bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge Retention in Single Silicon Nanocrystal Layers
Authors: Krishnan Rishikesh , Krauss Todd D. , Fauchet Philippe M. 
Published: April 2011

ABSTRACTSilicon (Si) nanocrystals formed by controlled thermal crystallization of amorphous silicon dioxide (a-SiO2)/amorphous silicon (a-Si)/amorphous silicon dioxide (a-SiO2) layers hold considerable promise for application in non-volatile memory products and optoelectronic devices. The size of the nanocrystals is fixed by the thickness of the Si layer and strong quantum confinement is provided in the vertical (growth) direction by the insulating a-SiO2 layers. However, the extent of quantum confinement in the lateral dimensions remains to be established. Electron energy loss spectroscopy (EELS) measurements performed within a scanning transmission electron microscope (STEM) indicate that the nanocrystals are laterally isolated by approximately 2nm of a-SiO2. The confinement potential provided by this barrier is insufficient to localize carriers within a nanocrystal for prolonged durations and can permit quantum mechanical tunneling via wave function overlap between adjacent nanocrystals. Charge leakage kinetics within a sheet of Si nanocrystals was studied using electric force microscopy. Approximately 750 electrons were injected within a 100nm radius circular patch with an atomic force microscope cantilever. The entire charge dissipated from this area in 70min via lateral conduction routes. With a goal of localizing the injected charge and enhancing its retention time, the samples were subjected to relatively low temperature dry oxidation at 750°C. After 20 min of oxidation, retention times above 400 minutes were observed.
Formation of SiGe Nanoparticles by Dry and Steam Thermal Oxidation of Thin Polycrystalline Layers
Authors: Ortiz M. I. , Ballesteros C. , Rodríguez A. , Sangrador J. , Rodríguez T. , Avella M. , Martín P. , Jiménez J. 
Published: April 2011

ABSTRACTNanoparticles embedded in a dielectric medium have been formed by dry and steam thermal oxidation at specific temperatures and process times of polycrystalline Si0.7Ge0.3 layers deposited on thermally oxidized Si substrates. We present a study of the influence of the oxidation process parameters: oxidation atmosphere, temperature and time on: a) the composition of the grown oxide, b) the Ge segregation, c) the formation of nanoparticles, their composition and size, and d) the properties of the cathodoluminescence emission of the oxidized films. Oxidation in a dry O2 atmosphere results in a full Ge segregation. The formation of Ge islands embedded in an oxide matrix is demonstrated. Ge segregation is slower in steam thermal oxidation than in dry O2. In this case Ge-rich SiGe particles are formed. In both processes, an important increase in the cathodoluminescence emission associated with the presence of Ge rich nanoparticles is obtained.
Effect of Surface Treatments in Nanocrystalline Silicon
Authors: Mandal N. P. , Dey S. , Agarwal S. C. 
Published: April 2011

ABSTRACTExposure to ammonia (NH3) increases the dark current (DC) in porous silicon (PS), but evaporated selenium (Se) deposited on PS decreases DC. Photoluminescence (PL) measurement shows that there are two types of centers. PL in one region of PS (Peak ∼ 800nm) initially increases with the NH3 exposure and then decreases. But the PL from another region of PS has a peak at ∼ 780nm and it decreases continuously with the NH3 exposure. Dipping PS in water and drying in air shifts the PL peak at 800 nm to 744 nm. Atomic Force Microscopy (AFM) shows that the as prepared sample has wires of diameters 2.4nm, 3.4nm, 4.6nm and bigger. However, in the AFM images of the water treated sample the wires of diameters 3.4nm and 4.6nm are absent. The PL results are explained using the AFM data and the John-Singh model of quantum confinement.
Comparative Study Of The Growth Curves Of B. subtilis, K. pneumoniae, C. xerosis And E. coli Bacteria In Medium Containing Nanometric Silicon Particles
Authors: Pérez Lilyanna , Flores Marjorie , Avalos J. , San Miguel L. , Resto O. , Fonseca L. 
Published: April 2011

ABSTRACTIn this research nanometric particles from luminescent (625nm) porous silicon film were synthesized. This particles were later inoculated in bacterial strains of B. subtilis (BSi) and K. pneumoniae (KSi). A comparison of the behavior of their growth curve and the ones reported for C. xerosis (XSi) and E. coli (ESi) in presence of silicon nanoparticles is presented. The growth curve of BSi, as well as the KSi, present changes compared to their standard curves. The BSi growth curve grows below the standard curve after the fifth hour, while in the KSi this happens after the eighth hour. Based on our preliminary findings we can speculate that at this point in time a critical population is present, and this may give rise to the possible incorporation of the silicon particles by the bacteria, or a possible pleomorphism inhibits reproduction. The stationary region, in both cases, takes place sooner than in the standard curve. No significant oscillations are observed in any case, which differs form the XSi curve, were oscillations of intervals of almost 1 hour were reported. In addition, these curves have a different behavior when compared to the ESi growth curve, in which no significant differences between the standard and the particle containing sample were reported.
Evidence of Ti-related Inclusions in an Al Alloy Interconnecting Layer for Nanometer 256MBit DRAM Semiconductor Devices Characterized by TEM, STEM, EELS Elemental Mapping, and XEDS Linescan
Authors: Zhao Wei , Graca Steve 
Published: April 2011

ABSTRACTWith the introduction of high aspect ratio and steep geometries in deep-subquarter-micron dynamic random access memory (DRAM) device, it becomes more and more critical to understand the formation of undesired intermetallic Ti-Al phases in Al-metallization and thus better-control the profile of interconnectors. In this article, Ti-related inclusions in Metal 1 (M1) interconnecting layer (an AlCu-0.5% alloy) originated from the bottom Ti liner were characterized with an Analytical TEM. Samples were cleaved from nanometer 256Mbit dynamic random access memory DRAM devices. The TEM employed is a JEOL 2010F with a field emission gun (FEG) and running at 200KV acceleration voltage. Correlations among transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) elemental mapping, and x-ray energy dispersive spectroscopy (XEDS) elemental linescan were established. The results here not only provide important feedbacks to semiconductor product integration and optimization, but also demonstrate the full-functionality of the start-of-the-art analytical TEM in investigations of nanometer semiconductor devices.
Moisture effects of crack initiation in nanocrystalline silicon: a hybrid density-functional/molecular-dynamics study
Authors: Ogata Shuji , Belkada Rachid , Shimojo Fuyuki , Nakano Aiichiro 
Published: April 2011

ABSTRACTA hybrid quantum-mechanical/molecular-dynamics simulation is performed for a cracked-Si model under tension with multiple H2O molecules around the crack-front, to investigate possible effects of the environmental molecules on fracture initiation in Si. Electronic structures near the crack-front are calculated quantum-mechanically on the basis of the density-functional theory. The quantum-mechanical atoms are embedded in a system of classical atoms. The hybrid simulation results show significant effects of stress intensity factor on the reaction processed of the H2O molecules at the crack front.
Sol-gel synthesis and characterization of CuO–based nanosystems
Authors: Armelao Lidia , Barreca Davide , Bertapelle Manuel , Bottaro Gregorio , Sada Cinzia , Tondello Eugenio 
Published: April 2011

ABSTRACTThis paper is focused on the sol-gel synthesis and characterization of CuO-based nanosystems both in the form of supported films and as guest nanoclusters embedded in a silica matrix. In both cases copper acetate (Cu(CH3COO)2· H2O) was used as Cu source and, for the CuO :SiO2nanocomposite systems, tetraethoxysilane (Si(OC2H5)4, TEOS) was adopted as silica precursor. Films were obtained by a dip-coating procedure and subsequently treated in air between 100 and 900°C. The system evolution on thermal annealing was studied by X-ray photoelectron spectroscopy (XPS), Glancing-Incidence X-ray diffraction (GIXRD) and optical absorption. Irrespective of the processing conditions, the formation oftenorite(CuO) crystallites with nanometric dimension was observed. In the nanocomposite samples, copper was homogeneously distributed in the host matrix and stable CuO nanoclusters (φ ≈ 15 nm) were obtained.
Techniques and Applications for Non-Planar Lithography
Authors: Rogers John A. 
Published: April 2011

ABSTRACTCertain classes of three dimensional nanostructures can be fabricated by contact printing patterns onto curved or non-flat surfaces. This paper reviews some of our work that demonstrates this approach by using microcontact printing to form a range of three dimensional structures with feature sizes as small as 1–2 microns and it demonstrates their use in a variety of functional devices. We also describe a nanotransfer printing technique with operational characteristics that are similar to those of microcontact printing but which enables nanometer resolution. High resolution replica molding techniques provide a method for producing copies of some of these printed structures.
Finite Element Analysis of Nanoscale Thermal Measurements of Superlattices
Authors: Foley Jason R. , Thomas Avedisian C. 
Published: April 2011

ABSTRACTA finite element analysis applicable to two- and three-dimensional heat flow in samples of arbitrary geometry and composition is presented for use in a thermal wave experiment. The finite element formulation is summarized, including the use of symmetry to simplify the problem, and the governing differential equations for the heat transport are found to be in the form of the Helmholtz equation for the specific case of a modulated heat source. Simulated data for a Nb/Si superlattice is calculated using the finite element code and is shown to agree with predictions from an analytical model, validating the approach taken.
Application of a Focused Ion Beam System to Nanolithography
Authors: Langford Richard M. , O'Reilly Shamus , McEwen Iain J. 
Published: April 2011

ABSTRACTNano-imprint lithography (NIL) and micro-contact printing (MCP) are currently receiving considerable attention as techniques that can be used for low cost nanolithography. Here the application of a focused ion beam (FIB) system for the analysis of the elastomer stamps and imprinted patterns which are used in these nanolithography techniques is discussed. It is shown that the ‘lift-out’ technique can be used to prepare cross-sections of both the elastomer poly(dimethylsiloxane) (PDMS) stamps and the imprinted poly(methylmethacrylate) (PMMA) patterns. In addition, the use of the FIB system to prepare masters such as gratings and structures with curved shapes that would be difficult to fabricate using conventional processing techniques is discussed.
Dendrimer Mediated ‘Bricks and Mortar’ Self-Assembly of Nanoparticles
Authors: Frankamp Benjamin L. , Boal Andrew K. , Rotello Vincent M. 
Published: April 2011

ABSTRACTControl of particle-particle spacing is a key determinant of optical, electronic, and magnetic properties of nanocomposite materials. We have used poly(amidoamine) (PAMAM) dendrimers to assemble carboxylic acid-functionalized mixed monolayer protected clusters (MMPCs) through acid/base chemistry between particle and polymer. IR spectroscopy and selective dendrimer staining, observed by Transmission Electron Microscopy (TEM), establish that the PAMAM dendrimers are the mortar in the assembly and act to space the MMPCs in the resulting aggregates. Small angle X-ray scattering (SAXS) was then used to establish average interparti cle distances; five generations of PAMAM dendrimer (0, 1, 2, 4, 6) were investigated and monotonic increase in interparticle spacing from 4.1 nm to 6.1 nm was observed.Initial studies involving the application of this methodology to control the magnetic properties of 3-iron oxide nanoparticles have been completed. γ-Iron oxide nanoparticles (6.5 nm in diameter) have been assembled with PAMAM dendrimers generations 2.5, 4.5, and 6.5. The resulting aggregates were characterized with SAXS and magnetization obtained on a super conducting quantum interference devise (SQUID). An observed correlation between the blocking temperature (TB) and the average interparticle spacing suggests that our methodology could be used to tailor the magnetic profile of the nanoparticles.
MBE Growth and Optical Properties of ZnSeO
Authors: Nabetani Y. , Mukawa T. , Ito Y. , Kato T. , Matsumoto T. 
Published: April 2011

ABSTRACTZnSeO alloy was successfully grown by molecular beam epitaxy on GaAs substrate using RF plasma. The crystal structure of epitaxial ZnSeO alloy was zincblende. No phase separation was observed by in-situ reflection high energy electron diffraction and X-ray diffraction measurements. O composition was estimated by lattice constant assuming Vegard's law. Photoluminescence intensity was larger than that of ZnSe. The peak energy shifted toward lower energies by increasing O composition. The band gap energy determined by photoluminescence excitation decreased with increasing O composition. The bowing parameter was obtained as high as 8.2eV. This large band gap bowing widens controllable energy range of II-VI semiconductor.
Screen Printable Doped Self-Aligned Metallization for Solar Cells
Authors: Addo Ernest A. , Shah Ismat , Opila Robert , Barnett Allen. M. , Allison Kevin , Sulima Oleg 
Published: April 2011

ABSTRACTAlloyed metal contacts to <100> and <111> p-type silicon (Si) were investigated using doped self-aligning metallization techniques [1]. The contact allows the formation of a pn-junction and provides metallization for photovoltaic applications via thick film technology [2]. A formulated screen-printable thick film was annealed above Ag/Si eutectic temperature of 830°C. The annealing process resulted in a junction depth of 0.3–1.2 μm and improved adhesion by the reduction of native oxide layer through use of a wetting agent. The technique inhibits shunts (high conductivity paths through the solar cell pn-junction caused by excessive metallization penetration). The technique also reduces the interfacial resistance due to dissimilar materials in contact – a parasitic resistance that also limit solar cell performance. The use of metallic Mg as a wetting agent additive in the thick film silver matrix was explored. Studies were carried out on screen printable thick films and the reducing effects of Mg were investigated using both air and reducing atmosphere (H2) annealing furnaces. We observed a correlation between increased alloying with reduced series resistance.
Characterization of Sputter Deposited PbTe on Si (111) for Optoelectronic Applications
Authors: Jdanov Alexey , Dashevsky Zinovi , Pelleg Joshua , Shneck Roni 
Published: April 2011

ABSTRACTIV-VI compound semiconductors are of interest due to their potential application as thermoelectric material, infrared detectors and semiconductor lasers. The use of PbTe based semiconductors is usually in the middle and far infrared region. Magnetron sputtering of PbTe thin films from a single target on Si (111) was performed under various conditions. Characterization of the films shows that PbTe films on Si (111) substrate are suitable for preparation of infrared (IR) detectors. By heat treatment novel IR detectors can be developed in the electron absorption region of 4 – 10 μm.
Far-infrared dielectric function and phonon modes of spontaneously ordered (AlxGa1-x)0.52In0.48P
Authors: Hofmann Tino , Gottschalch Volker , Schubert Mathias 
Published: April 2011

ABSTRACTWe present a far-infrared spectroscopic ellipsometry study of the phonon properties of partially CuPtB -ordered (AlxGa1-x)0.52In0.48P with x =0, 0.32, 0.7, and 1.0 and degrees of ordering η = 0 … 0.63, determined from generalized ellipsometry measurement of the near-band-gap order birefringence. An anharmonic oscillator approach is used to model the ordinary and extraordinary dielectric functions and determine the infrared-active longitudinal and transversal phonon modes of the thin film samples. Besides the isotropic GaP-, InP- and AlP-like phonon modes, we observe alloy-induced modes with low polarity for η ∼ 0. The evolution of lattice like and alloy-induced modes with increasing η is reviewed for Ga0.52In0.48P. With increasing η all phonon modes split in E- and A1 -type vibrations with polarization perpendicular and parallel to the sublattice ordering direction, respectively, and the mode frequencies shift continuously. Our observations extend recently published phonon frequencies from experiment and theory for CuPt-ordered Ga0.52In0.48P, which are compared and discussed. The phonon modes of highly ordered (AlxGa1-x)0.52In0.48P, η ∼ 0.6, are compared to the modes observed in the highly disordered quaternary solid solution. We propose the far-infrared dielectric anisotropy as a sensitive measure for sublattice ordering in multinary III-V alloys.
Electrodeposition of CU2SE thin films by Electrochemical Atomic Layer Epitaxy (EC-ALE).
Authors: Vaidyanathan Raman , Mathe Mkhulu K. , Sprinkle Patrick , Cox Steve M , Happek Uwe , Stickney John L 
Published: April 2011

ABSTRACTElectrochemical atomic-layer epitaxy (EC-ALE) is an approach to electrodepositing thin-films of compound semiconductors. It takes advantage of underpotential deposition (UPD), deposition of a surface limited amount (a monolayer or less) of an element at a potential less negative than bulk deposition, to form a thin-film of a compound--one atomic layer at a time. Ideally, the 2-D growth mode should promote epitaxial deposition.We report the formation of compound Cu2Se, at room temperature by electrochemical atomic layer epitaxy (EC-ALE). Cyclic voltammograms were used to determine the deposition potentials of each element. An automated deposition program was used to form 750 cycles of Cu2Se thin films. Electron probe microanalysis was done to determine the stoichiometry of the thin films. X-ray diffraction of the 200 cycle deposit indicated the presence of polycrystalline Cu2Se. The atomic ratio of Cu/Se in the thin films was found to be 2. Band gap of the thin films were determined by reflection absorption measurements. The band gap of the 200 cycle Cu2Se films was found to be 1.6 eV. X-ray diffraction of 350 and 750 cycle Cu2Se films, indicated the deposits consisted of Cu3Se2 and Cu2Se.
Native Point Defect Interactions in ZGP Crystals under Influence of e-Beam Irradiation.
Authors: Gribenyukov A.I. , Verozubova G.A. , Trofimov A. Yu. , Vere A.W. , Flynn C. J. 
Published: April 2011

ABSTRACTOptical absorption in the defect-related region of highly efficient non-linear ZnGeP2 crystals under e-beam irradiation and post-irradiation anneals has been investigated.Partially irreversible changes of the absorption were found in the spectral range 0.9–2.5 μm (0.5–1.3 eV) after irradiation and subsequent low-temperature anneals. Data obtained do not support the vacancy model for ZnGeP2 absorption in the 0.5–1.3 eV range.The least squares fit for the parameters of the theoretical dependence of optical absorption cross-section to the experimentally measured ZnGeP2 optical absorption coefficient spectra show that the defect-related absorption in 0.5–1.3 eV region is caused by deep donor levels with energy position E=Ev+(0.85–0.90) eV.Significant changes in the energy spectrum of the dominant optically active centers have been observed under influence of e-beam irradiation and post-irradiation anneals.Based on the optical absorption measurements obtained for as-grown, annealed and e-irradiated ZnGeP2 crystals, a model of point defect interactions has been proposed. This takes into account both the reversible interactions, such as the formation of donor-acceptor pairs, and the irreversible interactions of a quasi-chemical type.The behavior of the energy spectrum of the optically active defects is discussed in terms of the modes of interaction between the initial point defects and those generated by irradiation. The analysis performed showed that the best agreement with experimental data is reached when it is assumed that optical defect-related absorption in the 0.5–1.3 eV range related mainly to the disordering defect in the cation sublattice of ZnGeP2, namely, to atoms of Ge substituting for Zn.Defect concentration profiles created by e-irradiation in ZGP crystals of different thickness were calculated. The optimum conditions for providing a uniform defect distribution with depth in irradiated ZnGeP2 samples were determined.The optimal e-beam irradiation fluences, giving maximum ZnGeP2 enlightenment, allowed us to reduce the defect-related absorption down to a value of 0.01 cm-1 at 2 μm.
Interdiffusion in Semiconductor Quantum Dot Structures
Authors: Lever P. , Fu L. , Jagadish C. , Gal M. , Tan H.H. 
Published: April 2011

ABSTRACTThe potential profile of InGaAs quantum dots (QDs) was shown to be easily modified with annealing. We also demonstrate the use of spin-on-glass to create interdiffusion in QDs but the degree of interdiffusion was strongly dependent on the properties of the oxide. By using TiO2 significant suppression of thermal diffusion of the quantum dots could be achieved. On the other hand, very large additional blue shifts (in excess of 120 meV) could be obtained with both H and As implantation. The different nature of defects created by both ions and how they affect the interdiffusion of quantum dots were illustrated. In the dose and annealing temperature range studied, the degree of interdiffusion ultimately depends on the availability of free point defects or point defects liberated from clusters/extended defects to diffuse across the quantum dots.
Defects, Tunneling, and EPR Spectra of Single-Molecule Magnets
Authors: Park Kyungwha , Novotny M. A. , Dalal N. S. , Hill S. , Rikvold P. A. , Bhaduri S. , Christou G. , Hendrickson D. N. 
Published: April 2011

ABSTRACTWe examine theoretically electron paramagnetic resonance (EPR) lineshapes as functions of resonance frequency, energy level, and temperature for single crystals of three different kinds of single-molecule nanomagnets (SMMs): Mn12 acetate, Fe8Br, and the S = 9/2 Mn4 compound. We use a density-matrix equation and consider distributions in the uniaxial (second-order) anisotropy parameter D and the g factor, caused by possible defects in the samples. Additionally, weak intermolecular exchange and electronic dipole interactions are included in a mean-field approximation. Our calculated linewidths are in good agreement with experiments. We find that the distribution in D is common to the three examined single-molecule magnets. This could provide a basis for a proposed tunneling mechanism due to lattice defects or imperfections. We also find that weak intermolecular exchange and dipolar interactions are mainly responsible for the temperature dependence of the lineshapes for all three SMMs, and that the intermolecular exchange interaction is more significant for Mn4 than for the other two SMMs. This finding is consistent with earlier experiments and suggests the role of spin-spin relaxation processes in the mechanism of magnetization tunneling.
Origin of the Magnetic Proximity Effect
Authors: Kiwi Miguel 
Published: April 2011

ABSTRACTThe magnetic proximity effect (MPE) has attracted the attention of theorists and experimentalists for at least three decades. Lately, the relevance of the effect for the development of nanodevices has revived interest on the subject. Here we review how the field has evolved, centering our attention on metal-metal and metal-insulator systems. We describe, and critically compare, the different theoretical approaches that have been put forward, as well as their limitations. An evaluation of the relationship between existing theories and available experimental results is also attempted.