bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dependence of the singlet oxygen photosensitization efficiency on morphology of porous silicon
Authors: Ryabchikov Yu. V. , Belogorokhov I. A. , Vorontsov A. S. , Osminkina L. A. , Timoshenko V. Yu. , Kashkarov P. K. 
Published: April 2007

AbstractWe investigate the effect of oxygen molecule adsorption on the photoluminescence of porous silicon films of different porosity. The experimental results are explained by the photosensitization of singlet oxygen generation due to the energy transfer from excitons confined in Si nanocrystals to O2 molecules adsorbed on the Si nanocrystal surface. The energy transfer time and photosensitization efficiency are found to depend on porosity of the samples. The singlet oxygen generation efficiency increases strongly for porous silicon with high (>80%) porosity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrochemical pore etching in Ge – An overview
Authors: Fang C. , Föll H. , Carstensen J. , Langa S. 
Published: April 2007

AbstractWhile electrochemical pore etching in semiconductors has become a thriving field for research (and applications) in the past 15 years or so, little work has been done in Ge. Besides Si, Ge is the only semiconductor with a diffusion length large enough to enable the use of backside illumination, which has proved to be the decisive “trick” for the formation of excellent macropores in Si, and experiments in this vein have been conducted. However, Ge proved to behave in rather unexpected ways – the large body of pore etching knowledge obtained with Si and the III–V's was not directly applicable to Ge. While no good pores could be produced in most previous endeavours including our own, we finally succeeded in producing deep pores in n‐type but also in p‐type Ge of various doping levels and crystal orientations. A host of new and not yet totally understood phenomena was discovered. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon nanofibers encapsulated in macropores in silicon
Authors: Starkov V. , Red'kin A. 
Published: April 2007

AbstractThis work reports on the development of fuel cells electrodes with a porous silicon structure and carbon nanofibers encapsulated in macropores in silicon. It is demonstrated that decomposition of carbon on a Ni catalyst deposited on the pore walls can be used to create a homogeneous carbon nanotube layer that dramatically increases the specific surface area while simultaneously reducing the resistivity of the macroporous silicon layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous silicon as an internal reflector in thin epitaxial solar cells
Authors: Kuzma‐Filipek I. , Duerinckx F. , Van Nieuwenhuysen K. , Beaucarne G. , Poortmans J. , Mertens R. 
Published: April 2007

AbstractThin film epitaxial silicon solar cells are considered a near future alternative to bulk silicon solar cells. However due to the limited thickness of the active layer they require efficient light trapping. Therefore we propose the development and implementation of such light confinement by means of a porous silicon (PS) intermediate reflector at the epi/substrate interface. The formation of the reflector is done by electrochemical etching of a highly doped Si substrate into a multilayer stack (Bragg‐optical reflector), and is followed by epitaxial deposition of the active layer. The implementation of the PS reflector however requires detailed analysis of many problematic issues, foremost the optical optimisation of the stack for internal reflection at the Si/PS/Si interface. Other topics include the pore rearrangement during high‐temperature CVD as well as the quality of the epitaxial layer grown on porous silicon. Another challenge is the resistance within the PS layers. For that purpose, SRP (Spreading Resistance Probe) and resistance measurements were performed to determine the conductive properties of rearranged PS. First cells with a 9‐layer porous silicon reflector gave a very promising efficiency of 13.5% which is 1.5% higher compared to cells without internal reflector. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vapor control of resonant Zener tunneling of light in a photonic crystal
Authors: Ghulinyan M. , Gaburro Z. , Wiersma D. S. , Pavesi L. 
Published: April 2007

AbstractWe show a vapor controlled one‐dimensional photonic crystal built with a silicon‐based dielectric mesoporous material, in which the refractive index can be continuously tuned by flowing organic vapors through the pores. Exposure of the crystal to vapors induces an inhomogeneous change in the refractive index through the depth and results in a tilted photonic band structure. We drive the photonic crystal to the optical Zener breakdown condition, introducing an enhanced transmission channel through the crystal. This phenomenon closely resembles the electronic Zener breakdown in a reverse‐biased p–n junction. The effect is reversible and opens new perspectives for physics in photonic crystals and novel device concepts based on sensing, switching and processing of light. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of photogenerated carriers in porous silicon probed by microwave absorption
Authors: Porteanu H. E. 
Published: April 2007

AbstractWe report on dynamics of photogenerated carriers in porous silicon using contactless investigation tools. A comparison of two theoretical models: the simple point charge description versus degenerate gas model is presented. The temperature dependence reveals the dominant role of surface states below 70 K. Light intensity dependences evidence Auger processes. The optical and chemical properties can be indirectly improved using the microwave conductivity by studying the surface states of porous materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
p+–n diodes with a lateral porous layer as gas sensors
Authors: Barillaro G. , Diligenti A. , Strambini L. M. 
Published: April 2007

AbstractIn this work an integrated p+–n diode, diffused on a crystalline substrate and provided with a thin adsorbing porous layer, is proposed as gas sensor. The sensor can be easily integrated by using an industrial CMOS process due to the fact that the porous film formation is the last process step. The sensitivity to isopropanol vapors has been investigated by measuring both the forward and reverse current of the diode as a function of the vapor concentration. The current variations, up to two orders of magnitude, could be explained by assuming that the adsorption of molecules in the porous layer and their interaction with localized states modify the band structure of the crystalline diode at the interface with the porous silicon, and in turn its current. Another sensor feature is that the value of the reverse current variation, induced by isopropanol vapors, depends on the voltage, so that the sensitivity can be settled by simply changing the reverse voltage itself. The fabrication process, the static and dynamic behavior of the sensor are presented and discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of Pd layer on the sensitivity of CHx/PS/Si as structure for H2 sensing
Authors: Gabouze N. , Cheraga H. , Belhousse S. , Ghellai N. , Zouadi N. , Ouadah Y. , Chabane‐Sari N.‐E. 
Published: April 2007

AbstractIn this work, a hydrogen sensor based on Palladium/hydrocarbons (CHx )/Porous silicon/Silicon structure has been studied in presence of hydrogen gas. Current–voltage characterizations show that the sensitivity of the sensor is improved by more than two orders of magnitude compared with the uncoated CHx /PS/Si device. In addition, a rapid response time of the sensor of about 10 s is measured. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CMOS‐compatible fabrication of porous silicon gas sensors and their readout electronics on the same chip
Authors: Barillaro G. , Bruschi P. , Pieri F. , Strambini L. M. 
Published: April 2007

AbstractIn this work, integration on the same chip of porous silicon gas sensors along with their driving/readout electronic circuits by using an industrial microelectronic process is demonstrated. To ensure maximum compatibility, the porous silicon formation is performed after the integrated circuit fabrication flow is completed. The chip contains three CMOS operational amplifiers, a band‐gap voltage reference, an integrated temperature sensor and several porous silicon‐based NO2 sensors. The simultaneous functionality of the electronics and the sensor is demonstrated by using various circuit blocks to implement a simple driving/readout electronic interface for the sensor. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrochemical fabrication of buried folded microchannels into silicon substrates
Authors: Barillaro G. , Nannini A. , Piotto M. 
Published: April 2007

AbstractIn this work an original process for buried folded silicon microchannel fabrication is reported. Electrochemical micromachining is exploited to etch high aspect ratio meander‐shaped trenches into a silicon substrate. Thermal oxidation is then employed to seal the top of etched trenches and obtain buried microchannels at the bottom. The process is straightforward and allows the integration of buried folded channels into silicon substrates with a high density. Experimental results are reported and advantages and drawbacks of the proposed process are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrically enhanced erosion of porous Si material in electrolyte by pH modulation and its application in chronotherapy
Authors: Leong W. Y. , Loni A. , Canham L. T. 
Published: April 2007

AbstractWe have studied the enhanced erosion of porous Si material in the vicinity of a cathodic electrode during electrolysis of tap water and simulated gastric or intestinal fluids. This enhanced erosion is attributed to the pH increase (more alkaline) near the cathode due to a local depletion of the [H+] species during the electrolysis of water. The effect provides a means of electrically controlling drug release from the porous Si structures useful in chrono‐therapeutic applications. We have described the concept and prototype of a self‐contained electronic time‐controlled drug delivery capsule system suitable for oral administration or implantation into the body. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Waveguiding, absorption and emission properties of dye‐impregnated oxidized porous silicon
Authors: Navarro‐Urrios D. , Ghulinyan M. , Capuj N. E. , Oton C. J. , Riboli F. , Martín I. R. , Pavesi L. 
Published: April 2007

AbstractThe waveguiding, absorption and emission properties of oxidised porous silicon waveguides when impregnated with Nile Blue have been studied. We present m‐line measurements before and after the impregnation showing that the effective indices of the modes remain the same. When performing guided luminescence experiments, a structured emission band is measured. Using the refractive index profile extracted from m‐line measurements it has been possible to simulate the emission lineshape assuming the observation of an interference pattern formed across the waveguide. We demonstrate that these oscillations appear because in the first hundreds of nanometers the dye concentration is several orders of magnitude higher than in the rest of the sample. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cathodoluminescence and photoluminescence of individual silicon nanowires
Authors: Dovrat M. , Arad N. , Zhang X. H. , Lee S. T. , Sa'ar A. 
Published: April 2007

AbstractPhotoluminescence (PL) spectroscopy and Cathodoluminescence (CL) spectroscopy and imaging have been utilized to resolve red and blue emission bands from silicon nanowires. We have found that the blue emission band comes from local defects in the silicon dioxide shell of the wires while the red band comes from interfaces between the silicon dioxide shell and the crystalline silicon core. Time‐resolved PL spectroscopy of hydrogen‐ and oxygen‐terminated silicon nanowires, indicates that surface chemistry plays an essential role in determining the luminescence properties of the nanowires. We suggest that the PL lifetime should be related to nonradiative relaxation processes that take place at the interface of the silicon core and the clad material of the nanowires. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence properties of the porphyrin/porous silicon composites
Authors: Chirvony V. S. , Bolotin V. L. , Ovejero J. , Matveeva E. S. , Dzhagarov B. M. , Albella J. , Parkhutik V. P. 
Published: April 2007

AbstractA study of luminescence properties of water‐soluble and hydrophobic porphyrin and chlorin molecules immobilized in oxidized (i.e. non‐luminescent) and as‐prepared (i.e. luminescent) porous silicon (porSi) layers is carried out. It is found that the oxidized porSi matrix itself does not introduce any quenching effect on the porphyrin fluorescence, but the fluorescence is subjected to the concentration quenching. At maximum porphyrin/chlorin concentration used (ca. 10–3 M in impregnation solutions) the quenching is strong in case of hydrophobic porphyrins and sufficiently moderate for water‐soluble ones, especially for cationic porphyrin TMPyP4. A concentration of the latter in porSi layer is determined by direct measurements. Both hydrophobic and water‐soluble porphyrins immobilized on the surface of as‐prepared porSi are found to quench the luminescence of the latter. In case of hydrophobic porphyrins the quenched porSi luminescence is regained almost to the initial value on the time scale of tens of hours, whereas in case of water‐soluble porphyrins the fluorescence spectrum of the latter builds up in course of time. Possible mechanisms responsible for these effects are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical study of acoustic band‐gap structures made of porous silicon
Authors: Reinhardt A. , Snow P. A. 
Published: April 2007

AbstractIn this paper, we discuss the acoustic properties of porous silicon and outline the differences and similarities of the behaviour of elastic and light waves in mesoporous porous silicon etched in p+‐type silicon wafers. We then investigate the expected acoustic characteristics of distributed Bragg mirrors and rugate filters obtained by a modulation of porosity with depth. In particular, we emphasize some features these mirrors exhibit when compared to the optical equivalents in pSi. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic and inhomogeneous Coulomb screening in the Thomas–Fermi approximation: Application to quantum dot–wetting layer system and Auger relaxation
Authors: Even J. , Cornet C. , Doré F. 
Published: April 2007

AbstractA model for anisotropic and inhomogeneous Coulomb screening due to 2D and 3D carriers, is proposed in the Thomas–Fermi approximation. Analytical expressions for the screened interaction potentials and scattering matrix elements are obtained. This model is applied to the Auger relaxation of carriers in an InAs/InP quantum dot (QD) – wetting layer (WL) system. The influences of the QD morphology and carriers densities on screening and Auger effects are studied. 2D–2D scattering is found to be the most important process, depending especially on QD morphology. A smearing effect is associated to the wetting layer wavefunction extension along the growth axis. The screened potential is similar to a potential screened by 3D carriers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monte Carlo calculation of Ising model with single‐site anisotropy energy in ferromagnetic iron nitride system
Authors: Liu Junyou , Zhang Lanting , Shan Aidang 
Published: April 2007

AbstractThe magnetic behavior of a mixed Ising ferromagnetic system on Fe4N expended face‐center cubic lattice, with single‐site anisotropy, has been studied with Monte Carlo Simulation. The expended face‐center cubic lattice was divided into one simple cubic lattice composed of Fe(I) at the corner site and three inhomogeneous simple cubic lattices composed of Fe(II) at the face‐centered one. The two sublattices have spin‐3/2 and spin‐1, respectively. The model includes nearest interactions and single‐site anisotropy terms. By studying magnetization, internal energy, specific heat of this model at different temperatures, we found that the absolute zero value of magnetization is changed by existence of Fe(I)'s and Fe(II)'s crystal‐field interactions (D1,D2). The final value of internal energy is different for differentD1andD2. Curie temperature is increasing with the increase ofD1andD2. Especially, equal point of sublattice magnetization was recognized, whenD1was changed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron orderings in the (hard‐core) boson–fermion model
Authors: Sidowski M. , Robaszkiewicz S. 
Published: April 2007

AbstractThe system of coexisting local pairs and itinerant electrons described by the (hard‐core) boson–fermion model is analysed, taking into account both the intersubsystem charge exchange coupling I0 as well as the density–density interaction V0. In our preliminary report [Acta Phys. Pol. A 109, 647 (2006)] we have shown within an extended mean‐field approach that at T = 0 the model considered can exhibit not only the superconducting (SC) but also the charge density wave (CDW) phases as well as the so called charge Kondo state (CKS), which is characterised by a compensation of a local charge moment (isospin singlet). Here we shortly conclude those findings and present several new results concerning this subject. In particular the mutual stability of various phases, including the mixed ordered state (SC‐CKS) is analysed and the effects of the deviation from half‐filling on the properties of the system are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural transition control of laterally overgrown c‐GaN and h‐GaN on stripe‐patterned GaAs (001) substrates by MOVPE
Authors: Sanorpim S. , Takuma E. , Ichinose H. , Katayama R. , Onabe K. 
Published: April 2007

AbstractGrowth mechanisms and material quality of the laterally overgrown cubic‐phase gallium nitride (c‐GaN) and hexagonal‐phase gallium nitride (h‐GaN) on stripe‐patterned GaAs (001) substrates were investigated using transmission electron microscopy (TEM). Investigational results show that h‐GaN is only laterally overgrown along the (111)B facets of the c‐GaN stripes with the growth direction of (0001)h‐GaN//(111)B c‐GaN for all the mask stripe orientations. Dislocation density in the laterally overgrown h‐GaN regions for the [110]‐stripe pattern is reduced to be lower than 104 cm–2, which is six orders of magnitude smaller than that in the conventionally grown h‐GaN films. On the other hand, the laterally overgrown c‐GaN with lower planar defect (stacking faults and twins) density presents in the region just above the stripe windows for the [1$ \bar 1 $0]‐stripe pattern. In addition, a large reduction of planar defect density was found in the laterally overgrown c‐GaN regions for the [100] stripe direction. Also, a model is used to describe the cubic‐to‐hexagonal structural transition in lateral‐overgrown GaN on patterned GaAs (001) substrates for the purpose of lower dislocation and lower planar defect densities in the laterally overgrown h‐GaN and c‐GaN, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependencies of high‐temperature reduction on conversion products and their isotopic signatures
Authors: Leuenberger Markus C. , Filot Marc S. 
Published: April 2007

AbstractHigh‐temperature reduction (HTR) is widely used for oxygen and hydrogen isotope determination. Decomposition of cellulose, sucrose and polyethylene foil by HTR is quantitative for temperatures around 1450°C. For lower reaction temperature production of CO2, water and the deposition of carbon inside the reactor are significant and thus the element of interest for isotopic analysis is split into different pools, leading to isotope fractionation. After reduction of cellulose or sucrose at 1125°C less than 60% of the oxygen is found as CO, which is monitored with the isotope ratio mass spectrometer to determine the δ18O value. The remaining oxygen is unevenly distributed between CO2 and H2O, preferentially as CO2. Raising the reaction temperature to 1425°C yields almost quantitative conversion of oxygen into CO and results in a 3‰ more positive δ18O value. Similarly, only 40–50% of the carbon of cellulose and sucrose is transformed into CO in the HTR reactor at 1125°C. This is far from the stoichiometric expected value of 83% for quantitative carbon transfer for cellulose and 92% for sucrose. Of the carbon 40–50% is deposited in the reactor and the remainder can be found as CO2. Based on the comparison of carbon isotope results from HTR and those obtained from combustion, we hypothesize that CO produced during the HTR originates partly from sample carbon and glassy carbon. A combined combustion and HTR carbon isotope determination may provide an insight into the intramolecular carbon distribution of organic substances. These results suggest that HTR should be carried out at temperatures above 1450°C to make sure that fractionations associated with the reduction process are minimal. If this is not possible frequent calibration is required using reference materials of the same structure as the sample. Copyright © 2007 John Wiley & Sons, Ltd.
Understanding the building blocks of dynamic systems
Authors: Cronin Matthew A. , Gonzalez Cleotilde 
Published: April 2007

AbstractWe report three empirical studies intended to clarify why individuals misperceive the relationships between stocks and flows. We tested whether familiarity with the problem type, motivation to solve the problem, or the graphical presentation of the problem affected participants' understanding of stock and flow relationships. We conclude that the misperceptions of stocks and flows are a pervasive and important problem in human reasoning. Neither the domain familiarity nor increased motivation helped individuals improve their perception of stock and flow relationships; but it seems that the graphical representation directs attention to flows and not stocks, setting the stage for subsequent mistakes. Individuals attend to the most salient points of a graph rather than comprehending the overall accumulation over time. Future research needs to investigate several aspects of the problem representations, such as the use of physical or textual rather than graphical representations. Copyright © 2007 John Wiley & Sons, Ltd.
Dynamics of climate policy
Authors: Fiddaman Thomas 
Published: April 2007

AbstractThis article is based on the talk I delivered at the 2006 International System Dynamics Conference in Nijmegen, upon receiving the Jay W. Forrester Award for Exploring policy options with a behavioral climate–economy model (Fiddaman, 2002). Here I attempt to step back from modeling particulars, to talk about the global policy context of climate change. In particular, it appears to me that a great deal of effort is misdirected toward policies that are unlikely to achieve significant mitigation of climate change. Redirecting that effort toward practical policies requires a shift in the regulatory paradigm of policymakers and the mental models of the public. System dynamics is well positioned to contribute some of the innovations needed to make that shift happen. Copyright © 2007 John Wiley & Sons, Ltd.