bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of iodine molecule adsorption on electronic properties of porous silicon studied by FTIR and EPR spectroscopy
Authors: Osminkina L. A. , Vorontsov A. S. , Kutergin S. A. , Tkachenko A. E. , Mamichev D. A. , Pavlikov A. V. , Konstantinova E. A. , Timoshenko V. Yu. , Kashkarov P. K. 
Published: May 2007

AbstractThe infrared absorption and electron paramagnetic resonance spectroscopy are used for studying the effect of adsorption of iodine (I2) molecules, strong acceptors of electrons, on the electronic properties of silicon nanocrystals in micro‐ and mesoporous silicon layers with different types of doping impurities. It is found that the concentration of free charge carries (holes) in silicon nanocrystals, obtained by electrochemical etching of p‐type and n‐type silicon wafers, sharply increases in the presence of I2 molecules. At the same time the decrease of the dangling silicon bonds (Pb‐centers) concentration is observed. A microscopic model proposed for explaining this effects presumes the formation of donor‐acceptor pairs (Pb1+‐I2–), and shallow acceptor states on the porous silicon surface which, together with the initial dopant and surface defect states, specify the charge carrier type and concentration in the silicon nanocrystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of ammonia adsorption on charge carriers in mesoporous silicon of n‐ and p‐type conductivity
Authors: Pavlikov Alexander V. , Osminkina Liubov A. , Vorontsov Alexander S. , Timoshenko Victor Yu. , Kashkarov Pavel K. 
Published: May 2007

AbstractInfrared spectroscopy is used to investigate the effect of ammonia adsorption on the concentration of equilibrium charge carriers in porous‐silicon layers with various initial types of dopants at different concentrations. It is found that ammonia adsorption from aqueous solution results in an increase in the concentration of free electrons in n ‐type samples up to a level exceeding 1018 cm–3. In p ‐type samples, a nonmonotonic dependence of the charge‐carrier concentration on ammonia pressure is observed. The obtained results are explained by the appearance of adsorption‐induced shallow donor states that, along with the initial‐dopant and surface‐defect states, determine the charge‐carrier type and concentration in the silicon nanocrystals of the porous layer after ammonia adsorption. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Detection of different states of water and oxide layer in porous silicon by IR spectroscopy
Authors: Korniyenko M. Ye. , Makara V. A. , Shevchenko V. B. , Korniyenko A. M. , Veblaya T. S. , Makhno M. M. 
Published: May 2007

AbstractDifferent states of water and oxide layer in porous silicon (PS) have been studied by IR spectroscopy method. The water states have been shown to depend on contact conditions between PS and condensed or vaporous forms of water and to determine all the variety of oxidation scenarios. Weakly‐ and strongly‐bonded water states are characterized by different frequencies of stretching bands νOH. Fine structure of absorption bands of oxygen‐silicon complexes (Si‐O‐Si, SiSiXO4–X) has been observed in the IR spectra. We associate it with fractal structure for thin oxide layers. Transition of fractal structure into nearly bulk SiO2 structure (where LO‐TO splitting is observed) with oxide layer thickness growth is considered. The oxide layer states are characterised by the intensity ratio of stretching to deformation bands for considered silicon‐oxygen complexes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of porous silicon oxidation on its behaviour in simulated body fluid
Authors: Pastor E. , Matveeva E. , Parkhutik† V. , Curiel‐Esparza J. , Millan M. C. 
Published: May 2007

AbstractThis work aims at studying of electrochemical oxidation of porous silicon (PSi) and its behaviour in simulated body fluid (SBF). Continuing electrochemical oxidation of PSi introduces gradual changes in morphology of the porous structure and composition of PSi. As a result, interaction between this material and SBF is changed. As more oxidized is the PSi sample, slower is the dissolution process (biodegradability) and more easily it becomes covered by the calcium‐phosphorous deposits from SBF (bioactivity). We observed that crystalline hydroxyapatite HA phase could be deposited in a very homogeneous manner onto OxPSi layers immersed in SBF at 36.5 °C during 30 days. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stabilization of nano‐crystalline porous silicon electroluminescence by high pressure water vapor annealing
Authors: Gelloz B. , Shibata T. , Koshida N. 
Published: May 2007

AbstractStabilization of electroluminescence (EL) from nanocrystalline porous silicon diodes has been achieved by using high pressure water vapor annealing (HWA) of nanocrystalline porous silicon (PS). HWA is performed at 260 °C and a pressure of 1.3 MPa. Devices treated by HWA show no degradation in EL intensity and diode current density under dc operation at constant voltage. The high stability is attributed to the high quality of the oxide surrounding the Si nanocrystals after HWA. This oxide is mostly unstrained and consists of a very uniform network. Furthermore, the Si/SiO2 interfacial defect density is very much reduced by HWA in comparison to that of conventional as‐prepared PS. The electrical characteristics of the diodes are also improved by HWA by reduced charge carrier trapping and charging. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical gain in oxidized porous silicon waveguides impregnated with a laser dye
Authors: Oton C. J. , Navarro‐Urrios D. , Ghulinyan M. , Capuj N. E. , González‐Pérez S. , Lahoz F. , Martín I. R. , Pavesi L. 
Published: May 2007

AbstractWe report positive optical gain under pulsed excitation in oxidized porous silicon planar waveguides impregnated with Nile Blue (LC 6900). Guided photoluminescence measurements show a dramatic line narrowing and a strong superlinear behaviour of the red emission when the pump power is increased. Variable stripe length (VSL) measurements show a clear transition from losses to gain, with a threshold of ∼3 mJ/cm2 at 700 nm. A maximum gain coefficient of 8.7 cm–1 is reported. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of hydrogen in the photoinduced evolution of porous silicon luminescence
Authors: Koropecki R. R. , Arce R. , Spies C. , Gennaro A. M. , Schmidt J. 
Published: May 2007

AbstractPhoto‐induced post preparation evolution effects in porous silicon were studied by IR, EPR, photoluminescence, and hydrogen effusion spectroscopies. The results show that two independent mechanisms are present during the photo‐induced evolution. We also show that hydrogen photo‐effusion takes place, in agreement with our previously proposed model. Photo‐effusion experiments performed in vacuum, combined with IR and photoluminescence spectroscopies allow to discriminate the competing mechanisms present in the evolution of the photoluminescence. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence from porous layers produced by Ag‐assisted electroless etching
Authors: Hadjersi T. , Gabouze N. 
Published: May 2007

AbstractPorous layers were formed on highly resistive p‐type silicon by an Ag‐ assisted electroless etching method using a chemical solution of HF and K2Cr2O7. The porous silicon (PS) layer formed by this method as a function of etching time was investigated by scanning electron microscopy (SEM) and backscattering spectrometry (BS) in random and channelling mode. Channelling spectra show that the porous layer remains crystalline after etching. On the other hand, random and channelling spectra show that the deposited silver diffuses into the pore. Luminescence from Ag‐assisted chemically etched layers was measured. It was found that the photoluminescence spectra strongly depend on etching time. Indeed, for etching time lower than 60 min, the PL emission is in the blue region with a peak located at 450 nm. In addition, for an etching time of 60 min or higher, the PL peak is centred at about 630 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence from porous layers formed on phosphorus‐implanted silicon by Ag‐assisted chemical etching
Authors: Gabouze N. , Hadjersi T. , Guerbous L. 
Published: May 2007

AbstractThe discovery of luminescence from porous silicon has stimulated intense and still increasing research activity. A great deal of effort has been devoted to study the photoluminescence from anodized ion‐implanted silicon. In the present work, we propose the metal‐assisted chemical etching method, using Na2S2O8 as oxidizing agent, to form photoluminescent porous layers on phosphorus implanted silicon. The properties of porous layers formed on implanted silicon as a function of doses and energies were investigated by scanning electron microscopy (SEM) and photoluminescence. The result shows that the PL spectra exhibit two principals emission bands centred at about 410 nm and 625 nm. In addition, it was shown that PL intensity corresponding to the red emission increases with increasing dose and energy. Finally, the changes in the PL spectrum are attributed to structural changes caused by both etching and ion implantation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light‐emission characteristics of silicon nanocrystals formed by anodization of bulk crystalline silicon in the transition regime
Authors: Gardelis S. , Nassiopoulou A. G. 
Published: May 2007

AbstractIn this study we report on the light‐emission characteristics of Si nanocrystals formed at the initial stages of anodization of bulk crystalline Si in the transition regime using extremely short pulses of anodic current. A considerable enhancement and a red‐shift of the photoluminescence (PL) peak of the as‐grown films under prolonged laser illumination in atmosphere was observed. Ageing or thermal oxidation in atmosphere at 300 °C caused similar red‐shift and significant enhancement of PL relative to the as‐grown films. In all cases the enhancement and the red‐shift of the PL coincided with the appearance of O2‐Si‐H2 and O2‐Si‐H(OH) stretching modes in the Fourier‐Transform‐Infra‐Red (FTIR) absorption spectra. Oxidation in dry oxygen at 900 °C caused red‐shift of PL without enhancement. Finally removal of the oxide caused blue shift of PL. All these observations are discussed in the context of the quantum confinement model. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient luminescence from rhodamine 6G absorbed by porous alumina: Excitation mechanisms
Authors: Moadhen A. , Elhouichet H. , Nosova L. , Oueslati M. 
Published: May 2007

AbstractPorous alumina (PA) samples are impregnated in rhodamine 6G (Rh6G) solution in order to form Rh6G/PA nanocomposites. The Fourier Transformer Infrared (FTIR) measurements show dispersion of dye molecules into the PA matrix. The investigations are focused on the photoluminescence (PL) properties and PL mechanisms in Rh6G/PA. We have discussed the effect of excitation beam wavelength on the PL spectrum of Rh6G/PA nanocomposite. It was found that the efficient luminescence of Rh6G/PA nanocomposite is governed by direct excitation and by dipolar interactions between Rh6G molecules with chemical species in alumina crystallites, as has been proved by FTIR measurements. An anti‐Stokes photoluminescence (APL) has been observed using a He‐Ne laser excitation. We show that its origin is related to a second order phenomenon where phonon absorption plays a key role. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Innovative electrochemical deep etching technique involving aluminum thermomigration
Authors: Kouassi S. , Gautier G. , Ventura L. , Semai J. , Boulmer‐Leborgne C. , Morillon B. , Roy M. 
Published: May 2007

AbstractA novel micro‐machining technique for silicon deep anisotropic etching and isolating porous silicon structure formation is developed in this paper. This method combines aluminum thermomigration through a N type silicon wafer and silicon electrochemical etching in a HF‐based solution. Using this technique, high aspect ratio trenches (1:5) and porous silicon isolating regions have been achieved through the entire thickness of the silicon wafers. Etch rate measurements have been performed varying the anodization current density. A maximum value of 22 µm.min–1 has been obtained. Moreover, the porosity behavior with the current density increase is also discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on porous silicon as electrode material in electrochemical capacitors
Authors: Desplobain S. , Gautier G. , Semai J. , Ventura L. , Roy M. 
Published: May 2007

AbstractIn this study, we have demonstrated the possibility of using macroporous silicon electrodes in electrochemical capacitors. Macroporous silicon was used to increase the surface exchange between pore surface and electrolyte. The inherent resistivity of the porous silicon can be reduced through the use of subsequent doping and metallization processes of the macropore surface. A systematic study of the electrolyte concentration and the porous silicon depth influences was also performed. A unit cell capacitance value of 320 µF/cm2 was obtained with doped and metallized p‐type macroporous silicon electrodes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous silicon surfaces for metabonomics: Detection and identification of nucleotides without matrix interference
Authors: Gómez D. , Fernández José Andrés , Astigarraga Egoitz , Marcaide Arrate , Azcárate Sabino 
Published: May 2007

AbstractIn present work, porous silicon surfaces (PSS) have been developed for time of flight mass spectrometric experiments (TOF‐MS) in the monitoring of nucleotides, commonly found as metabolites in the cell. The mass range of the studied molecules (∼ 400 amu) is common to several important messengers and other metabolites. Different porosified surfaces have been developed by means of electrochemical etching and different degree of porosity and pore size achieved as function of silicon dopant concentration, silicon resistivity, current density and the presence or absence of illumination along the process. As main conclusion, it can be said that an interesting commercial nucleotide (Cyclic adenosine monophosphate, c‐AMP) has been detected on low concentrations (∼hundreds of femtomols) for some of the fabricated porous surfaces. Taking into account that these concentrations are similar to the ones found in real samples, this result opens the possibility to the fabrication of DIOS (Desorption Ionization On Silicon) chips for the detection of nucleotides in biological fluids. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bruggeman effective medium approach for modelling optical properties of porous silicon: comparison with experiment
Authors: Khardani M. , Bouaïcha M. , Bessaïs B. 
Published: May 2007

AbstractWhile numerous works deal with the properties and applications of porous silicon (PS), some of the related topics are not complete or could be investigated from different aspects. The main objective of this paper is to provide novel information associated with the optical properties of nano‐ and meso‐PS by studying the variation of the effective refractive index (neff) and the relative dielectric constant (εr,eff) as a function of porosity. For this purpose various PS samples were prepared by electrochemical etching of p and p+‐type silicon wafers in order to form silicon supported nano‐PS and free‐standing meso‐PS layers, respectively. The experimental effective optical parameters (neff, εr,eff) of the meso‐PS films, were determined from the transmission spectra and the Bragg law. While, in the case of nano‐PS layers, we applied the Goodman method, and deduced the values of neff and εr,eff from the Bruggeman's effective medium approximation (EMA). In the EMA calculation, the PS structure was considered as being a physical combination of three distinct phases formed by silicon, silicon dioxide and voids with a convenient volume fraction. A good agreement between theory and experiment was found in the case of silicon‐supported nano‐PS for all porosities. However, for free‐standing meso‐PS, the theory does not well fit the experimental results for porosities lower than 50% and higher than 70%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of surface in light induced degradation of porous silicon
Authors: Mandal N. P. , Kumar Abhishek , Agarwal S. C. 
Published: May 2007

AbstractExposure of porous silicon (PS) to moisture is found to increase its photoluminescence (PL) intensity, whereas it decreases drastically upon light soaking. On the other hand, coating by a thin layer of polystyrene protects PS against light induced degradation without changing PL significantly. Further, polystyrene coating protects the PS from humidity also. FTIR shows appearance of new bonding configurations at the PS/polymer interface, whcih may account for the improved stability. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of surface roughness for ARXPS
Authors: Oswald S. , Oswald F. 
Published: May 2007

AbstractAngle‐resolved X‐ray photoelectron spectroscopy (ARXPS) is a method for non‐destructive depth profiling in the nm thickness range. For the quantification of the data, usually model calculations are used which approximate the surface structures by smooth layers. Using ARXPS data from a computer simulation, in this paper we study the influence of overlayer roughness on the quantification results. It can be followed, that rough overlayers modeled by means of small‐sized islands are identified nearly as smooth layers. The effective thickness, however, can be evaluated always satisfactorily. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth studies of Ta‐based films on Si with STM and XPS
Authors: Zahn W. , Oswald S. , Fülle A. , Hildebrand D. , Zier M. , Wetzig K. 
Published: May 2007

AbstractThe aim of the experiments was the characterization of the first stages of film growth on silicon substrates with scanning tunneling microscopy (STM) and angle‐resolved X‐ray photoelectron spectroscopy (ARXPS). Thin Ta films were deposited in situ by magnetron sputtering onto Si in the thickness range from less than one monolayer up to 10 nm. The results of the experiments show a formation of tantalum silicide at the interface to the substrate. The local current‐voltage characteristics obtained by scanning tunneling spectroscopy (STS) measurements show that the first stages of tantalum silicide growth are characterized by island formation. The in situ STM results are in good agreement with those of the ARXPS investigations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of FeO films on SrTiO3(100)
Authors: Heinrich B. , Demund A. , Szargan R. 
Published: May 2007

AbstractDepending on different annealing steps (100 °C to 800 °C) and the pretreatment of the substrate, we investigated the chemical and morphological state of ultra thin FeO films on SrTiO3(100) by XPS and LEED. Two types of pretreated substrates were used: (A) SrTiO3, annealed at 600 °C and (B) SrTiO3, annealed at 800 °C. While (A) showed no change in colour, (B) became blue due to oxygen vacancies in the bulk. We found, that annealing of SrTiO3 in UHV influences the reactivity of the contact FeO/SrTiO3. Depending on the pretreatment, approximately 50% of FeO were reduced to Fe at different temperatures ((A): T = 300 °C; (B): T = 200 °C). During annealing reduced Ti(IV) species, such as Ti(III, II and 0), occurred only in the case of preannealing at 800 °C (B). LEED investigations showed the rearrangement of the deposited films starting from 600 °C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gas phase and bulk photoemission spectra of highest occupied molecular orbitals of pi‐conjugated organic molecules
Authors: Sauther J. , Wüsten J. , Lach S. , Ziegler Ch. 
Published: May 2007

AbstractThe highest occupied molecular orbital (HOMO) of the pi‐conjugated organic molecule 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA) was investigated via bulk and gas phase ultraviolet photoemission spectroscopy. As a result of the absence of various photoemission linewidth broadening effects which occur in the case of condensed matter, the measurements on single molecules allow an estimate of the contributions of these effects to the total linewidth. Distinctive peaks resulting from vibrational excitations can be recognized and thus a comparison with other spectroscopy methods is possible. Furthermore, spectra of the HOMOs of 1,4,5,8‐naphthalene‐tetracarboxylic dianhydride (NTCDA) and 1,8‐naphthalene‐dicarboxylic anhydride (NDCA) were also recorded and compared to the results for PTCDA, showing a decrease in linewidth with decreasing molecule size. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Use of focused ion beam sample preparation for Auger analysis
Authors: Scheithauer U. 
Published: May 2007

Abstract FIB cross‐sections are often used to get access to sample features of interest. Due to the inherent surface sensitivity an AES measurement is favourable for small feature compositional analysis on such samples. Even though the primary electron beam diameter of a modern field emission AES instrument is about 30 nm and thereby nearly ten times that of a SEM, the analysis volume of an AES measurement is much smaller than that of SEM/EDX. As AES measurements on small sample features can last for many hours it is mandatory to compensate a likely mechanical drift. In this procedure at regular intervals SE images are compared with an SE image recorded at the beginning of the measurement. Lateral drifts are compensated by an additional electrostatic deflection of the primary beam. For this purpose on low contrast samples or samples with periodically repetitive structures a FIB crater cut into the sample surface can be successfully applied as a marker feature to determine sample drift. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Induction and analysis of cell adhesion and differentiation on inkjet micropatterned substrates
Authors: Blau A. , Ugniwenko T. 
Published: May 2007

AbstractIn the context of interfacing biological entities to technical substrates, proof of principle results on patterning cell culturing substrates by inkjet deposition of the cell adhesion mediator polyethyleneimine are presented. Pattern fidelity, cell adhesion, and cell differentiation of chick neurons and glia cells on such interfaces were evaluated microscopically. The exemplary results demonstrate that piezo inkjet printing of biologically active compounds has the potential of becoming an easy to handle and versatile strategy for applying a wide variety of substances in any combination and concentration with cellular to subcellular resolution onto a wide selection of substrates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elemental imaging mass spectrometry of thin sections of tissues and analysis of brain proteins in gels by laser ablation inductively coupled plasma mass spectrometry
Authors: Becker J. Sa. , Zoriy M. , Becker J. Su. , Dobrowolska J. , Dehnhardt M. , Matusch A. 
Published: May 2007

AbstractLaser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) has become established as a very efficient and sensitive trace and surface analytical technique in the life sciences. We applied LA‐ICP‐MS to produce images for investigating the spatial element distribution as well as the layered structures and inhomogeneities in thin tissue sections (e.g., human and rat brain tissues). In order to quantify the analytical data, matrix‐matched laboratory standards were prepared and analyzed by applying the optimized experimental parameters using LA‐ICP‐MS. Furthermore, the possibility of the nanometer‐scale analysis of elements on sample surfaces by near‐field LA‐ICP‐MS on soft matter (e.g., on 2D gels and biological samples) will be discussed briefly. This novel technique opens up a new challenging path for future applications in the quantitative imaging of elements in life sciences and nanotechnologies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)