bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Performance Polymer Thin Film Transistors Array Printed on a Flexible Polycarbonate Substrate
Authors: Park Sung Kyu , Han Jeong In , Moon Dae Gyu , Kim Won Keun , Kim Yong Hoon 
Published: April 2011

ABSTRACTHigh performance poly (3-hexylthiophene) (P3HT) thin film transistors (TFTs) array was fabricated on a polycarbonate substrate by micro-contact printing method. A thin polyimide layer (40 nm) was applied before silicon oxide deposition to improve the electrical properties of the TFT device. Also, the effects of O2 plasma treatment on the field effect mobility and output current behaviors of the devices were investigated. By plasma treatment, the surface roughness of gate dielectric was improved which accounts for the increased field effect mobility and the hole Schottky barrier height in electrode/semiconductor interface was lowered resulting in large drain current in the device. Based on the experiments, we fabricated P3HT TFTs array with 0.025 cm2/V·s in saturation field effect mobility and on/off current ratio of 103 ∼ 104 on a polycarbonate substrate.
Kondo-excitons and Auger processes in self-assembled quantum dots
Authors: Govorov A. O. , Karrai K. , Warburton R. J. , Kalameitsev A. V. 
Published: April 2011

ABSTRACTWe describe theoretically novel excitons in self-assembled quantum dots interacting with a two-dimensional (2D) electron gas in the wetting layer. In the presence of the Fermi sea, the optical lines become strongly voltage-dependent. If the electron spin is nonzero, the width of optical lines is given by kBTK, where TK is Kondo temperature. If the spin is zero, the exciton couples with the continuum due to Auger-like processes. This leads to anticrossings in a magnetic field. Such states can be called Kondo-Anderson excitons. Some of the described phenomena are observed in recent experiments.
Long-Lifetime Nonlinear Absorption of PbS Quantum Dots
Authors: Huang Feiran , Filin Aleksey , Rao Pratima G.N. , Doremus Robert H. , Persans Peter D. 
Published: April 2011

ABSTRACTWe have fabricated PbS particles in glass of average size from 1.2 nm to 3 nm. This allows us to tune the energy of the lowest electron-hole pair transition from 1.7 eV to 0.8 eV respectively. Optical absorption spectra show a pronounced quantum peak, implying a narrow size distribution. We have performed pump-probe spectroscopy where the probe is cw and the pump is nanosecond; this allows us to investigate a wide time scale. We have observed bleaching of the lowest quantum peak with lifetimes of ∼2 microseconds. We interpret this in terms of trapped carriers. Phenomenological description of observed effect is also presented.
Resonant Raman Scattering by Strained and Relaxed Ge Quantum Dots
Authors: Milekhin Alexander G. , Nikiforov Alexander I. , Ladanov Mikhail , Pchelyakov Oleg P. , Tenne Dmitri A. , Schulze Steffen , Zahn Dietrich R.T. 
Published: April 2011

ABSTRACTFundamental vibrations in Ge/Si structures with strained and relaxed Ge quantum dots (QDs) grown by molecular beam epitaxy were investigated using resonant Raman spectroscopy. Transmission electron microscopy experiments show that the strained Ge QDs are typical “hut clusters” with base size of 15nm and a height of 2nm. A two mode distribution in size (100–200nm and 3–6nm) is found for relaxed QDs. The Raman efficiencies of the Ge optical phonons as a function of excitation energy reveal maxima at 2.35–2.41eV attributed to the E0 resonance in Ge QDs due to electronic confinement. The frequency positions of optical phonons localized in Ge “hut clusters” under non-resonant conditions correspond to fully strained Ge QDs while the frequency position of optical phonons in relaxed Ge QDs corresponds to the value in bulk Ge. With increasing excitation energy (2.5–2.7eV) the position of the Ge optical phonons shifts downwards due to size-confinement effect of optical phonons in strained and relaxed Ge QDs, indicating the presence of a QD size distribution in Ge dot structures.
Optical Detection of the Charging of InAs Quantum Dots with Different Backgate Configurations
Authors: Su B. , Karsten L. , Schüller C. , Heitmann D. , Zhukov A. A. , Heyn Ch. , Hansen W. 
Published: April 2011

ABSTRACTWe investigate self-assembled InAs quantum dots by photoluminescence (PL) and capacitance spectroscopies. By employing specially designed backelectrode configurations, we can control the number of electrons, which are confined in the quantum dots. With PL experiments we study the dependence of the s-s transition on the electron occupation of the quantum dots. We observe a characteristic redshift of the s-s transition when the s-shell is filled with electrons. However, if the p-shell of the quantum dots starts to fill, the samples with different backelectrode configurations show a different behavior. In one type of samples, the signal stays redshifted, while in the other it blueshifts again. The effect can be explained by different hole capture processes in both types of samples.
Local Strain Effects in Near-Field Spectra of Single Semiconductor Quantum Dots.
Authors: Mintairov A. M. , Blagnov P. A. , Kovalenkov O. V. , Li C. , Merz J. L. , Oktyabrsky S. , Sun K. , Tokranov V. , Vlasov A. S. , Vinokurov D. A. 
Published: April 2011

ABSTRACTExperimental and theoretical investigations of high-energy shifts of single InAs, InGaAs, InAlAs and InP quantum dot (QD) emission lines induced by contact pressure exerted by a near-field optical fiber tip are reported. “Pressure” coefficients of 0.65–3.5 meV/nm have been measured for ground state emission lines in agreement with numerical calculations. We show that the observed increase of the tip-induced energy shift with increasing aperture diameter is caused by a decrease of the uniaxial strain component. We also report the effect of emission instability of single QD emission intensity under tip-induced pressure.
Mechanisms of Visible Photoluminescence from Size-Controlled Silicon Nanoparticles
Authors: Makino Toshiharu , Suzuki Nobuyasu , Yamada Yuka , Yoshida Takehito , Umezu Ikurou , Sugimura Akira 
Published: April 2011

ABSTRACTWe have observed visible photoluminescence (PL) spectra (peak energy: 3.1 eV) of size-controlled silicon (Si) nanoparticles annealed in oxygen gas. The PL peak energy did not depend on the temperature, and the PL lifetime was relatively fast (on the order of nanoseconds). It was inferred that the visible PL was attributed to localized states in the oxidized surfaces of size-controlled Si nanoparticles. We also observed the PL excitation spectra and studied the excitation process. In order to elucidate mechanisms of the visible PL, excitation and recombination processes are discussed.
Synthesis and size control of Si nanocrystals by SiO/SiO2 superlattices and Er doping
Authors: Heitmann J. , Kovalev D. , Schmidt M. , Yi L.X. , Scholz R. , Eichhorn F. , Zacharias M. 
Published: April 2011

ABSTRACTThe synthesis of nc-Si by reactive evaporation of SiO and subsequent thermal induced phase separation is reported. The size control of nc-Si is realized by evaporation of SiO/SiO2 superlattices. By this method an independent control of crystal size and density is possible. The phase separation of SiO into SiO2 and nc-Si in the limit of ultrathin layers is investigated. Different steps of this phase separation are characterized by photoluminescence, infrared absorption and transmission electron microscopy measurements. The strong room temperature luminescence of nc-Si shows a strong blueshift of the photoluminescence signal from 850 to 750 nm with decreasing crystal size. Several size dependent properties of this luminescence signal, like decreasing radiative lifetime and increasing no-phonon transition properties with decreasing crystal size are in good agreement with the quantum confinement model. Er doping of the nc-Si shows an enhancement of the Er luminescence at 1.54 μm by a factor of 5000 compared to doped SiO2 layers. The decreasing transfer time for the nc-Si to Er transition with decreasing crystal size can be understood as additional proof of increasing recombination probability within the nc-Si for decreasing crystal size.
Transport Properties and Observation of Semimetal-Semiconductor Transition in Bi-based Nanowires
Authors: Lin Yu-Ming , Cronin Stephen B. , Rabin Oded , Ying Jackie Y. , Dresselhaus Mildred S. 
Published: April 2011

ABSTRACTTemperature-dependent resistance measurements of Bi-related nanowire arrays with different wire diameters and Sb concentrations are performed. The variation in the measured R(T) curves of these nanowires is closely related to the unique semimetal-semiconductor transition in Bi, and the results are explained by theoretical simulations. It is found that the special feature of the maximum in the resistance ratio R(10 K)/R(100 K) can be employed to experimentally identify the conditions for the semimetal-semiconductor transition.
Thermoelectric Nanowires By Template Synthesis: Fabrication, Contacts and Properties
Authors: Rabin Oded , Lin Yu-Ming , Cronin Stephen B. , Chen Gang , Dresselhaus Mildred S. 
Published: April 2011

ABSTRACTUsing the technique we have developed to grow porous anodic alumina (PAA) templates on the surface of silicon wafers, we have fabricated arrays of nanowires of thermoelectric materials. By this method we can control both (1) the in-plane geometry by the design of the template and the substrate, and (2) the out-of-plane dimension by control over the electrochemical nanowire growth process. We use several straightforward methods to make electrical contacts to the nanowires. Our transport studies show that both the structure of the nanowire and the contact region have a strong influence on the observed properties of the arrays.
Synthesis by Self-Assembly of Iron-Cobalt Nanoalloys
Authors: Zubris Melissa A. , Tannenbaum Rina 
Published: April 2011

ABSTRACTIn this paper we are proposing the synthesis of iron and cobalt nanoalloys via the codecomposition of iron and cobalt carbonyl precursors in the presence of polystyrene as the surface stabilizing agent. In order to form iron-cobalt nanoalloys with no preferential aggregation of metal atoms resulting in phase segregation, the decomposition kinetics of the iron pentacarbonyl and dicobalt octacarbonyl precursors had to be firmly established. The kinetics of cobalt cluster formation has been thoroughly investigated, but data for iron pentacarbonyl decomposition is relatively scarce. To fully understand the formation of the iron nanoclusters, a kinetic study was performed by varying carbonyl concentrations and reaction media in order to establish reaction order and rate constants. Our results suggest this decomposition to be a higher order process (not first order as previously assumed), with a complicated intermediate mechanism, which has been postulated and experimentally verified. By using this kinetic data, we will be able to predict the necessary conditions for the creation of new in-situ iron-cobalt nanoalloys using carbonyl precursors.
Thermally Evaporated AgGaTe2 Thin Films For Low-Cost p-AgGaTe2/n-Si Heterojunction Solar Cells
Authors: Mandal Krishna C. , Smirnov Anton , Roy Utpal N. , Burger Arnold 
Published: April 2011

ABSTRACTHigh quality polycrystalline AgGaTe2 (AGT) thin films were deposited on H-terminated n-Si substrates by controlled thermal evaporation method at various substrate temperatures (300–500 K). X-ray diffraction (XRD) studies showed that all films were of chalcopyrite structure and while the films were deposited at 300 K had random grain orientation, the films deposited at higher substrate temperature (500 K) showed preferred (112) orientation. The composition of the films was thoroughly analyzed by energy dispersive x-ray analysis (EDAX) and by x-ray photoelectron spectroscopy (XPS) with and without argon ion etching. The ultraviolet-visible (UV-Vis) spectra showed the optical bandgap of 1.16 eV, with sharper band edge for the films deposited at higher temperature. The films were p-type and the resistivities of the as deposited at 300 and 500 K were 2.8 × 104 and 1.2 × 103 Ω. cm respectively. p-AgGaTe2/n-Si heterojunction solar cells, having an active area of 0.12 cm2 and without any antireflection coating, were fabricated. It was observed that the films deposited at 500 K produced junctions with improved photovoltaic properties. Under solar simulator AM1 illumination, the improved junctions exhibited an efficiency of 4.8% whereas the films deposited at 300 K showed an efficiency of 2.1%.
The Energy Band Structures of Cd1-xZnx Te Polycrystalline Thin films and their Applications for Photovoltaic Devices
Authors: Jiagui Zheng , Lianghuan Feng , Ye Shao , Yaping Cai , Jingquan Zhang , Wei Cai , Liii Wu , Daoiin Cai , Wenjian Len , Jumu Zhu 
Published: April 2011

ABSTRACTIn the paper, Cd1-xZnxTe polycrystalline films have been prepared by co-evaporation, which can control the zinc content, using CdTe and ZnTe as the evaporation sources. The cubic phase in these films as-deposited and annealed has been demonstrated by XRD. The XRD peaks of Cd1-xZnxTe films are always between the corresponding peaks of CdTe and ZnTe. According to Vegard Formula, x values of Cd1-xZnxTe films have been confirmed from XRD data, which shows that both the calculated and experimental x values are almost identical. The optical transmission of Cd1-xZnxTe films has been measured, and the optical energy gaps have been calculated from the transmission. The band gaps vary in a quadratic way with x values, and increase with annealing temperatures. When application of Cd1-xZnxTe film as a buffer of around 80nm thick in CdS/CdTe solar cells, the structure of the cells becomes CdS/CdTe / Cd1-xZnxTe / ZnTe:Cu and their average conversion efficiency is improved by 40% where x is in the range of 0.55 to 0.65. The mentioned above results are discussed.
Effect of pressure-enhanced single step annealing on the silicon photoluminescence
Authors: Binetti S. , Le Donne A. , Emtsev V.V. , Emtsev V.V , Pizzini S. 
Published: April 2011

ABSTRACTThe effect of single-step annealing under GPa hydrostatic pressures on the photoluminescence of Cz silicon samples has been investigated at 450, 650 and 1000°C. It has been demonstrated that the effect of applied pressure begins to be detectable at 650°C and significant at 1000°C, where not only the effect of the applied pressure but also that of the dopants was clearly evidenced. In the first case the presence of a gap level associated to self-interstitial clusters could be argued, while in the second case both the oxide segregation and the dislocation formation was shown to be enhanced by the pressure and selectively addressed to the type of doping, respectively.
Study of the Low Field Microwave Response in Yttrium Aluminates Dilutely Doped with Manganese
Authors: Rakhimov Rakhim R. , Jones David E. , Loutts George B. 
Published: April 2011

ABSTRACTMicrowave response near zero magnetic field was observed in YAlO3 and CaYAlO4 crystals dilutely doped with Mn in concentration ranging from 0.05 to 2 atomic %. The response is due to non-resonant microwave absorption, which co-exists with normal electron paramagnetic resonance (EPR) absorption due to different paramagnetic valence states of manganese. Mn2+ and Mn4+ charge states were identified in Mn-doped YAlO3, and Mn2+, Mn4+ and Mn5+ in Mn-doped CaYAlO4. The low field response has the opposite phase with respect to the paramagnetic absorption. This shows that Mn-doped YAlO3 and CaYAlO4 exhibit magnetically induced microwave absorption, which has a minimum at zero magnetic field and increases with the applied magnetic field. This effect is similar to microwave magneto-resistance effects observed in manganite perovskites, where spin-dependent electron tunneling occurs between ferromagnetically coupled manganese ions in different valence states. We show, however, that in the present case of diluted paramagnetic systems, magneto-induced microwave losses are due to intramolecular spin-dependent tunneling, where central paramagnetic ion does not change its charge state and spin-dependent charge migration occurs in the first coordination sphere of paramagnetic ion. Evidences are presented that this ion is Mn2+ exhibiting the highest electron spin S = 5/2.
Metal/Self-Assembled Monolayer/Metal Junctions for Magnetoelectronic Applications.
Authors: Ovchenkov Y. A. , Zhang Chunjuan , Redepenning J. , Doudin B. 
Published: April 2011

ABSTRACTMetal/organic self-assembled monolayer/metal junctions were investigated for junction areas 10-2 to 102 μm2. Several types and thickness of monolayers are investigated, and magnetic electrodes were made. Electroless deposition was used to make the top metal without disrupting the organic film. This deposition is activated with Pd clusters obtained by evaporation or by chemical reduction of a Pd-based catalyst. This method allows us to obtain a high yield of junctions that are not electrically shorted and are mechanically and electrically stable over a wide temperature range. Low-temperatures investigations reveal strong non-linearity in the IV curves and an increase of resistance with decreasing temperature. Zero bias anomalies observed at low temperatures are attributed to a Coulomb blockade associated with the Pd clusters.
Fabrication of MISFET exhibiting normally-off characteristics using a single-crystalline InGaO3(ZnO)5 thin film
Authors: Nomura K. , Ohta H. , Ueda K. , Kamiya T. , Hirano M. , Hosono H. 
Published: April 2011

ABSTRACTTransparent metal-insulator-semiconductor field-effect transistors (MISFETs) were fabricated using a single-crystalline thin film of an n-type transparent oxide semiconductor, a homologous compound InGaO3(ZnO)5, grown by a reactive solid phase epitaxy method. The transparent MISFET exhibited good performances with “normally-off characteristics”, “an on/off current ratio as large as 105” and “insensitivity to visible light”. Field-effect mobility was about 2 cm2(Vs)-1, which is larger than those reported previously for MISFETs fabricated in transparent oxide semiconductors. These improved performance is thought to result from the low defect density and intrinsic-level carrier concentration of the single-crystalline InGaO3(ZnO)5 film.
Evaporative Deposition of Aluminum Single Crystals
Authors: Jankowski Alan , Vallier Bob , Bliss Ann , Hayes Jeffrey 
Published: April 2011

ABSTRACTThe classic zone model for growth of evaporated deposits serves a starting point for selecting the process conditions to produce dense crystalline coatings. The columnar structure intrinsic to vapor deposits evolves from the nano-to-millimeter scale as the substrate temperature increases to the melting point. In this paper, the deposition conditions are reviewed for the evolution of a single crystal structure in metal coatings. Experimental results are presented for the electron-beam deposition of aluminum coatings up to 100 μm in thickness. The deposition of a single crystal occurs when the coating temperature exceeds 530 °C, i.e. 85% of the absolute melt point.
Metal-Oxide Interfacial Evolution in Thermally Grown Oxide Films
Authors: Mencer D. E. , Hossain M. A. , Kesmez M. , Naugle D. G. , Cocke D. L. 
Published: April 2011

ABSTRACTThe metal-oxide interface is a crucial zone in the fundamental understanding of oxide growth and growth instabilities. However, obtaining fundamental information on this buried interface has proven extremely difficult using modern surface and interfacial characterization methods. Using copper oxide growth over copper metal, examined between RT and 250°C, as a model system, we have delineated the fundamental physical chemical processes that determine the oxide growth and instabilities at the metal-oxide interface. Application of controlled thermal growth studies in combination with linear sweep voltammetry (LSV) has allowed experimental access to the metal-oxide interface with surprising characterization capabilities. The methodologies involved and the physical chemical phenomena will be discussed in context of the application of modern surface characterization methods including pulsed field desorption mass spectrometry, XPS combined with depth profiling and angular resolved methods. The evolution and alteration of the precursor oxide that develops at low temperatures <75°C will be explained on the basis of previously observed metal oxide interfacial phenomena involving coupled bulk and surface reactions. The nature of the interfacial zone will be discussed with electron transfer and oxygen absorption models that are applicable to oxide growth and instabilities in general.
Spontaneous Oscillations During The Electrodeposition of Gold Thin Films
Authors: Ravaine Serge , Saliba Raphaël , Mingotaud Christophe , Argoul Françoise 
Published: April 2011

ABSTRACTThe galvanostatic electrodeposition of two-dimensional (2D) gold films along the surface of aqueous hydrogen tetrachloroaurate solutions coated by a positively charged dimethyldioctadecylammonium (DODA) monolayer is reported. When a constant current is applied to the working electrode, a transition between two-dimensional (2D) growth and three-dimensional (3D) thickening of the deposits is observed. This event occurs when the current density is sufficiently small to allow the 3D process to consume all the injected electrical charges. The application of a current ramp with a rate such as the current density remains during the whole growth close to the limiting value separating the two growth regimes induces the appearance of spontaneous oscillations between the regimes of 2D and 3D growth. Deposits with a well-defined terraced structure are then obtained.
An MBE and Modeling Study of Pulsed Growth on Ge(001)
Authors: Gallivan M. A. , Atwater H. A. 
Published: April 2011

ABSTRACTGe molecular beam epitaxy (MBE) and kinetic Monte Carlo (KMC) simulations are used to study time-varying processing parameters and their effect on surface morphology. We focus here on Ge growth on highly-oriented Ge(001) substrates with reflection high-energy electron diffraction (RHEED) as a real-time sensor. KMC simulations are used as the physical model, and physical parameters are determined from growth under pulsed flux. A reduced version of the simulations is generated, and temperature trajectories are computed that minimize surface roughness subject to experimental constraints.
Surfactant Mediated Epitaxial Growth of Co on Au(111) Surface
Authors: Kamiko Masao , Oh Sang-Mun , Chihaya Hiroaki , Mizuno Hiroyuki , Xu Junhua , Yu Lihua , Kojima Isao , Yamamoto Ryoichi 
Published: April 2011

ABSTRACTWe have chosen Bi as the surfactant atom in the heteroepitaxial growth of Co on Au(111). It was found that Bi induces layer-by-layer (LBL) growth at room temperature. With pre-deposition of 0.2 ∼ 0.8Å Bi on Au(111) prior to the evaporation of Co, more long-lasting RHEED intensity oscillations were observed and this implies that it induces the LBL growth of Co film. The result of the dependence of the growth behavior as a function of Bi layer thickness suggests that there is a suitable amount of Bi surfactant layer that induces the smoother LBL growth. A surface segregation of Bi was found at the top of surface and acts as a surfactant by promoting the interlayer transport.
Adsorption of water molecules on the surface of photo-catalyst: a first principles theoretical comparison between InVO4 and rutile TiO2
Authors: Oshikiri M. , Boero M. , Ye J. 
Published: April 2011

ABSTRACTThe adsorption process of water molecules on the surface of InVO4 has been investigated via first principles molecular dynamics simulations and compared with that of the well-known rutile TiO2. We have found that the surface of InVO4 shows a remarked chemical reactivity whenever comes in contact with water and H2O molecules are often adsorbed dissociatively on its surface. The reaction proceeds spontaneously in a way similar to the case of TiO2 and does not require the overcoming of an activation energy barrier. The peculiar atomic connectivity of the InVO4 bulk crystal structure and the changes at the catalyst surface induced by the water adsorption are discussed and compared with the TiO2 system.