bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of Porous Silicon Injection Electroluminescence
Authors: Paul Maruska H. , Namavar F. , Kalkhoran N. M. 
Published: March 2011

ABSTRACTWe discuss the operation of porous silicon light-emitting diodes prepared as heterojunctions between n-type In2O3:Sn (ITO) and p-type silicon nanostructures, exhibiting quantum confinement effects. The transparent ITO affords light emission through the top surface of the device, as well as providing passivation and hence long term stability. We describe a model for the injection of minority carrier electrons into the porous silicon regions, which results in the emission of yellow-orange DC electroluminescence. A detailed study of the forward bias current-voltage characteristics of the devices will be given, which allows calculations of the densities of interface states. A tendency to pin the hole fermi energy near the neutral level, φ0, is shown to control the extraction of majority carriers. Methods for improving LED efficiency by alleviating a parasitic shunt current path through interface states will be addressed.
Visible Electroluminescence from Pn Junction Type μc-Sic/ Porous Si / c-Si Structures
Authors: Futagi T. , Matsumoto T. , Katsuno M. , Ohta Y. , Mimura H. , Kitamura K. 
Published: March 2011

ABSTRACTWe have fabricated two kinds of n-type microcrystalline silicon carbon (μc-SiC) / porous silicon (PS) / p-type crystalline silicon (c-Si) pn junctions and demonstrated a visible light emission from them. We have observed three types of visible light emission; an uniform red light emission at a forward current above 12mA/cm2 for the pn junction using a 0.2–0.4 Qcm c-Si substrate, and a very weak white light emission at a forward current of about 90 mA/mm2 and a strong orange-red light emission at a forward current from 200 to 619 mA/mm2for the pn junction using a 3.5–4.5 Ωcm c-Si substrate.
Role of Hydrogenated Surface in the Photoluminescence of Porous Silicon
Authors: Hirao Masahiko , Uda Tsuyoshi , Murayama Yoshimasa 
Published: March 2011

ABSTRACTOptical properties of hydrogenated silicon clusters are investigated by density functional pseudopotential calculation. Transitions between the band-edge orbitals are allowed, in contrast to the indirect gap in bulk silicon. The energy gaps of hydrogenated silicon particles of 15 to 30 Å in diameter are estimated to be 2.0 to 1.5 eV. When the cluster is dehydrogenated, localized states related to dangling bonds appear in the mid-gap, which decrease the photoluminescence intensity. These results agree with much experimental evidence and suggest that the photoluminescence of porous silicon is attributable to hydrogenated silicon particles.
Microcrystalline Silicon in a-SI:H Based Multljunction Solar Cells
Authors: Yang Liyou , Chen L. , Wiedeman S. , Catalano A. 
Published: March 2011

ABSTRACTMaterials issues central to the application of microcrystalline silicon (μc-Si) doped layers in a-Si:H based solar cells are discussed, which include: (1) characterization of ultra-thin layers to be incorporated in the device, and (2) methods to promote nucleation of μc-Si on desired substrates within a thickness on the order of ∼100Å. Successful application of (μc-Si) in multijunction a-Si:H based solar cells are demonstrated.
Microcrystalline Silicon Prepared by VHF-GD: Structure, Transport and Optical Properties
Authors: Finger F. , Carius R. , Hapke P. , Prasad K. , Fliickiger R. 
Published: March 2011

ABSTRACTDoped and compensated microcrystalline silicon prepared by Very High Frequency Glow Discharge has been investigated by optical spectroscopy and by temperature dependence of the electrical conductivity. Raman spectroscopy confirms the microcrystalline nature of all samples with only small changes of the crystalline volume fraction upon doping. Strong absorption in the infrared region, which correlates with the conductivity, is attributed to free carrier absorption. As a function of temperature the conductivity of all samples shows a deviation from a purely activated behaviour. Consequences of this observation for transport mechanisms are discussed.
Conductance in Microcrystalline BbxCx/Si Heterojunction Diodes
Authors: Lee Sunwoo , Ton Thuong , Zych D. , Dowben P. A. 
Published: March 2011

ABSTRACTPlasma-enhanced chemical vapor deposited boron carbide (B1-xCx) thin films are shown to be a potential electronic material suitable for high temperature devices. The boron carbide films make excellent p-n heteroj unction diodes with /i-type silicon substrates. The B1-xCx/Si heteroj unction diodes are demonstrated to have rectifying properties at temperatures above 200°C and reverse current is strongly dependent on the energy of the band gap of the boron carbide films.
Microcrystalline Silicon by Dc Magnetron Sputtering: Growth Mechanisms
Authors: Feng G. F. , Katiyar M. , Yang Y. H. , Abelson J. R. , Maley N. 
Published: March 2011

ABSTRACTWe have used real-time, in situ spectroscopie ellipsometry (SE) and infrared reflectance (IR) to study microcrystalline silicon (μc-Si) formation in reactive magnetron sputtering (RMS). μc-Si growth occurs at high hydrogen partial pressures and moderate substrate temperatures. We use IR studies and SE studies of film growth on rough surfaces, respectively, to show that these conditions lead to high hydrogen coverage of the film surface and high effective surface diffusivity. The interface region is amorphous and its thickness decreases with deposition rate. For a fixed growth flux, we observe a 30% decrease in the deposition rate of μc-Si relative to the amorphous interface region. This could be due to increased etching or decreased sticking coefficients during microcrystalline growth.
Hydrogen Configurations in Microcrystallized Sputtered Amorphous Silicon.
Authors: Lusson L. , Elkaim P. , Cuniot M. , Ballutaud D. , Rizk R. , Dixmier J. 
Published: March 2011

ABSTRACTSuccessive deuterium diffusion and effusion experiments are performed on undoped microcrystalline silicon obtained from thermally crystallized sputtered amorphous silicon thin films. The effect of prior incorporation of deuterium during the amorphous film growth on the crystallization mechanism and on the microcrystalline film quality is probed by the use of the post hydrogenation procedure. In connection with the deuterium solubility as provided by secondary ion mass spectroscopy (SIMS) profiling, the analysis of the effusion spectra suggests the existence of large cavities in the crystallized a-Si:D films, containing most probably molecular hydrogen. They are absent in the corresponding crystallized non-deuterated a-Si films. Other deuterium configurations seem to be present in both kinds of samples such as weakly bonded deuterium in small clusters and at grain boundaries.
Structure and Morphology of μic-SiC:H films Produced by PECVD
Authors: Demiehelis F. , Crovini G. , Pirri C. F. , Tresso E. , Battezzati L. , Rava P. 
Published: March 2011

ABSTRACTFilms of μc-Si:H have been deposited in a conventional PECVD system in order to investigate their structural and morphological properties. They consist of a mixed phase of Si crystallites (50–200 Å), surrounded by grain boundaries, and amorphous regions. In this paper we report results obtained by different characterization techniques which have been used to deduce grain size, microcrystallinity fraction and composition of the crystalline, amoiphous and grain boundary. The amorphous matrix can be considered a covalent network where tetrahedrically coordinated carbon atoms, with 1 on 9 bonds terminated by hydrogen, exist. They form a distribution of large aromatic clusters containing a great number of aromatic rings such as to remarkably reduce the number of network terminators (hydrogen atoms).
Solute Binding at Void Surfaces in Silicon and germanium
Authors: Myers S. M. , Bishop D. M. , Follstaedt D. M. , Stein H. J. , Wampler W. R. 
Published: March 2011

ABSTRACTThe strongly exothermic reactions of H and Cu with internal surfaces in Si and Ge were examined in experiments employing ion implantation, ion-beam analysis, transmission electron microscopy, and infrared spectroscopy. The dissociation energy of the Si-H surface bond was determined to be 2.6±0.1 eV, so that the monohydride is more stable than molecular H2, whose dissociation energy per atom is 2.26 eV. Initial experiments indicate a dissociation energy for the Ge-H surface bond of =1.9 eV. Copper is bound to the Si surface with an energy of 2.2±0.2 eV relative to solid solution, as compared to a reported binding energy of 1.5 eV for Cu in the precipitated Cu3Si phase.
Photoluminescence in B-doped μc-Si:H
Authors: Gu S. Q. , Viner J. M. , Taylor P. C. , Williams M. J. , Turner W. A. , Lucovsky G. 
Published: March 2011

ABSTRACTPhotoluminescence (PL) has been investigated in hydrogenated microcrystalline silicon (μc-Si:H) samples as a function of boron doping for films prepared by remote plasma enhanced chemical vapor deposition. When the dark conductivity a is below about 10-5 S/cm, the PL spectra exhibit a shape which is close to that of the so-called band tail PL in undoped hydrogenated amorphous silicon (a-Si:H) at 77 K. When a increases, the PL intensity decreases at 77 K. For samples with a on the order of 10-3 S/cm, the PL spectra show only a narrow, low energy PL band which peaks around 0.8–0.9 eV. In these samples, the PL at higher energy is essentially not observable. This trend is similar to that which occurs in doped a-Si:H. However, for higher doping levels (σ ∼ 1 S/cm) the PL in μc-Si:H, although very weak, exhibits a broad band which contains intensity at higher energies. The absorption spectra in these samples, as measured by photothermal deflection spectroscopy (PDS), show the same relationships with the corresponding PL spectra as do the PDS spectra in doped a-Si:H.
Properties and Production Mechanism of Low-Temperature Deposited CAT-CVD Poly-Silicon films
Authors: Matsumura Hideki , Hosoda Yoichi , Furukawa Seijiro 
Published: March 2011

ABSTRACTPoly-silicon films are obtained at temperatures as low as 400 °C by the catalytic chemical vapor deposition (cat-CVD) method, in which deposition gases are decomposed by the catalytic or pyrolytic reactions with a heated catalyzer near substrates. It is found that there are roughly two modes of deposition conditions such as low gas pressure mode and high gas pressure mode for obtaining poly-silicon films, and also that the Hall mobility of the cat-CVD poly-silicon films of low gas pressure mode sometimes exceeds over 100 cm2/Vs.
Photoluminescence from Microcrystalline Silicon and Related Materials
Authors: Rlickschloss M. , Landkammer B. , Ambacher O. , Vepřek S. 
Published: March 2011

ABSTRACTIntense photoluminescence has been obtained from nanocrystal-line silicon prepared in completely dry processing by the optimizing the crystallite size and the chemical passivation of the grain boundaries due to a controlled postoxidation of the plasma deposited films.
Excimer Lasbr Induced Crystallization of thin Amorphous Si Films on SiO2: Implications of Crystallized Microstructures for Phase Transformation Mechanisms
Authors: Kim H. J. , Im James S. , Thompson Michael O. 
Published: March 2011

ABSTRACTUsing planar view transmission electron microscope (TEM) and transient reflectance (TR) analyses, we have investigated the excimer laser crystallization of amorphous silicon (a-Si) films on SiO2. Emphasis was placed on characterizing the microstructures of the single-shot irradiated materials, as a function of the energy density of the laser pulse and the temperature of the substrate. The dependence of the grain size and melt duration as a function of energy density revealed two major crystallization regimes. In the low energy density regime, the average grain size first increases gradually with increases in the laser energy density. In the high energy density regime, on the other hand, a very fine grained microstructure, which is relatively insensitive to variations in the laser energy density, is obtained. In addition, we have discovered that at the transition between these two regimes an extremely small experimental window exists, within which an exceedingly large grain-sized polycrystalline film is obtained. We suggest a liquid phase growth model for this phenomenon, which is based on the regrowth of crystals from the residual solid islands at the oxide interface.
Large-Grain Doped Poly-Si Films Fabricated Using New Excimer Laser Annealing Technique
Authors: Iwata Hiroshi , Nohda Tomoyuki , Ishida Satoshi , Kuwahara Takashi , Sano Keiichi , Kuriyama Hiroyuki , Noguchi Shigeru , Hanafusa Hiroshi , Kiyama Keiichi , Tsuda Shinya , Nakano Shoichi , Kuwano Yukinori 
Published: March 2011

ABSTRACTThe grain size of phosphorous (P)-doped poly-Si film has been enlarged to about 5000 Å by controlling the solidification velocity of molten Si during ArF excimer laser annealing. The drastically enlarged grain has few defects inside the grain. It has been confirmed that control of the solidification velocity is effective for P-doped poly-Si similar to the case of non-doped poly-Si films. In addition, a sheet resistance of 80 Ω/□ (ρ = 4 × 10-4 Ω · cm) has been achieved for very thin (500 Å) films by recrystallizing PECVD P-doped a-Si films.
Nanocrystallites of Si Embedded in CaF2 by Molecular Beamepitaxy (MBE)
Authors: Taylor A. P. , Stokes K. , Wu Z. C. , Persans P. D. , Schowalter L. J. , LeGoues F. K. 
Published: March 2011

ABSTRACTThin films of CaF2 containing layers of Si nanocrystals were grown epitaxially on Si(111) substrates by MBE. When Si is deposited epitaxially on CaF2 it forms islands and, by choosing appropriate growth conditions, a composite of Si nanocrystals embedded in a CaF2 host crystal is obtained which we have observed with TEM. We varied the effective Si concentration in the composite region from 1% to 25%. The CaF2 could be grown with high crystal quality as demonstrated by ion channeling results which gave Ca xmin's as low as 4.7%. Raman spectra of the CaF2 containing Si nanocrystallites showed significant shifts toward lower energies. EUipsometry measurements were performed on a number of samples over a range of effective Si concentrations and Maxwell-Garnett effective medium theory was used to fit the data. A key technological advantage to this approach is that the epitaxial Si/CaF2 composite material is readily integrable into VLSI processing.
Si-Cluster Luminescence
Authors: Saunders Winston A. , Atwater Harry A. , Vahala Kerry J. , Flagan Richard C. , Sercel Peter C. 
Published: March 2011

ABSTRACTWe report on a technique for generating Si-clusters in the nanometersize regime. The cluster source is capable of generating micron-thick cluster films in a few minutes. The cluster films luminesce in thevisible and infrared. Source construction is discussed. Electron micrographs of the clusters are shown. Luminescence and optical absorption spectra for the clusters are presented.
Optical Properties of InGaAs/InP Quantum Wires Defined by High Voltage Electron Beam Lithography at 200 kV
Authors: Ils P. , Michel M. , Forchel A. , Gyuro I. , Speier P. , Zielinski E. 
Published: March 2011

ABSTRACTWe have fabricated and analyzed high quality InGaAs/InP quantum wires by electron beam lithography and wet chemical etching. In order to optimize the shape of the wet-etched wires different wire orientations were investigated. As results of the lithography process we obtain wire masks with widths down to 15 nm and etched wires with widths of the InGaAs layer of 18 nm.The wires were studied optically by means of photoluminescence spectroscopy. In contrast to dry etched wire structures the wet chemically etched wires show strong optical emission even for geometrical widths less than 25 nm. The weak decrease of the quantum efficiency with decreasing wire width indicates that there are no dead layers at the side walls of the wires, which is in contrast to previous studies on dry-etched structures. The photoluminescence energy of the InGaAs/InP wires is independent of the wire dimension down to widths of 50 nm. This indicates that a steep lateral potential in our structures is obtained due to the confinement by the semiconductor/vacuum transition at the etched surfaces. For wires with smaller widths an increasing blue shift of photoluminescence energy up to more than 30 meV is observed.
Studies of Quantum Dots Fabricated by Combining Aerosol and Plasma Etching Techiques
Authors: Samuelson Lars , Maximov Ivan , Gustafsson Anders , Liu Xiao , Seifert Werner , Hansson Hans-Christen , Wiedensohler Alfred 
Published: March 2011

ABSTRACTA new approach has been taken for the fabrication of Quantum Dot materials to be used for physics as well as for opto-electronics applications. We used a generation technique of ultrafine aerosol Ag particles which are deposited onto the surface of GalnAs/InP quantum well structures grown by Metal Organic Vapor Phase Epitaxy (MOVPE). The particles, ranging in size between 30 and 40 nm, are subsequently used as an etching mask. The Ag aerosol produced by homogeneous nucleation and can have a mean diameter in the range 2 – 100 nm. After size-selection, monodisperse particles with a very narrow size distribution are deposited onto the semiconductor surface at a density of about 109 cm-2. Low energy CH4/H/Ar Electron Cyclotron Resonance (ECR) plasma etching results in the formation of free-standing InP columns 50 to 80 nm in diameter and 120 to 280 nm in height. Their size and stability were found to be dependent on the etching conditions and the diameter of the particles. Low-temperature cathodoluminescence (CL) was used to evaluate the quantum dot structures fabricated by this technique.
Optical Properties of Metal Coated Particles
Authors: Haus Joseph W. , Zhou H. S. , Honma I. , Komiyama H. 
Published: March 2011

ABSTRACTMetal-coated particles of nanometer dimensions can exhibit unusual optical properties due to the local-field enhancement mechanism. However, the properties are affected by uncontrollable factors that degrade the expected performance. In this paper we report theoretical results of coating thickness variations and diffuse interface effects on the optical absorption and the nonlinear optical response of particles with a CdS core and a silver coating. The linear and nonlinear optical properties are discussed within the context of the effective medium theory for small volume fractions.
Piezoresistivity of Polycrystalline Diamond Films
Authors: Wur Der-Rern , Davidson Jim L. 
Published: March 2011

ABSTRACTPolycrystalline diamond film (PDF) is known for its high power, high temperature, and radiation hard potential. The interest in piezoresistivity of PDF is that it is a candidate for high temperature sensing (e.g., pressure sensor).Piezoresistivity measurements were taken of boron-doped PDF grown by microwave-plasma chemical vapor deposition(CVD). Three substrates, silicon, aluminum nitride and tungsten were used. Films were detached from these substrates, then attached to a ceramic substrate. The piezoresistivity varies, dependent on the original host substrate. For example, at room temperature, the PDF film from tungsten has a greater gauge factor, around 75. The carrier activation energy of this film, determined from log R(l/T), was nominally 0.25eV.Combining thick film technology and CVD processes, patterned B-doped PDF has been achieved monolithically on A1N substrates. The characteristics of this configuration is being investigated and will be presented.
Electrical and Optical Properties of Indium Doped Zinc Oxide Films Prepared by Atmospheric Pressure Chemical Vapor Deposition
Authors: Hu Jianhua , Gordon Roy G. 
Published: March 2011

ABSTRACTIndium doped zinc oxide films have been deposited from diethyl zinc, ethanol and trimethyl indium in the temperature range between 225°C and 450°C in a laminar flow atmospheric chemical vapor deposition reactor. Both doped and undoped films were crystalline. The doped films have electron density up to 9×1020 cm-3, conductivity up to 850 Ω-1cm-1, and mobility up to 8 cm2/Vs. The indium doping increases the average visible absorption from less than 1% to above 20%. The transparency and conductivity of indium doped zinc oxide films are lower than those of fluorine doped films.
Study of Solar Cells by Sem Dark Voltage Contrast
Authors: Mil'Shtein S. , Iatrolt S. , Kharas D. , Bell R. O. , Sandstrom D. 
Published: March 2011

ABSTRACTFor the first time the Scanning Electron Microscopy (SEM) Dark Voltage Contrast (DVC) technique was used to examine the field distribution in a solar cell made of polycrystalline silicon.The samples were cut off solar cells made of Edge-defined Film-fed Grown (EFG) Silicon and lapped at 2 and 5 degree angles. The DVC measurements were performed at forward, reverse, and zero bias conditions using a Hitachi S-570 SEM and a Kevex-8000 microanalyzer.The I-V curves were recorded to test the electric performance of the samples. We examined two groups of solar cells. One group of cells demonstrated, after regular processing, reasonable electrical performance and abrupt DVC profile. The other group was intentionally doped with titanium, which presumably was agglomerated in the p-n junction area thus degrading completely the electrical performance of the cells and weakening the electric field by a factor of 4–6.
Characterization of Porous Silicon: Structural, Optical and Electrical Properties
Authors: Badoz P. A. , Bensahel D. , Bomchil G. , Ferrieu F. , Halimaoui A. , Perret P. , Regolini J. L. , Sagnes I. , Vincent G. 
Published: March 2011

ABSTRACTThe aim of this paper is to provide a better understanding of photoluminescent porous silicon (PS) microstructure in relation to their electronic properties: absorption band edge shift1 and quantum confinement hypothesis1,2, dielectric constant evolution and electroluminescence characteristics.Results concerning the p type PS microstructure characterization by X ray diffraction and electron microscopy are presented showing a noticeable decrease in crystallite size and surface area with decreasing substrate doping and increasing porosity.The optical transmission of homogeneous free-standing PS layers of different porosities and substrate dopings is studied, showing no evidence of a direct energy gap in PS. On the contrary, a large blue shift of the optical absorption edge, taking into account the total Si mass content in the PS film, is demonstrated. This shift is well correlated with the crystallite size variations with porosity and substrate doping and is attributed to a quantum confinement of electronic wavefunctions in the nanocrystallites.On the other hand, ellipsometry measurements show the PS absorption to be little affected by the microcrystalline structure of the material in the 3.5–5 eV range, i.e. above the direct band gap of bulk Si. This indicates that, if confirmed, the quantum confinement strongly affects the PS joint density of states in the vicinity of the Si band edge and, as could be expected, to a much lesser degree near the edge of the confining potential.Capacitance voltage measurements of thin PS layers allow the determination of the dielectric constant which is shown to decrease with increasing porosity. This behavior is in reasonable agreement with theε values deduced from the transmission experiments in the near infrared. Furthermore, it is shown that this dependence on porosity is well accounted for by the Bruggeman effective medium approximation.Finally, recent results concerning visible light emission from solidstate porous silicon devices will be presented: I-V characteristics, electroluminescence intensity and dynamic, quantum efficiency and device ageing.