bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large and Stable Field-Emission Current from Heavily Si-Doped AlN Grown by MOVPE
Authors: Kasu Makoto , Kobayashi Naoki 
Published: April 2011

ABSTRACTWe investigated electron field emission (FE) from heavily Si-doped AlN grown by metalorganic vapor phase epitaxy. We found that, as the Si-dopant density increases, the threshold electric field decreases, which indicates that electrons are supplied to the surface effectively as a result of Si doping. We show that heavily Si-doped AlN has a maximum FE current of 347 μA (the maximum current density of 11 mA/cm2), stable FE current (fluctuation: 3%), and a threshold electric field of 34 V/μm. We observed visible light emission (luminance: about 1200 cd/m2) from phosphors excited by the field-emitted electrons.
Silicon Field Emitter Array by Fast Anodization Method
Authors: Fung Y.M. , Cheung W.Y. , Wilson I.H. , Xu J.B. , Wong S.P. 
Published: April 2011

ABSTRACTA new fast fabrication method entailing, two step anodization of silicon with different HF solutions was used to form a high aspect ratio silicon Field Emitter Array on n-type silicon (resistivity of 0.01cm). A Silicon oxide mask was used to define the field emitter array. The silicon substrate was pre-anodized with low current density for 1 minute in the dark and then anodized in HF:H2O:Ethanol solution. Finally, the porous silicon was removed by isotropic solution etching. The turn-on voltage of the fabricated field emitters was approximately 27V/μm when the emission current density reaches 1μA/cm2. This compares with the turn-on field of about 35V/μm on silicon tip array fabricated by using an isotropic etching solution of HNO3. We obtained field emitter arrays with good uniformity and reproducibility.
Field Emission Structure with Shottky-Barrier Electrode
Authors: Genelev Andrey P. , Levitsky Alexey A. , Zasemkov Vladimir S. 
Published: April 2011

ABSTRACTWe analyze a non-traditional version of semiconductor field emission structure, based on silicon cones arrays and destined for application in low-voltage vacuum microelectronics devices. In proposed construction, the gate electrode is used as Shottky-barrier contact on silicon tips. Due to Shottkybarrier contact we have obtained depletion layer in tip body under the gate electrode. Therefore variation of the gate electric potential provides the emitter current modulation. Experimental structures were fabricated with about 28000 silicon cones per 1 mm2 by reactive ion etching through a silica mask. Using a quasi two-dimensional model, we have computed these emitter structures. The model takes into account non-uniformity of silicon cone cross-section. Here, we study the influence of emitter tips parameters on the structure performance. Initial results prove the possibility of cathode current electric control with the gate electrode potential. Additionally we have obtained some other electric parameters of the emitter with the Shottky-barrier contact. The results of numerical analysis and experimental study provide a guide for design of proposed field emitter structure.
Field emission from heterostructured nanoseeded diamond and nanocluster carbon cathodes
Authors: Satyanarayana B.S. , Nishimura K. , Hiraki A. , Milne W.I. 
Published: April 2011

ABSTRACTNovel heterostructured cold cathodes made of nanoseeded diamond and cathodic arc process grown nanocluster carbon films, were studied. The nanocrystalline diamond with varying diamond concentration was first coated on to the substrate. The nanocluster carbon films were then deposited on the nanoseeded diamond coated substrates using the cathodic arc process at room temperature. The resultant heterostructured microcathodes were observed to exhibit electron emission currents of 1μA/cm2 at low fields of 1.2 - 5 V/μm. Further some of the samples seem to exhibit I-V characteristics with a negative differential resistance region at room temperature conditions. This negative differential resistance or the resonant tunneling behaviour was observed to be dependent on the nanoseeded diamond concentration.
Work function of carbon nanotubes
Authors: Shiraishi Masashi , Ata Masafumi 
Published: April 2011

AbstractThe work functions of multi- and single-walled carbon nanotubes are found to be 4.95eV and 5.10eV respectively. The measurements were carried out using the photoelectron emission (PEE) method, which allows easy and precise measurements to be made in air. We have found that the work function of the nanotubes is 0.1–0.2eV larger than that of highly oriented pyrolytic graphite (HOPG) of which the valence state is σ–Φ orthogonal. This result is ascribable to reflection of the σ–Φ⊏ mixed valence state in the case of carbon nanotubes. The experimental data were well reproduced in ab-initio calculations on planar and cylindrical conjugated states.
Monte Carlo Simulation of Amphiphile Self-Assembly during Dip Coating
Authors: Rankin Stephen E. , Malanoski Anthony P. , van Swol Frank 
Published: April 2011

AbstractFascinating nanostructured porous materials have recently been synthesized by evaporation-driven coassembly of ceramic precursors and amphiphiles. To expand our understanding of this process, we examine the influence of interfaces on self-assembly process using equilibrium lattice-based Monte Carlo simulations of ternary amphiphile-solvent mixtures. The simulations are able to predict the existence of all significant lyotropic mesophases, including lamellae, hexagonal closepacked cylinders, and cubic phases such as the gyroid. In the presence of walls that attract the majority solvent, the amphiphiles are confined to a smaller region of space, and experience a higher local concentration than the bulk concentration. This can lead to early transitions between mesophases. On the other hand, when the surface repels the majority solvent, amphiphiles tend to adsorb at the walls, and the local effective concentration in solution is lower. This can delay mesophase formation. When the amphiphile concentration is high enough that mesophases form in the bulk solution, however, either type of strongly attracting wall will align the mesophase (lamellae or hexagonal channels) parallel to the walls. In contrast, neutral walls (with no preferential interaction with either component) align mesophases perpendicular to themselves, which could be an interesting route to pores aligned normal to a film.
Nanosphere Lithography: Self-Assembled Photonic and Magnetic Materials
Authors: Haes Amanda J. , Haynes Christy L. , Van Duyne Richard P. 
Published: April 2011

AbstractEarly work with size-tunable periodic particle arrays (PPAs) fabricated by nanosphere lithography (NSL) demonstrated that the localized surface plasmon resonance (LSPR) could be tuned throughout the visible region of the spectrum. Further developments of the NSL technique have produced a myriad of nanoparticle configurations. Presented in this paper are several array types and examples of their utility in current applications. Both the sensitivity and tunability of the LSPR have been firmly established using single layer PPAs. Magnetic force microscopy (MFM) has been used to show that double layer PPAs act as single domain magnets and give strong MFM contrast. Angle-resolved NSL has produced nanogap and nano-overlap structures with manipulation resolution of one nanometer. Nanowell structures extend the original twodimensional structure into the third dimension. Exploitation of this flexible, materials-general NSL technique allows for investigation of the catalytic, electrochemical, magnetic, optical and thermodynamic properties of nanoparticles.
New Method For First Principles Modeling of Electron Transport through Nanoelectronic Devices.
Authors: Brandbyge Mads , Stokbro Kurt , Taylor Jeremy , Mozos Jose-Luis , Ordejón Pablo 
Published: April 2011

AbstractIn this paper we present a new theoretical method for modeling electron transport through nanostructures under non-equilibrium conditions. The electronic structure of the nanostructures are modeled from first principles and are described selfconsistently under the non-equilibrium conditions by means of a Green's function technique. The method is used to calculate the electron transport through benzene-dithiolate connected to two gold chains.
Sub-100 nm Patterning of Aluminum Film by AFM Local Oxidation
Authors: Notargiacomo Andrea , Foglietti Vittorio , Evangelisti Florestano 
Published: April 2011

AbstractWe have investigated the local oxidation of an aluminum film to fabricate aluminum and aluminum oxide masks on Si and SiGe substrates. The local oxidation is made by negatively biasing the probe of an atomic force microscope operating in contact mode. The masks are defined by removing the unwanted material using highly selective etching solutions at room temperature. The produced aluminum-based masks can withstand reactive ion etching processes using fluorinated gases mixtures. We report examples of sub-100 nm pattern transfer on the substrate using the AFM fabricated masks. Preliminary observations suggest to use the sputtered aluminum films for which the anodization is found more efficient than for e-beam evaporated aluminum.
Growth Mechanism of Chains of Silicon Nanocrystallites
Authors: Kohno Hideo , Tanaka Koji , Takeda Seiji 
Published: April 2011

AbstractThe growth mechanism of chains of silicon nanocrystallites was investigated. Energy-filtered transmission electron microscopy observations provided strong evidence that the chains were formed as a result of surface oxidation of silicon nanowires. In addition, the periodic instability in the wetting property of molten catalysts was simulated numerically.
Chemical stability studies of thermally-carbonized porous silicon
Authors: Salonen J. , Lehto V-P. , Björkqvist M. , Laine E. , Niinistö L. 
Published: April 2011

AbstractWe have studied chemical stability of thermally-carbonized porous silicon (PS). The initial hydrogen termination of PS has been replaced by carbon using thermal dissociation of acetelyne molecules. This kind of carbonized surface has been found to be at least as stable in humid atmosphere as a thermally-oxidized PS surface. It is also found to be stable in an aqueous KOH and HF. In-vitro studies of tissue compatible in simulated human fluid indicate improved stability and that the carbonized surface could be bioactive.
Diffusion Length Measurements of Minority Carriers in Si-SiO2Using the Photo-Grating Technique
Authors: Posada Y. , Balberg I. , Fonseca L.F. , Resto O. , Weisz S.Z. 
Published: April 2011

AbstractWe have studied the microstructure, the transport and the phototransport properties of the Si crystallites network in Si-SiO2composites. We have found that in our co-sputtered samples the average crystallite diameter, d, decreases from 40 to 5 nm as the content of the silicon, x, decreases from 80 to 40 volume%, and that the percolation of the network sets is at x ≈ 40 vol%. A simultaneous study of the photoluminescence (PL) shows the, quantum confinement, expected red shift of its peak with increasing d. On the other hand the very strong observed decrease of the PL intensity with x is interpreted here as due to a deconfinement effect that is dominated by the increase in the cluster size of connected Si crystallites. The results suggest that a closed random packing of the Si crystallites will be the preferred network for high intensity electroluminescence.
Modeling Carrier Transport in Oxide-Passivated Nanocrystalline Silicon Leds
Authors: Hirschman Karl D. , Fauchet Philippe M. 
Published: April 2011

AbstractThis report presents an investigation on carrier transport in LED structures based on oxide passivated nanocrystalline silicon (OPNSi), formed by oxidation of porous silicon. This material, like its precursor, can luminesce quite efficiently while demonstrating several advantages in stability (i.e. chemical, thermal, electrical and electroluminescence). OPNSi can be best described as a porous glass structure with defects that facilitate transport, and remaining embedded nanocrystals of silicon that support light emission. Although this study does not provide a direct measurement of the density of states in OPNSi, the following transport study suggests a high density of states having a broad energy distribution that readily exchange charge with the silicon electrodes. Experimental data also suggests the existence of deeper trap centers that do not facilitate transport, yet influence transport behavior significantly. The device operation is explained by bipolar injection from an electron-injection cathode and a hole-injection anode into the semi-insulating OPNSi layer. The device is modeled as a “field effect diode”, where untraditional concepts are applied in the interpretation of experimental observations. Extensive electrical characterization of OPNSi LEDs has lead to the development of a comprehensive transport model that is self-consistent with all experimental observations.
Prorerties of Nanostructured Porous Semiconductors Studied Via Noise Spectroscopy
Authors: Parkhutik Vitali 
Published: April 2011

SummaryFormation of porous layers via localized corrosion of semiconductors is a reliable method to produce nano-structured semiconducting materials. The formation process is assisted by strong fluctuations (noise) of the anodic potential or current applied to the corroding material. Electrical and optical characteristics of nanoparticles are also quit noisy. The noise is a result of heterogeneity of the electrochemical reactions involved into the formation of pores and pits, transient phenomena in the formed porous layers, their exchange by energy with environment, etc. Therefore, analyzing the noise would be useful to understand the nature of the formation processes and properties of nanoparticles.Here we present the results of studying the formation of porous silicon and electrical properties of the formed porous layers with the help of so-called Flicker-Noise Spectroscopy (FNS), method allowing to quantify and analyze the information contained in noisy signals. The method is different from existing approaches in that it allows not only to represent the noisy signals but estract physically meaning information from them. It is shown that using the FNS approach one can extract useful information on the kinetics of the electrochemical and electrical processes.
Analyses of Ballistic Electron Transport in Nanocrystalline Porous Silicon
Authors: Kojima Akira , Sheng Xia , Koshida Nobuyoshi 
Published: April 2011

AbstractThe characteristics of ballistic electron transport in porous silicon (PS) are investigated in terms of the electron emission from PS diodes and the energy distribution of emitted electrons. The energy distributions show a behavior of ballistic electron emission that is quite different with the Maxwellian distribution. This is clearly observed at low temperatures below 150 K where the electrical conduction in PS is dominated by the tunneling mode. At 100 K, the peak position of distribution curve becomes more close to the energy corresponding to the energy gain expected from ballistic transport without any scattering losses. The simulated energy distribution suggests that the electrons having higher energies in a non-equilibrium state travel ballistically in PS via field-induced tunneling process. These results support that electrons can travel ballistically in nanocrystalline layer under a high electric field. The observed ballistic transport indicates the further technological potential of silicon nanocrystallites.
A Novel Solid-State Light-Emitting Device Based on Ballistic Electron Excitation
Authors: Nakajima Y. , Kojima A. , Koshida N. 
Published: April 2011

AbstractThe concept of a novel solid-state light-emitting device is proposed on a basis of our previous report that the nanocrystalline porous silicon (PS) diode with a well-controlled structure operate as an efficient ballistic electron emitter. This device is composed of a semitransparent thin Au film, a fluorescent thin film, a PS layer, and n-type Si substrate. When a positive bias voltage is applied to the Au electrode, visible luminescence is emitted of which band corresponds to that of the deposited fluorescent material. The optoelectronic characteristics suggest that the light emission is based on direct excitation of fluorescent film by ballistic electrons generated in the PS layer. This result indicates another possibility of nanocrystalline silicon for photonic applications.
Photoluminescence from amorphous SiO2/Silicon/amorphous SiO2single quantum well structures
Authors: Wang Y.Q. , Ishikawa Y. , Shibata N. 
Published: April 2011

AbstractAmorphous silicon dioxide/silicon/amorphous silicon dioxide single quantum well structures were fabricated by oxygen implantation followed by thermal oxidation. No photoluminescence (PL) was observed from the as grown samples. We found that annealing in hydrogen allows the single quantum well (SQW) structures to emit two-peak (blue and yellow) PL at room temperature (RT). The blue PL (2.9 eV) does not change with the thickness of Si layers or the temperature. The yellow peak varied from 2.0 eV to 2.4 eV with thinning of the Si layer from 5 nm to 0.5 nm. Lowering the temperature also changed the yellow peak position of the 1.5 nm Si-SQW structure from 2.3 eV (RT) to 2.6 eV (8.4 K). We conclude that the blue PL is from SiO2 and the yellow PL is caused by a recombination process in the Si-SQW.
The Effect of Surface Roughness on Photoluminescence of Porous Silicon
Authors: Ogawa Shunsuke , Uehara Nobutomo , Ohmukai Masato , Tsutsumi Yasuo 
Published: April 2011

AbstractWe studied the effect of surface roughness of Si wafers on porous silicon by means of photoluminescence (PL), Fourier transformed infrared (FTIR) absorption and Raman spectroscopy. We prepared several kinds of Si wafers with a different surface roughness, and then the anodization was performed at a same condition. PL spectra show a blue shift with the increase of surface roughness. The particle size of porous silicon nanostructure becomes the smaller with increasing surface roughness at the same time. On the other hand, FTIR absorption spectra show no difference regardless of surface roughness. The PL emission dependent on the surface roughness originates from a quantum size effect. We infer that the surface roughness causes the concentration of the current during anodization in the area where the radius of the curvature at the surface is small.
A novel, nanocrystal (nc) based non-volatile memory device
Authors: Blauwe Jan W. De , Green Marty L. , Sorsch Tom W. , Weber Garry R. , Bude Jeff D. , Kerber Andi , Klemens Fred , Kim Young , Ostraat Michele L. , Flagan Richard C. , Atwater Harry A. 
Published: April 2011

AbstractThis paper describes the fabrication, and structural and electrical characterization of a new, aerosol-nanocrystal floating-gate FET, aimed at non-volatile memory (NVM) applications. This aerosol- nanocrystal NVM device features program/erase characteristics comparable to conventional stacked gate NVM devices, excellent endurance (>105 P/E cycles), and long-term non-volatility in spite of a thin bottom oxide (55-60Å). In addition, a very simple fabrication process makes this aerosol-nanocrystal NVM device a potential candidate for low cost NVM applications.
AC Operation of GaN:Er Thin Film Electroluminescent Display Devices
Authors: Heikenfeld J. , Steckl A. J. 
Published: April 2011

ABSTRACTThin-film electroluminescence has been obtained from GaN:Er deposited directly on amorphous dielectric layers. Electroluminescent device (ELD) structures consisting of a dielectric/GaN/dielectric were formed on p+-Si substrates. In contrast to previous GaN:Er ELDs which used epitaxial growth conditions on crystalline substrates and were operated under DC bias, these ELDs were operated under AC bias. A maximum luminance value of 300, 60, and 15 cd/m2 has been achieved from GaN:Er and AlGaN:Er AC-ELDs biased at 180 V and 100, 10, and 1 kHz, respectively. The emission spectra, which originate from Er3+ 4f-4f transitions, consist of dominant visible emission at ∼537/558 nm and infra-red (IR) emission at 1.5 μm. A violet emission peak at 415 nm indicates that hot carriers can gain up to ∼3 eV energy for an applied voltage corresponding to 1.5 MV/cm applied field. The emitted intensity initially increases linearly with frequency, followed by a trend towards saturation. The frequency for 3 dB reduction from the linear relation is at ∼65 kHz for visible emission and ∼8 kHz for infrared emission. The saturation trends can be explained in terms of the spontaneous emission lifetimes of the visible (∼10 μs) and IR (∼1ms) Er3+ emissions.
Electrical Properties of InN Grown by RF-MBE
Authors: Saito Yoshiki , Teraguchi Nobuaki , Suzuki Akira , Yamaguchi Tomohiro , Araki Tsutomu , Nanishi Yasushi 
Published: April 2011

ABSTRACTInN films with excellent surface morphology were grown by controlled the V/III ratio of InN epitaxal layer. It was found they were single crystal of InN films with wurtzite structure by X-ray diffraction (XRD) measurement and reflection high-energy electron diffraction (RHEED) observation. Hall mobility as high as 760 cm2/Vs was achieved for InN film grown at 550°C with 240 W of RF plasma power with a carrier density of 3.0×1019 cm−3 at room temperature. To our knowledge, this electron mobility is the highest value ever reported.
Profiling electric fields in GaN/InGaN/GaN single quantum wells by electron holography
Authors: Cai Juan , Mccartney M. R. , Ponce F. A. 
Published: April 2011

ABSTRACTWe use electron holography to profile the local internal potential due to spontaneous polarization and piezoelectric effects in strained quantum well structures of wurtzitic group III nitrides. Profiles of the electrostatic potential across a GaN/InxGa1−xN/GaN quantum well structure show the existence of internal electric fields of about –2.2 ± 0.6 MV/cm, and a potential drop across the quantum well of 0.6 ± 0.16 V. The electric fields indicate an average indium composition of 15% in the quantum well, for a thickness of 2.7 nm. This indium composition compares well with measurements by energy-disperse spectroscopy of 18 ± 2 %. Screening effect is not observed under these experimental conditions.
Group-III Nitride Quantum Heterostructures Emitting in the whole Visible Range
Authors: Grandjean Nicolas , Damilano Benjamin , Massies Jean 
Published: April 2011

ABSTRACTGroup-III nitride quantum wells (QWs) and quantum dots (QDs) have been grown by molecular beam epitaxy (MBE). Their optical properties are shown to be governed by the presence of a huge internal polarization field. For example, GaN/AlN QDs emit from the blue to the orange due to the giant quantum confined Stark effect (QCSE) induced by a built- in electric field of 4 MV/cm. Another consequence of the QCSE is to drastically reduces the oscillator strength of the ground state transition and thereby to increase by several orders of magnitude its radiative lifetime. Despite the very large density of dislocations in nitride layers, which induce non-radiative recombinations, carrier localization enhances the photoluminescence (PL) efficiency. This is demonstrated by GaN/AlN QDs grown on silicon substrates exhibiting strong PL intensity at room temperature. InGaN/GaN QWs with In composition of 20% also display 300 K PL peaking through the whole visible spectrum (0.4-0.66 νm). This is achieved by varying the QW thickness from 1.5 to 5.5 nm, the red-shift resulting from an internal electric field of 2.5 MV/cm. For InGaN/GaN QWs emitting at 2.8-2.9 eV, the PL efficiency at 300 K is larger than 10 %. This is ascribed to carrier localization, which is not due to InGaN phase separation that would form QDs, as revealed by transmission electron microscopy. Another origin of the carrier localization in InGaN/GaN QWs is then discussed.