plane GaN layers grown by molecular beam epitaxy on a ‐plane sapphire substrate are investigated. Polarization‐dependent photoreflectance spectroscopy was applied with the electric field vector of the probe beam being either parallel or perpendicular to the [10$ \bar 1 $0] direction of the GaN films. A pronounced in‐plane optical anisotropy under normal incidence of light is observed which is attributed to anisotropic in‐plane strain. It originates from the difference of the thermal expansion coefficients of the substrate parallel and perpendicular to its c‐axis. Temperature‐dependent studies and a comparison to photoluminescence and reflectance anisotropy studies indicate that the strain (anisotropy) increases with decreasing sample temperature. The dependence of transition energies and oscillator strengths of GaN as a function of strain values is calculated by k·p perturbation theory for comparison. The results emphasize the experimental data. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Piezoreflectance and photoreflectance study of annealing effects on GaAs0.916Sb0.084 and GaAs0.906Sb0.075N0.019 films on GaAs grown by gas‐source molecular beam epitaxy
Authors: Hsu H. P. , Huang Y. N. , Huang Y. S. , Lin Y. T. , Ma T. C. , Lin H. H. , Tiong K. K. , Sitarek P. , Misiewicz J. 
Published: March 2009

AbstractThermal annealing effects of GaAs0.916Sb0.084 and GaAs0.906Sb0.075N0.019 films grown on GaAs substrates by gas‐source molecular beam epitaxy have been characterized by piezoreflectance (PzR) and photoreflectance (PR). By a comparison of relative intensity of PzR and PR spectra, the identification of conduction to heavy‐hole (HH) band and conduction to light‐hole (LH) band transitions originated from the strained induced valence band splitting have been achieved. The near band edge transition energies are blue‐shifted, and the splitting of HH and LH bands is reduced after thermal annealing treatment. The annealing effects of GaAs0.906Sb0.075N0.019 are found to be more pronounced than that of GaAs0.916Sb0.084. The temperature dependences of near band edge transition energies are analyzed using Varshni and Bose–Einstein expressions in the temperature range from 15 K to 300 K. The parameters that describe the temperature variations of the near band edge transition energies are evaluated and discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of ultra‐high pressure sterilization on the structure of polymer films
Authors: Fairclough J. P. A. , Conti M. 
Published: March 2009

AbstractThe effect of ultra‐high‐pressure processing on the structure of polymer film pouches, commonly used in food packaging, has been studied. In particular, the effect of an air headspace on the polypropylene heat‐sealing inner layer is reported. With increasing pressure, both nitrogen and oxygen gases become increasingly soluble in the polymer layer. If the pressure is rapidly released, this causes voids and pits to form in the inner layer. An estimate of the increased solubility (70‐fold) is calculated from regular solution theory. Copyright © 2009 John Wiley & Sons, Ltd.
Theoretical studies on redox properties, protonation sites, and electronic spectrum of a new type of polyoxometalate [Ti12Nb6O44]10− by DFT
Authors: Si Yan‐Ling , Chen Wei‐Lin , Wang En‐Bo 
Published: March 2009

AbstractThe electronic structure of a new type of polyoxometalate [Ti12Nb6O44]10− has been investigated using density functional theory (DFT). The calculations represent that the LUMO in fully oxidized [Ti12Nb6O44]10− delocalizes among the titanium (Ti) and niobium (Nb). Therefore, both Ti and Nb have the probability to accept extra electron when [Ti12Nb6O44]10− as catalyst is reduced, which has been reinforced by the spin density for the monoreduced specie [Ti12Nb6O44]11−. Three kinds of possible protonated isomers [HTi12Nb6O44]9− are discussed. The results reveal that the preferred protonation sites correspond to bridging oxygens NbOTi. In addition, the calculation of electronic spectrum shows that there is an obvious intramolecular charge transfer from oxygen to metal. The solvent effects were also considered in the calculations by using a conductor‐like screening model (COSMO) of solvation with the solvent‐excluding surface. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Implementation and benchmark tests of the DFTB method and its application in the ONIOM method
Authors: Zheng Guishan , Lundberg Marcus , Jakowski Jacek , Vreven Thom , Frisch Michael J. , Morokuma Keiji 
Published: March 2009

AbstractWe present the theoretical and implementation details of the DFTB method with analytical gradients into the Gaussian package. SCF optimization performance with DIIS method is compared with modified Broyden method and Anderson methods, from which DIIS method is to be preferred. The number of geometry optimization steps can be significantly decreased with the Berny algorithm compared to the conjugated gradient method. From the comparison of geometry parameters as well as trends in the change of HOMO and LUMO energies, the results show clearly that DFTB can reproduce values obtained at the B3LYP/6‐31G(d) level well. We also investigated the DFTB method as the low level quantum mechanical (QM) method in an ONIOM (QM:QM′) description for an amino acid model system and found DFTB promising as a method to describe polarization and charge‐transfer effects in large systems. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Charge conducting properties of hydrated DNA duplex between Au electrodes obtained by molecular simulations and Green's function theory
Authors: Tsukamoto Takayuki , Wakabayashi Hajime , Sengoku Yasuo , Kurita Noriyuki 
Published: March 2009

AbstractThe dependence of charge conducting properties through DNA‐duplex + Au‐electrode systems on DNA base sequence, DNA conformation, structure of Au electrodes, and solvating water molecules was investigated by using molecular simulations and Green's function theory. The simulated results indicate that the conducting properties depend most strongly on the structure of Au electrodes. It is also clarified that the charge conductance through DNA duplex is largely affected by the conformational change of DNA and the structure of connection between DNA‐duplex and Au electrodes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
The chemiionization reactions Ce + O and Ce + O2: Assignment of the observed chemielectron bands
Authors: Todorova Tanya K. , Infante Ivan , Gagliardi Laura , Dyke John M. 
Published: March 2009

AbstractMulticonfigurational quantum chemical methods (CASSCF/CASPT2) have been used to study the chemiionization reactions Ce + O → CeO+ + e− and Ce + O2 → CeO + e−. Selected spectroscopic constants for CeOn and CeO (n = 1, 2), as well as reaction enthalpies of the chemiionization reactions of interest, have been computed and compared with experimental values. In contrast to the lanthanum case, for both Ce + O2(X3Σ) and Ce + O2( a1Δg), the Ce + O2 → CeO + e− reaction is shown to be exothermic, and thus, contributes to the experimental chemielectron spectra. The apparent discrepancy between the computed reaction enthalpies and the high kinetic energy offset values measured in the chemielectron spectra is rationalized by arguing that chemielectrons are produced mainly via two sequential reactions (Ce + O2 → CeO + O, followed by Ce + O → CeO+ + e−) as in the case of lanthanum. For Ce + O2 (a1Δg), a chemielectron band with higher kinetic energy than that recorded for Ce + O2( X3Σ) is obtained. This is attributed to production of O( 1D) from the reaction Ce + O2( a1Δg) → CeO + O( 1D), followed by chemiionization via the reaction Ce + O( 1D) → CeO+ + e−. Accurate potential energy curves for the ground and a number of excited states of CeO and CeO+ have been computed, and a mechanism for the chemiionization reactions investigated experimentally was proposed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Quantum and classical vibrational relaxation dynamics of N‐methylacetamide on ab initio potential energy surfaces
Authors: Fujisaki Hiroshi , Yagi Kiyoshi , Straub John E. , Stock Gerhard 
Published: March 2009

AbstractEmploying extensive quantum‐chemical calculations at the DFT/B3LYP and MP2 level, quartic force fields of isolated N‐methylacetamide are constructed. Taking into account 24 vibrational degrees of freedom, the model is employed to perform numerically exact vibrational configuration interaction calculations of the vibrational energy relaxation of the amide I mode. It is found that the energy transfer pathways may sensitively depend on details of the theoretical description. Moreover, the exact reference calculations were used to study the applicability and accuracy of (i) the quasiclassical trajectory method, (ii) time‐dependent second‐order perturbation theory, and (iii) the instantaneous normal mode description of frequency fluctuations. Based on the results, several strategies to describe vibrational energy relaxation in biomolecular systems are discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Efficient parallel algorithm of second‐order Møller–Plesset perturbation theory with resolution‐of‐identity approximation (RI‐MP2)
Authors: Katouda Michio , Nagase Shigeru 
Published: March 2009

AbstractAn efficient parallel algorithm is developed for second‐order Møller–Plesset perturbation theory with the resolution‐of‐identity approximation of two‐electron repulsion integrals (RI‐MP2) to perform MP2 energy calculations of large molecules on distributed memory processors. Benchmark calculations are carried out for taxol (C47H51NO14), valinomycin (C54H90N6O18), and two‐layer nanographene sheets (C96H24)2, which show the high parallel efficiency of the developed algorithm. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
On the construction of Kramers paired double group symmetry functions
Authors: Peng Daoling , Ma Jianyi , Liu Wenjian 
Published: March 2009

AbstractRelativistic quantum chemical calculations on molecular systems can greatly be expedited by making use of the full molecular symmetry, including both double point group and time‐reversal symmetry. A simple yet general scheme is proposed here to make double point group symmetry functions also form Kramers pairs such that the resulting operator matrices have the desired structure (i.e., quaternion, complex, or real). The key idea is to insert appropriate phase factors into the symmetry functions or make a suitable unitary transformation of them. Arbitrary finite double point groups can be handled in the same way. As for a product basis, the same symmetrization can be achieved by simple modifications of the vector coupling (Clebsch–Gordan) coefficients. This is especially of interest to, e.g., time‐dependent relativistic density functional linear response theory or relativistic two‐electron repulsion integral evaluations in general. Several examples are provided to illustrate the algorithm and its efficiency. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009