bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulsed laser annealing of semiconductor structures for functional devices
Authors: Misra N. , Xu L. , Rogers M. S. , Ko S. H. , Grigoropoulos C. P. 
Published: July 2008

AbstractWe review our progress on the laser processing of semiconductor microstructures and nanostructures for functional devices. Fundamental research conducted to understand the melt‐mediated phase transformations induced by nanosecond laser irradiation in thin semiconductor films is presented. A detailed experimental study analyzed the physical mechanisms of the explosive crystallization in amorphous germanium that produces large area self‐sustained crystal growth. The double laser crystallization method that combines a nanosecond laser pulse and a modulated microsecond laser beam was shown to produce ultra‐large grain polycrystalline silicon, enabling fabrication of thin film transistor devices of high performance from amorphous silicon films. The crystal growth process was imaged by temporally resolved photography. Non‐melt Excimer Laser annealing of thin silicon‐on‐insulator films for dopant activation was demonstrated. Applying multiple laser pulses below the melting threshold effected solid phase annealing of the single crystalline silicon films. Semiconductor nanowires are one‐dimensional nanostructures that have displayed the potential to be used with low‐cost flexible plastic substrates for applications such as large‐area displays and sensor arrays. The excimer laser annealing of silicon nanowires is demonstrated as an alternative to conventional thermal annealing for dopant activation. The optical absorption of the nanowires is discussed and the effect of parameters such as fluence and number of pulses is investigated. The interaction of laser pulses with silicon nanowires is investigated through numerical simulations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excimer laser beam/ITO interaction: from laser processing to surface reaction
Authors: Legeay G. , Castel X. , Benzerga R. , Pinel J. 
Published: July 2008

AbstractWe investigated interactions between UV light and Indium Tin Oxide (ITO) thin films sputtered at room temperature. Owing to their photon energy, higher than the band gap of In2O3 (3.5–4.0 eV), KrF (5.0 eV) or XeCl (4.0 eV) lasers proved useful, at high fluences (1‐3 J/cm2) for minute laser shaping, at low fluences (100 mJ/cm2) for laser annealing, or even at very low fluences for gases desorption. Sputtered ITO becomes totally amorphous when an oxygen flow is mixed in the process argon and adjusted for the lowest resistivity. As non optimised layers behave like gas sensors, amorphous ITO is immune to atmospheric agents. The band structure of indium oxide and exposures to UV light at selected wavelengths helped to a better understanding of the gas sensing mechanisms on oxygen rich and oxygen poor layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fixed charge density distribution on pulsed laser deposited high‐k oxide layers
Authors: Ratzke M. , Yang B. , Reif J. 
Published: July 2008

AbstractWe report on Scanning Kelvin Probe Microscopy of thin praseodymium oxide layers produced by pulsed laser deposition on silicon substrates. These measurements allow an almost direct quantification of the charge state of both interface and bulk of the films. Surprisingly, we find an apparent change in the charge distribution as a result of exposing the structure to ambient air: Immediately after deposition, negative charges are trapped at the interface between film and silicon substrate, and positive charges in the film bulk. After exposure to ambient air for about a week, a dramatic change of surface potentials is observed, including the sign of the charges.Whereas the influence of growth related parameters like film thickness on the surface potential by can be easily investigated, the role of ageing under ambient conditions is, presently, by far not understood. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multicrystalline silicon films with large grains on glass: preparation and applications
Authors: Andrä Gudrun , Falk Fritz 
Published: July 2008

AbstractPolycrystalline silicon films on glass with grain sizes exceeding 10 µm by far are of growing interest for thin film solar cells as well as for TFTs in flat panel displays. Grains as large as this arise preferably from solidification of the melt. The most successful method for preparing such films is laser melting and crystallization of amorphous silicon, which may be deposited at temperatures well below the softening point of glass substrates. By making use of a laser the silicon melting time can be short enough as not to damage the substrate. Moreover, by using an appropriate laser irradiation process, a temperature regime can be chosen so as to influence the nucleation rate and growth kinetics to get grain sizes over 100 µm in size. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low frequency noise in polysilicon thin film transistors: effect of the laser annealing of the active layer
Authors: Pichon L. , Boukhenoufa A. , Cordier C. 
Published: July 2008

AbstractLow‐frequency noise is studied in N‐channel polysilicon TFTs issued from two (low temperature ≤600 °C) technologies: furnace solid phase crystallized (FSPC) and laser solid phase crystallized (LSPC) TFTs. The distribution of the trap states (DOS) into the polysilicon bandgap determined for devices biased in the weak inversion is one decade lower for LSPC devices. The high range values (10–4 ≤ α ≤ 1) of the measured macroscopic noise parameter, defined according to the Hooge empirical relationship, are explained by the drain current crowding due to structural defects within the active layer. The higher values of α for the LSPC TFTs are attributed to a better structural quality of the active layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Laser‐induced self organization of silicon–germanium hillocks for field emission displays
Authors: Weizman M. , Nickel N. H. , Sieber I. , Yan B. , Fostiropoulos K. 
Published: July 2008

AbstractWe report here on the formation of a self‐organized hillock structure in polycrystalline silicon–germanium (SiGe) thin films with a Ge content of 30 to 70%, due to the irradiation of the films with a sequence of laser pulses. By varying the crystallization parameters it is possible to control the periodicity length of the structure from 0.4 to 2 µm. The self organization phenomenon can be switched on and off by using substrates with different thermal conductivities. In addition, we show that the self‐organized hillock structure exhibits a low field emission threshold of 20 V/µm and therefore has an immense potential for field emission displays. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
KTa0.5Nb0.5O3ferroelectric thin films grown by pulsed laser deposition: structural characteristics and applications to microwave devices
Authors: Moussavou A.‐G. , Députier S. , Perrin A. , Sauleau R. , Castel X. , Legeay G. , Benzerga R. , Mahdjoubi K. , Guilloux‐Viry M. 
Published: July 2008

AbstractIn this paper, we report on KTN ferroelectric thin films grown by Pulsed Laser Deposition on various substrates suitable for microwave applications and the agility of CPW stub resonators operating in X‐band printed on these films. The ferroelectric material selected here is KTa0.5Nb0.5O3(KTN). X‐ray characterizations and scanning electron microscopy re‐ vealed an epitaxial growth on MgO and LaAlO3substrates, while films deposited on sapphire were textured. Measurements have demonstrated a tunability reaching 5% for KTN/sapphire and 1% for KTN/MgO‐LaAlO3. The resonators have also been characterized in terms of quality factor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pulsed laser deposition with excimer lasers
Authors: Delmdahl R. , Pätzel R. 
Published: July 2008

AbstractProgress in material research and processing industry is fueled by the technique of pulsed laser deposition (PLD). High energy excimer lasers enable this technique since every material is amenable to their high photon energies. Spectral properties, temporal pulse and laser beam parameters of state of the art excimer lasers will be compared with frequency converted Nd:YAG lasers. Both quality and longevity of the deposited layers strongly depend on the degree of accuracy achieved in the thin film ablation and subsequent deposition process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excimer‐laser induced structural transformations of TiO2 thin films
Authors: Van Overschelde O. , Boisdequin J. M. , Leclère Ph. , Wautelet M. 
Published: July 2008

AbstractThin films of TiO2 are deposited by magnetron sputtering on glass substrate and are irradiated by UV radiation using a KrF excimer laser (λ = 248 nm). The present works deals with the ablation regime. In order to characterize the structural transformations occurring in the process, the morphology of the films are studied as a function of the laser fluence (F), by means of profilometry and atomic force microscopy (AFM). As deposited films are measured to be amorphous. After one pulse, when the laser fluence, F, is varied, various regimes are observed. We show thanks to this process, it is possible to remove a layer in a predefined thickness by choosing F. More over, we observe a linear dependence of the ablated depth with F. It is shown that the morphology of the surfaces depends strongly of F, as evidenced from AFM images, roughness measurements and the fractal dimension. In order to interpret these results, temperature evaluations are performed. The ablation rate may not be explained by purely thermal effects. It is argued that electronic effects play a major role in excimer‐laser induced structural transformations of TiO2 thin films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pulsed‐laser deposition of ZnO thin‐films on MgO substrates
Authors: Friedrich F. , Sieber I. , Klaus M. , Genzel Ch. , Nickel N. H. 
Published: July 2008

AbstractZinc oxide thin‐films were grown by laser deposition technique on (111)‐ and (100)‐oriented magnesium oxide substrates (MgO). The deposition temperature was varied between 600 and 860 °C. In this temperature range the formation of Mg(OH)2 is thermodynamically unfavorable which prevents a degradation of the MgO surface. The films were characterized by scanning electron microscopy, Raman spectroscopy, and X‐ray diffraction. The results show that high‐quality c‐axis oriented ZnO thin‐films were grown on (111)‐oriented MgO. On (100)‐oriented MgO a more complex ZnO thin‐film formation was observed. At lower growth temperatures grains of different orientation were identified. Grains with orientations that deviated from (001) contain more residual stress, which manifests itself in a shift of the E2high phonon mode position to 442 cm–1. With increasing growth temperature the film structure becomes more uniform and at 860 °C large areas of either (001) or (101) orientation were found. The results also indicate that no amorphous ZnO buffer layer is formed at the interface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of composition and structure of ferroelectric oxide thin films grown by pulsed laser deposition
Authors: Guilloux‐Viry Maryline , Peng Wei , Députier Stéphanie , Bouquet Valérie , Perrin André 
Published: July 2008

AbstractSrBi2Nb2O9 and KTa1–xNbxO3 high quality thin films were grown by pulsed laser deposition. An accurate optimization of deposition conditions is a prerequisite for the control of composition, mainly according to the high volatility of Bi and K. In order to take benefit of the ferroelectric characteristics for new microelectronic devices, thin films were epitaxially grown on various substrates and seed layers adapted to application requirements. For that purpose metal electrodes and ferroelectric oxides were associated in a planar capacitor geometry or in a coplanar configuration depending on the targeted applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature and moist‐stability effects on midlatitude orographic precipitation
Authors: Kirshbaum Daniel J. , Smith Ronald B. 
Published: July 2008

AbstractIdealized, convection‐resolving simulations of moist orographic flows are conducted to investigate the influence of temperature and moist stability on the drying ratio (DR), defined as the fraction of the impinging water mass removed as orographic precipitation. In flow past a long ridge, where most of the air rises over the barrier rather than detouring around it, DR decreases as the surface temperature (Ts) increases, even as the orographic cap cloud becomes statically unstable at higher Ts and develops embedded convection. This behaviour is explained by a few physical principles: (1) the Clausius–Clapeyron equation dictates that the normalized condensation rate decreases as the flow gets warmer, (2) the replacement of ice‐phase precipitation growth with warm‐rain processes decreases the efficiency by which condensate is converted to precipitation, thereby lowering precipitation efficiency, and (3) embedded convection acts more to vertically redistribute moisture than to enhance precipitation. Over an isolated mountain, the effects of (1) and (2) are counteracted by moisture deflection around the barrier, which is stronger in the colder, more stable flows. Copyright © 2008 Royal Meteorological Society
Quantification of key red blood cell folates from subjects with defined MTHFR 677C>T genotypes using stable isotope dilution liquid chromatography/mass spectrometry
Authors: Huang Yuehua , Khartulyari Stefanie , Morales Megan E. , Stanislawska‐Sachadyn Anna , Von Feldt Joan M. , Whitehead Alexander S. , Blair Ian A. 
Published: July 2008

AbstractRed blood cell (RBC) folate levels are established at the time of erythropoiesis and therefore provide a surrogate biomarker for the average folate status of an individual over the preceding four months. Folates are present as folylpolyglutamates, highly polar molecules that cannot be secreted from the RBCs, and must be converted into their monoglutamate forms prior to analysis. This was accomplished using an individual's plasma pteroylpolyglutamate hydrolase by lysing the RBCs in whole blood at pH 5 in the presence of ascorbic acid. Quantitative conversion of formylated tetrahydrofolate derivatives into the stable 5,10‐methenyltetrahydrofolate (5,10‐MTHF) form was conducted at pH 1.5 in the presence of [13C5]‐5‐formyltetrahydrofolate. The resulting [13C5]‐5,10‐MTHF was then used as an internal standard for the formylated forms of tetrahydrofolate that had been converted into 5,10‐MTHF as well any 5,10‐MTHF that had been present in the original sample. A stable isotope dilution liquid chromatography‐multiple reaction monitoring/mass spectrometry method was validated and then used for the accurate and precise quantification of RBC folic acid, 5‐methyltetrahydrofolate (5‐MTHF), tetrahydrofolate (THF), and 5,10‐MTHF. The method was sensitive and robust and was used to assess the relationship between different methylenetetrahydrofolate reductase (MTHFR) 677C>T genotypes and RBC folate phenotypes. Four distinct RBC folate phenotypes could be identified. These were classified according to the relative amounts of individual RBC folates as type I (5‐MTHF >95%; THF <5%; 5,10‐MTHF <5%), type II (5‐MTHF <95%; THF 5% to 20%; 5,10‐MTHF <5%), type III (5‐MTHF >55%; THF >20%; 5,10‐MTHF >5%), and type IV (5‐MTHF <55%; THF >20%; 5,10‐MTHF >5%). Copyright © 2008 John Wiley & Sons, Ltd.
Structural characterization and identification of ecdysteroids from Sida rhombifolia L. in positive electrospray ionization by tandem mass spectrometry
Authors: Wang Yan‐Hong , Avula Bharathi , Jadhav Atul N. , Smillie Troy J. , Khan Ikhlas A. 
Published: July 2008

AbstractSeven ecdysteroids isolated from Sida rhombifolia L. were studied by electrospray ionization multi‐stage tandem mass spectrometry (ESI‐MSn) in the positive ion mode using an ion trap analyzer and high‐performance liquid chromatography coupled with a diode‐array detector (HPLC/DAD). The HPLC experiments were performed by means of a reversed‐phase C18 column and a binary mobile phase system consisting of water (containing 0.05% formic acid) and acetonitrile (containing 0.05% formic acid) under gradient elution conditions. According to mass spectral features and the substitution at C‐2, C‐20, C‐24 and C‐25, ecdysteroids in S. rhombifolia were classified into three sub‐groups. Structural identification of these three sub‐groups of ecdysteroids was established by LC/multi‐stage ion trap mass spectrometry on‐line or off‐line. The fragmentation patterns of ecdysteroids yielded ions of successive loss of 1–4 water molecules. Furthermore, ions corresponding to the complete loss of the side chain at C‐17 will help to identify the sub‐groups of ecdysteroids in addition to containing a hydroxyl moiety at one of the above‐mentioned positions. Based on the HPLC retention behavior, the diagnostic UV spectra and the molecular structural information provided by ESI‐MSn spectra, a total of nine naturally occurring ecdysteroids were identified, of these two are identified for the first time in S. rhombifolia. Copyright © 2008 John Wiley & Sons, Ltd.
Hydrogen/deuterium exchange on protein solutions containing nucleic acids: utility of protamine sulfate
Authors: Poliakov Anton , Jardine Paul , Prevelige Peter E. 
Published: July 2008

AbstractObtaining global hydrogen/deuterium (H/D) exchange data on proteins is an important first step in amide proton exchange experiments. Important information such as the mode of exchange, the cooperativity of folding/unfolding reactions, and the effects of ligand binding can be readily obtained in global exchange experiments. Many interesting biological systems are complexes containing both proteins and nucleic acids. The low pH conditions required to quench H/D exchange reactions result in the formation of stable protein/nucleic acid precipitates which interfere with the liquid chromatography step of the experiment and preclude obtaining mass spectrometric data. In this work we show that the precipitation of proteins and nucleic acids is electrostatic in nature and can be prevented by high ionic strength and by removing nucleic acids by protamine sulfate. Using protamine sulfate in quenching solution, we were able to obtain global H/D data with protein samples containing large amounts of DNA or RNA. Copyright © 2008 John Wiley & Sons, Ltd.
Investigation of norflurazon pesticide photodegradation using plasma desorption time‐of‐flight mass spectrometry analysis
Authors: Thomas J.‐P. , Bejjani A. , Nsouli B. , Gardon A. , Chovelon J.‐M. 
Published: July 2008

AbstractWe have previously demonstrated that PD‐TOFMS (plasma desorption time‐of‐flight mass spectrometry) analysis is a powerful technique for the in situ analysis of pesticides deposited or adsorbed on solid materials. With the aim of producing reproducible data on the modification of a pesticide under controlled photodegradation conditions, we have now undertaken a study where both the substrate and the pesticide are well characterized. This is the case for norflurazon deposited onto an aluminium substrate, in particular regarding the reproducibility of preparation of the samples and the change with time of their chemical composition. Degradation parameters have been derived from the variation in yield of ions representative of the molecule and of its breakdown products and, particularly, from the time required for 50% dissipation of their initial concentration (DT50). DT50 values ranging between 1 and 10 h have been found. An interpretation of the degradation process is proposed from the decay of other ions. As expected, the degradation is faster when the UV sunlight is unfiltered (a factor of 3.8 for the molecule, and around 5 for the breakdown products). Copyright © 2008 John Wiley & Sons, Ltd.
Metabonomics investigation of human urine after ingestion of green tea with gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry and 1H NMR spectroscopy
Authors: Law Wai Siang , Huang Pei Yun , Ong Eng Shi , Ong Choon Nam , Li Sam Fong Yau , Pasikanti Kishore Kumar , Chan Eric Chun Yong 
Published: July 2008

AbstractA method using gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and 1H NMR with pattern recognition tools such as principle components analysis (PCA) was used to study the human urinary metabolic profiles after the intake of green tea. From the normalized peak areas obtained from GC/MS and LC/MS and peak heights from 1H NMR, statistical analyses were used in the identification of potential biomarkers. Metabolic profiling by GC/MS provided a different set of quantitative signatures of metabolites that can be used to characterize the molecular changes in human urine samples. A comparison of normalized metabonomics data for selected metabolites in human urine samples in the presence of potential overlapping peaks after tea ingestion from LC/MS and 1H NMR showed the reliability of the current approach and method of normalization. The close agreements of LC/MS with 1H NMR data showed that the effects of ion suppression in LC/MS for early eluting metabolites were not significant. Concurrently, the specificity of detecting the stated metabolites by 1H NMR and LC/MS was demonstrated. Our data showed that a number of metabolites involved in glucose metabolism, citric acid cycle and amino acid metabolism were affected immediately after the intake of green tea. The proposed approach provided a more comprehensive picture of the metabolic changes after intake of green tea in human urine. The multiple analytical approach together with pattern recognition tools is a useful platform to study metabolic profiles after ingestion of botanicals and medicinal plants. Copyright © 2008 John Wiley & Sons, Ltd.
Quantitative analyses of fullerene and polycyclic aromatic hydrocarbon mixtures via solvent‐free matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Cristadoro Anna , Räder Hans Joachim , Müllen Klaus 
Published: July 2008

AbstractWe explore the feasibility of reliable quantitative matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) analyses via solvent‐free sample preparation, as this procedure provides the unique convenience of being applicable also to insoluble samples. As quantitative MALDI measurements are even more complicated for species ionized by cation attachment, we investigated model systems, such as polycyclic aromatic hydrocarbons (PAHs) and fullerenes, which undergo photoionization and do not require additional cationizing salts. Our quantitative approach rests upon applying the standard‐addition method in MALDI for the quantitative characterization of binary mixtures. Two different systems are tested. Set 1 is composed of hexakis(dodecyl)hexabenzocoronene and hexakis(dodecyl)hexaphenylbenzene, which represent the product and precursor of a cyclodehydrogenation reaction, and Set 2 is a mixture of C60 and C70 fullerenes. In Set 1, severe anomalies could be detected due to a strong influence of the matrix/analyte ratio on the correlation between signal intensity and analyte amount. This can be related to the strong intermolecular interactions among the hexabenzocoronene (HBC) aromatic cores hampering the desorption step and to intermolecular charge transfers, which influence the ionization probability. Minor interferences to the quantitative MALDI characterization are encountered in the analysis of C60 and C70 fullerenes. The spherical shapes of C60 and C70 buckyballs prevent strong aggregation. Thus, no molecule‐dependent anomalies in their desorption‐photoionization behaviour are recognized. Copyright © 2008 John Wiley & Sons, Ltd.