bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Analytical Compact Direct-Current and Capacitance Model for AlGaN/GaN High Electron Mobility Transistors
Authors: Li Miao , Cheng Xiaoxu , Wang Yan 
Published: April 2011

ABSTRACTWe develop an analytical model for the Direct-Current (DC) and capacitance-voltage (CV) characteristics of AlGaN/GaN High Electron Mobility Transistors (HEMTs), providing accurate predictions of the transconductance and the gate capacitance in both linear and velocity saturation regions. The models provide an accurate and smooth connection in the area near the knee point for the DC characteristics, which is attributed to precise descriptions of the channel charge. An accurate model for the low-field mobility of the two dimensional electron gases (2DEG) has been developed, considering the nonmonotonic dependence of the carrier velocity on the electric field perpendicular to the channel for the first time. The calculated transconductance and output conductance are proved accurate and to have high order continuity, especially in large voltage biases, which is hard for some other analytical or numeral models. The gate capacitance has been obtained analytically and verified by experimental data. The slight decrease in the measured gate-to-source capacitance over the velocity saturation region which indicates the results of neutralization of donors and the contribution of the free electron in the AlGaN layer has been modeled accurately and smoothly for the first time. The predicted cut-off frequency is in excellent agreements with measured data over the full range of applied biases. The models are implemented into the HSPICE simulator for the DC, AC and transient simulations, with good speed and convergence characteristics.
Simulation of Capacitance-Voltage characteristics of Ultra-thin Metal-Oxide-Semiconductor Structures with Embedded Nanocrystals
Authors: Rahman Mosur , Lojek Bo , Kalkur Thottam 
Published: April 2011

AbstractThis paper presents an approach to model quantum mechanical effects in solid-state devices such as Metal Oxide Semiconductor (MOS) capacitor with and without nanocrystal in the oxide at the device simulation level. This quantum-mechanical model is developed to understand finite inversion layer width and threshold voltage shift. It allows a consistent determination of the physical oxide thickness based on an agreement between the measured and modeled C-V curves. However, as for thinner oxides finite inversion layer width effects become more severe, quantum-mechanical model predicts higher threshold voltage than the classical model. The inversion-layer charge density and MOS capacitance in multidimensional MOS structures are simulated with various substrate doping profiles and gate bias voltages. The effectiveness of the QM correct method for modeling quantum effects in ultrathin oxide MOS structures is also investigated. The CV characteristic is used as a tool to compare results of the QM correction with that of the Schrödinger–Poisson (SP) solution and Classical solution The variation of (different parameters) for various doping profiles at different gate voltages is investigated.
Stability of Larger Ferromagnetic Chain-of-sphere Nanostructure Comprising Magnetic Vortices
Authors: Barpanda Prabeer 
Published: April 2011

AbstractChain-of-sphere (CoS) nanostructure containing Permalloy (Fe20Ni80) nanospheres of uniform size (d=50 nm) has been studied using micromagnetic simulation. These large-size Permalloy nanospheres support magnetic vortex structure upon relaxation. The presence of magnetic vortices in CoS architecture affects its magnetic properties significantly. Micromagnetic behaviour of Permalloy CoS system was studied focusing on the magnetization reversal process. The presence of magnetic vortices triggers a vortex creation and annihilation mechanism (VCA) involving the formation and breaking of an inversion symmetry (IS) feature. This VCA mechanism has been studied using 3D micromagnetic simulation and results of coercivity and vortex parameters are presented.
New Physical and Chemical Treatments to Improve the Quantum Efficiency in Polymer Solar Cells
Authors: Yoshikawa Osamu , Sonobe Taro , Sagawa Takashi , Yoshikawa Susumu 
Published: April 2011

AbstractThe performance of the devices of bulk heterojunction polymer-based solar cells were investigated by using poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as light absorption (viz. active) layer, with TiOx as interlayer as follows: ITO/PEDOT:PSS/P3HT-PCBM/TiOx/Al [1] through the treatment of microwave irradiation (single mode of 2.45 GHz, 800 W for 1, 2.5, or 5 min). Such treatments enabled to increase the short-circuit current density Jsc (from 4.53 mA cm−2 to 7.27 mA cm−2) and fill factor FF (from 0.41 to 0.66) of the cell, though the open circuit voltage Voc was decreased (from 0.61 V to 0.57 V) along the irradiation. Absorption spectra of P3HT-PCBM blended film before and after the microwave treatment were observed. Shoulders at 550 nm and 600 nm appeared after the irradiation. This result implies that the microcrystallization of P3HT was slightly promoted through the microwave treatment.
Octadecyltriethoxysilane Surface Modification of Zinc Oxide
Authors: Allen Cary , Baker Darick J. , Furtak Thomas E. , Collins Reuben T. , White Matthew S. , Gillaspie Dane T. , Olson Dana C. , Ginley David S. 
Published: April 2011

AbstractZinc Oxide (ZnO) is actively investigated for hybrid organic inorganic device applications. The interface greatly influences the electronic properties of these devices. Molecular surface modification of ZnO is being investigated for its potential to control the alignment of energy levels, charge transfer, as well as, interfacial chemical characteristics that influence device fabrication. In this study, octadecyltriethoxysilane (OTES) treatments of thin film ZnO produced by sol-gel decomposition were explored. The ZnO films were hydroxylated and then modified using OTES in solution. The condensation reaction of the OTES at the surface was promoted by the addition of a protoamine catalyst. Contact angle and infrared spectroscopy studies confirmed the surface modification and indicated that the coverage of the OTES was submonolayer. The modified ZnO films were reproducible and stable for long periods. The effects of the modification on subsequently spin-cast poly[3-hexylthiophene](P3HT) and on hybrid ZnO/P3HT organic solar cell performance are discussed.
Diethynyl Aryl Derivatives for P-Channel and N-Channel Organic Field-Effect Transistors
Authors: Yasuda Takeshi , Kashiwagi Kimiaki , Morizawa Yoshitomi , Tsutsui Tetsuo 
Published: April 2011

AbstractOrganic field-effect transistors (OFETs) consisted of vacuum-evaporated diethynyl aryl derivatives were prepared and the device characteristics were evaluated. The fabricated OFETs showed typical p-type characteristics for diethynyl naphthalene derivative with two end naphthyl groups. By optimizing the fabrication process, the device exhibited a high field-effect hole mobility up to 0.12 cm2V−1s−1 and a high on/off current ratio of 3.3×105. On the other hand, OFETs showed typical n-type characteristics for diethynyl aryl derivative with two end heptafluoronaphthyl groups. We have observed clear changes from p-channel to n-channel conductions in OFETs by chemically modifying diethynyl aryl derivatives.
Anisotropic Charge Transport in Organic Single Crystals Based on Dipolar Molecules
Authors: Fraboni Beatrice , Di Pietro Riccardo , Castaldini Antonio , Cavallini Anna , Fraleoni Alessandro , Setti Leonardo , Mencarelli Ivan , Femoni Cristina 
Published: April 2011

AbstractWe studied the anisotropic charge transport properties of solution-grown organic single crystals based on a dipolar molecule 4HCB (4-hydroxy-cyanobenzene) by electrical transport measurements, current-voltage and space charge limited current (SCLC), and by X-ray diffraction analyses.Optical excitation differently affects the flow of charge carriers along the two main planar crystal axis, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice. The anisotropy of transport along the three crystallographic directions has been assessed by electrical characterization and correlated to the crystal molecular packing as determined by X-ray analyses.
Synthesis of Fullerene by Spark Plasma Sintering and Thermomechanical Transformation of Fullerene Into Diamond on Fe-C Composites
Authors: Robles-Hernández Francisco C. , Calderon H. A. 
Published: April 2011

ABSTRACTIn this work, results are presented regarding the characterization of nanostructured Fe matrix composites reinforced with fullerene. The fullerene is a mix of 15 wt.%C60, 5 wt.%C70 and 80 wt.% soot that is the product of the primary synthesis of C60. The composite has been produced by means of mechanical alloying and sintered by Spark Plasma Sintering (SPS). The characterization methods include XRD, SEM and TEM. The C60 and C70 withstand mechanical alloying, SPS, and thermomechanical processing and act as a control agent during mechanical alloying. The results show that the mechanically alloyed and SPS product is a nanostructured composite. A larger amount of C60 is found in the sintered composite than in the original fullerene mix, which is attributed to an in-situ synthesis of C60 during the SPS process. The synthesis of C60 is presumably assisted by the catalytic nature of Fe and the electric field generated during the SPS process. In order to study the effect of high temperature, high strain, high heating and cooling rates on C60, the composite is subjected to a thermomechanical processing; demonstrating that some of the C60 resists the above described environment and some of it partially transforms into diamond.
Atomic-Resolution Chemical Analysis at 100 Kv in the Scanning Transmission Electron Microscope
Authors: Browning N. D. , Chisholm M. F. , Pennycook S. J. 
Published: April 2011

ABSTRACTIn a 100 kV VG HB501 UX dedicated scanning transmission electron microscope, the 2.2 Å probe size allows the atomic structure to be observed with compositional sensitivity in the Z-contrast image. As this image requires only the high-angle scattering, it can be used to position the probe for simultaneous electron energy loss spectroscopy. Energy loss signals in the core loss region of the spectrum (>300 eV) are sufficiently localized that the spatial resolution is limited only by the probe. The electronic structure of the material at the interface can thus be determined on the same scale as the changes in composition, and atomic structure can be observed in the image, allowing the structure and chemical bonding at interfaces and boundaries to be characterized at the atomic level.
Nanoanalytical Characterization of Granular Ag-Fe Films with Giant Magnetoresistance
Authors: Liu J. , Li Z. G. , Wan H. , Tsoukatos A. , Hadjipanayis G. C. 
Published: April 2011

ABSTRACTDedicated scanning transmission electron microscopy and associated techniques were used to extract microstructural and compositional information about granular Ag-Fe magnetic films produced by sputtering. Nanometer-resolution compositional analysis by energy dispersive X-ray spectroscopy (EDS), showed that Ag-Fe granular films consist of two separate phases. It has been found that nanometer size Fe particles are separated by small as well as large Ag particles. Nanodiffraction patterns showed that a large proportion of small Ag particles have an icosahedral shape and that the Fe particles are highly disordered. The nanostructure of the Ag-Fe system and its relation to the giant magnetoresistance of granular films are discussed.
Scanning Tunneling Microscopy (Stm) and Scanning Force Microscopy (Sfm) of Liquid Crystals and Polymers
Authors: Jandt K. D. , Mcmaster T. J. , Mcdonnell D. G. , Blackmore J. M. , Miles M. J. 
Published: April 2011

ABSTRACTRecent progress in the field of liquid crystal materials and oriented polymers studied by nearfield scanned probe microscopies (SPM) is presented here. The investigations were focused on scanning tunneling microscopy (STM) results of antiferroelectric liquid crystalline molecules observed at different elevated temperatures corresponding to different bulk mesophases of the material, and on surface morphological studies of a liquid crystalline polymer by scanning force microscopy (SFM). In the field of oriented thermoplastic polymers, SFM images of the morphology and molecular packing in the outermost surface of poly(butene-1) films are presented.
Surface Morphology of Diamond Thin Films Using Photoinduced Scanning Tunneling Microscopy
Authors: Carroll D.L. , Mercer T. , Liang Y. , Dinardo N.J. , Bonnell D. A. 
Published: April 2011

ABSTRACTPhoto-induced conduction in thin insulating films of diamond was used to obtain STM images indicative of film morphology. UV light was used to generate carriers in the conduction band of diamond films grown on Si (111). Tunneling currents could only be established when the tunnel junction was illuminated. Without the light, no current was measured even with the tip in contact with the surface. Two types of films were studied. A CVD grown diamond film with nitrogen impurities and a diamond-like film grown by laser ablation of graphite. Topological detail was compared to that obtained with an AFM. The correspondence between AFM and photoinduced STM images suggests that the STM images are indicative of film morphology.
Imaging The Atomic-Scale Structure of Molybdenum and Vanadium Oxides by Scanning Tunneling Microscopy
Authors: Rohrer Gregory S. , Lu Weier , Smith Richard L. 
Published: April 2011

ABSTRACTSingle crystals of Na0.003V2O5 and Mo18O52 were grown by chemical vapor transport and cleaved surfaces were imaged in ultrahigh vacuum using scanning tunneling microscopy (STM). Because the Mo18O52 (100) and Na0.003V2O5 (010) surfaces of these layered materials have a bulk terminated structure, the atomic-scale contrast in constant current images can be directly compared to components of the bulk structure. Among the structural features identified in the STM images are the surface/crystallographic shear plane intersections, the different MoOx coordination polyhedra on the Mo18O52 (100) surface, and the VO5 square pyramids that make up the Na0.003V2O5 (010) surface. In each of these cases, it was found that the atoms closest to the tip dominate the image contrast.
Characterization of InP/GaInAs Nanometer Sized Columns Produced by Aerosol Deposition and Plasma Etching
Authors: Maximov I. , Deppert K. , Montelius L. , Samuelson L. , Gray S. , Johansson M. , Hansson H.-C. , Wiedensohler A. 
Published: April 2011

ABSTRACTWe present a technique for the fabrication of InP nano-columns and GaInAs/InP quantum-dots based on the use of sintered aerosol Ag particles as a mask in an electron cyclotron resonance etching process. The sintered particles have much more regular shapes than the unsintered ones used in previous studies and are more resistant to the etching environment, which results in the formation of more regular and reproducible structures. For example, we have been able to produce columns 100 nm in height which have an average diameter of 24 nm and a density of 109 cm−2.We have investigated the shape of the etched columns as a function of the Ag particles’ size, and characterized their electrical and optical properties using a combination of scanning electron microscopy, scanning tunneling microscopy, atomic force microscopy, and photoluminescence.
Incoherent Imaging by Z-Contrast Stem: Towards 1Å Resolution
Authors: Pennycook S. J. , Jesson D. E. , Mcgibbon A. J. 
Published: April 2011

ABSTRACTBy averaging phase correlations between scattered electrons a high angle detector in the scanning transmission electron microscope (STEM) can provide an incoherent, Z-contrast image at atomic resolution. Phase coherence is effectively destroyed through a combination of detector geometry (transverse incoherence) and phonon scattering (longitudinal incoherence). Besides having a higher intrinsic resolution, incoherent imaging offers the possibility of robust reconstruction to higher resolutions, provided that some lower frequency information is present in the image. This should have value for complex materials and regions of complex atomic arrangements such as grain boundaries. Direct resolution of the GaAs sublattice with a 300kV is demonstrated.
Epitaxial Growth of Two-Dimensional Dichalcogenides and Modification of Their Surfaces with Scanning Probe Microscopes
Authors: Parkinson Bruce A. 
Published: April 2011

ABSTRACTMethods for epitaxial growth of two dimensional materials are described. The lack of interlayer bonding in these materials allows for epitaxial growth with large lattice mismatches. Growth of MoSe2 on MoS2 (a 5% mismatch) or on SnS2 (10% mismatch) can be demonstrated. Scanning tunneling microscopy (STM) revealed remarkable structures in the epilayer as a result of the large mismatches. A technique using the STM or atomic force microscope (AFM) to selectively remove single molecular layers from the surface of layered materials is also described. The combination of these two technologies may result in the ability to produce nanoscale devices exhibiting quantum size effects.
Comparison between SiO2 Films and Nitridated Oxides in N2O Ambient in Terms of Bulk/Interface Trapping Properties
Authors: Papadas Constantin , Mortini Patrick 
Published: April 2011

ABSTRACTThe necessity of employing nitridation process in advanced technologies will be underlined. The different technological alternatives for preparing oxinitride layers will be traced back, followed by a review of the methods currently available for assessing the degradation features of the Si/SiO2 system. Furthermore, comparison between pure SiO2 layers and nitridated films in N2O ambient will be conducted in terms of bulk/interface trapping properties and the obtained physical degradation data will be correlated with classical reliability results. Large emphasis will be given on the trapping properties of tunnel oxides used in non—volatile memory arrays and different technological alternatives will be exploited (i.e. Rapid Thermal Nitridation, Furnace Nitridation). In addition, a similar analysis will be carried out for gate oxides. Finally, some guidelines concerning the optimum selection of the furnace nitridation conditions will be given.
Microstructural Characterization of Copper Thin Films on Metallic Underlayers
Authors: Zielinski E. M. , Vinci R. P. , Bravman J. C. 
Published: April 2011

ABSTRACTGrain size distribution and texture of thin films of sputtered copper were characterized as a function of underlayer choice, deposition temperature and annealing temperature. For Cu deposited on Ta at room temperature and annealed at 100, 150, 200 and 250 °C, abnormal growth of the (100) orientation was observed for annealing temperatures above 150 °C, resulting in a bimodal grain size distribution. This orientation was also seen to grow abnormally for films deposited and annealed under identical conditions, but with a W underlayer. (100) growth for this case was observed at annealing temperatures as low as 100 °C. Abnormal grain growth was suppressed for Cu deposited on Ta at 150 °C and annealed to 250 °C. A bimodal grain size distribution was observed in a similar sample deposited on W under identical conditions, however, the abnormally growing orientation for this case was observed to be the (111) orientation, not the (100) orientation.
Dislocation Climb in the Electron Wind
Authors: Suo Z. 
Published: April 2011

ABSTRACTWhen a current flows in a conductor, the electron wind causes atoms to diffuse. This paper considers the consequences of such diffusion along dislocation cores. A dislocation climbing in a crystal is viewed as a non-equilibrium thermodynamic system to define the force that drives selfdiffusion along the core. Not only is a dislocation a mass-transport pipe, it also climbs and generates more dislocations—all in the electron wind. A prismatic loop moves like a rigid disk, as atoms electro-migrate along the core from one edge of the loop to the other. Each loop is therefore a mass carrier responding to an electric current. Interstitial and vacancy loops can be simultaneously generated and subsequently climb in the opposite directions. The process transports mass in single crystal or bamboo-like interconnects at moderate temperatures.
Critical Review of 1-Particle Models in Electromigration Resistance Change Modeling
Authors: Niehof J. , Graaff H.C. de , Mouthaan A.J. , Verwey J.F. 
Published: April 2011

ABSTRACTAn investigation is made into the capability of one-particle models in modeling electromigration-induced resistance changes. Analytically obtained solutions to the model equations are used to gain more insight into the vacancy distribution as a result of the applied boundary conditions. These solutions are then used to determine the resistance change modeling capabilities of three types of one-particle models.
The Edge Delamination Test: Measuring the Critical Adhesion Energy of Thin-Film Coatings, Part II: Mode Mixity & Application
Authors: Shaffer Edward O. , Sikorski Scott A. , McGarry Frederick J. 
Published: April 2011

ABSTRACTThe edge delamination test (EDT) is being developed to measure the critical energy required to cause a thin film, under biaxial tensile stress, to debond from a rigid substrate[1]. The test uses circular features etched through biaxially stressed films adhered to a rigid substrate. If the stress is large enough, a stable debond ring grows radially about the feature. We use a finite element analysis to model the test, solving for the applied strain energy release rate as a function of crack length, feature hole radius and other geometrical parameters. The model identifies both mode I and mode II components of the strain energy release rate, and agrees with previous analytical solutions for the total debond energy. However, the model predicts, with a very refined mesh at the crack tip, the fracture process is pure mode I. To explore this result, critical strain energy release rates from the EDT and the island blister test (IBT) are compared. This agreement supports the model prediction that the failure process in the EDT is modeI peeling.
Water Adsorption at Polymer/Silicon Wafer Interfaces
Authors: Wu Wen-Li , Kent Michael S. 
Published: April 2011

ABSTRACTNeutron reflectivity (NR) was applied to measure the concentration of water at the buried interfaces between polymer and silicon single crystal wafers. In the polyimide samplesexcess water was discovered within 30 Å of the silicon/polymer interface,where the water concentration reached 17% (by volume) for the samples without a couplingagent and 12% for the ones with coupling agent. Beyond the interface, the water concentration was measured at 2-3%, which is typical of bulk polyimide. Excess water was alsofound at the silicon/epoxy interface; more than 30% water was found within 150Å of the interface in the samples with their interface precoated with a coupling agent.The equilibrium moisture content in bulk epoxy used in this study is about 6%. The aboveresults demonstrate conclusively the unique power of NR in determining water concentration near a buried interface, and provide the first quantitative evidence for a water concentration profile which peaks in the interface region.