Raman and Ellipsometric Studies of Delta-Doped GaAs

1992 ◽  
Vol 261 ◽  
Author(s):  
H. Yao ◽  
E. F. Schubert ◽  
R. F. Kopf
Keyword(s):  
Spectroscopic Ellipsometry ◽  
High Energy ◽  
Plasmon Mode ◽  
Gaas Sample ◽  
Similar Frequency ◽  
Layer Spacing ◽  
Coupled Mode ◽  
Spatial Quantization ◽  
Electron Distributions ◽  
Energy Subbands

ABSTRACTGaAs (100) samples with multiple δ-doped layers (N2D=∼2×1013/cm2) were studied by Raman scattering (RS) and spectroscopic ellipsometry (SE). A quasithree- dimensional (3D) plasmon-phonon coupled mode (L+), probed at λ= 514.5 nm, from a 9-layer δ-doped GaAs with layer-spacing of 100 Å, was observed at ∼895 cm−1. At similar frequency, a plasmon mode was also detected from another GaAs sample with the same δ-doping periods but doubled layer-spacing (200 Å). This provides evidence of spatial quantization of the electron distributions in δ-doped GaAs. The equivalent 3D electron concentration, estimated from the Raman plasmon mode, is ∼1.1×1019/cm3. The presence of the 3D plasmon mode from a quasi-two-dimensional (2D) electron gas is possibly contributed by the electrons in the high energy subbands in the V-shaped potential well of the δ-doped GaAs. The pseudodielectric function <ε>= <ε1>+i<ε2> of this δ-doped GaAs sample was measured by spectroscopic ellipsometry (SE), from an unoxidized surface in an ultrahigh vacuum (UHV) chamber, in the range of 1.5 to 5.0 eV. Compared with uniformly doped GaAs, our SE data indicates a reduced broadening of the optical transitions between the E1 and E1+Δ1, energies due to the δ-doping.

Metal Atom Routes to Metal-Based Clusters in Polymers

1988 ◽  
Vol 131 ◽  
Author(s):  
Mark P. Andrews ◽  
Mary E. Galvin ◽  
Sharon A. Heffner
Keyword(s):  
Polymer Composites ◽  
Metal Atom ◽  
Chemical Reduction ◽  
Incident Light ◽  
High Energy ◽  
Plasmon Mode ◽  
Ambient Temperatures ◽  
Metal Vapors ◽  
Precursor Molecules

ABSTRACTPast syntheses of polymer composites have largely evolved from chemical reduction or thermal decomposition of organometallic or inorganic precursor molecules in polymers, or plasma and thermal co-deposition of metal vapors and carbonaceous free radicals. Our approach involves the site-specific capture of metal atoms deposited in vacuum to give isolated, high energy mononuclear organometallic centers within a polymer film. These centers can be converted at ambient or sub-ambient temperatures (ie, below the polymer glass transition temperature) to, for example, metal oxide microclusters.We describe the results of our studies of a prototypical system involving chromium atoms and their conversion to corundum-type oxide microclusters in arene-functionalized polymer films. Thus Cr was deposited into 150 K liquid tetrahydrofuran solutions of polystyrene or poly(styrene-isoprene-styrene) triblock, spun in vacuo as thin films on the surface of a rotating glass cryostat. Evidence from epr spectrscopy shows that the resulting polymer-anchored (inter/intra-chain) bis(arene)Cr sandwich complex is locally mobile in the macroscopically rigid film at room temperature. The Cr atom is discharged from the rings by subsequent reaction with oxygen diffused into the film. Although α Cr2 O3 is a classic twosublevel antiferromagnet that is not epr active above 308 K, we observe an intense signal even at 77 K in these films. Cr2O3 microclusters are indicated, and these are confirmed by in situ measurements of the oxidation and aggregation process.The metal atom methodology has also been used to synthesize silver microsphere/polymer composites. With quadratic electrooptic phase modulation, these composites were found to show a third order susceptibility enhanced by coupling the dipolar surface plasmon mode of the particles with incident light.

A Novel Fluorinated Carbon Material for Primary Lithium Battery

2013 ◽  
Vol 331 ◽  
pp. 427-430 ◽  
Author(s):  
Jia Chun Lu ◽  
Zhi Chao Liu ◽  
Ping Huang ◽  
Quan Fang ◽  
Min Hua Zhu
Keyword(s):  
Cathode Materials ◽  
Electronic Conductivity ◽  
Energy Performance ◽  
High Energy ◽  
High Specific Surface Area ◽  
High Energy Density ◽  
Bamboo Charcoal ◽  
Stored Energy ◽  
Electrochemical Assay ◽  
Layer Spacing

Li/graphite fluoride (GFx) cells have been widely noticed during the past decades due to its highest theoretical capacity in primary lithium batteries, high energy density, long shelf life, safety and a wide operating temperature. However, the low electronic conductivity and discharge potential Li/GFx cells obviously limited its applications. In order to improve the energy performance of Li/GFx cells, an efficient method is to increase the transportation ability of Li+ in cathode. Considering its high specific surface area and large layer spacing, bamboo charcoal is suitable for preparing the cathode materials with highly stored energy. Here, we synthesized the fluorinated bamboo charcoal (FBC) as the novel cathode materials based on gas-solid fluorination. Electrochemical assay show that the lithium/fluorinated bamboo charcoal cells have a novel discharged voltage of 3V versus Li/Li+ electrode, and a special capacity above 750 mAh g-1. The lithium/fluorinated bamboo charcoal cells may be used for new highly stored energy device in the future.

IR Spectra and Discharge Performance of Fluorinated Bamboo Charcoals

2015 ◽  
Vol 723 ◽  
pp. 789-792
Author(s):  
Ping Huang ◽  
Jia Chun Lu ◽  
Sheng Bo Jiang ◽  
Zhi Chao Liu
Keyword(s):  
Ir Spectra ◽  
Specific Capacity ◽  
Target Material ◽  
High Energy ◽  
High Specific Surface Area ◽  
High Energy Density ◽  
Discharge Process ◽  
Bamboo Charcoal ◽  
Layer Spacing ◽  
Discharge Performance

Li/graphite fluoride (GFx) cells have been widely noticed during the past decades due to its highest theoretical capacity, high energy density, long shelf life, safety and a wide operating temperature range in primary lithium batteries. Bamboo charcoal is cheap and widely used carbon with high specific surface area and large layer spacing, which is suitable to be fluorinated to form carbon fluoride. Five products with varied fluorine and color were obtained by fluorinating bamboo charcoal under varied reaction conditions. FT-IR spectra of these FBCs were studied. The absorbance peak related to C-F band was involved into five Gaussian peaks, and the area of each peak was calculated. The specific discharge capacity of each product was measured by galvanostatic discharging at 0.01C rate. It is turned out that there is a positive linear relationship between the specific capacity and the percentage of the peak area related to semi-covalent covalent C-F, if the carbon in the products was removed. The discharge curves showed that the discharge process could be divided into three parts. The pure compound corresponding to the first part of the discharge is the target material we actually want.

scholarly journals Simulation of Si-MOSFETs with the Mutation Operator Monte Carlo Method

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 343-347 ◽  
Author(s):  
Jürgen Jakumeit ◽  
Amanda Duncan ◽  
Umberto Ravaioli ◽  
Karl Hess
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
High Energy ◽  
Stationary Condition ◽  
Good Resolution ◽  
Mutation Operator ◽  
Hot Electron ◽  
High Energy Tail ◽  
Electron Distributions ◽  
Dimensional Simulation

The Mutation Operator Monte Carlo method (MOMC) is a new type of Monte Carlo technique for the study of hot electron related effects in semiconductor devices. The MOMC calculates energy distributions of electrons by a physical mutation of the distribution towards a stationary condition. In this work we compare results of an one dimensional simulation of an 800nm Si-MOSFET with full band Monte Carlo calculations and measurement results. Starting from the potential distribution resulting from a drift diffusion simulation, the MOMC calculates electron distributions which are comparable to FBMC-results within minutes on a modern workstation. From these distributions, substrate and gate currents close to experimental results can be calculated. These results show that the MOMC is useful as a post-processor for the investigation of hot electron related problems in Si-MOSFETs. Beside the computational efficiency, a further advantage of the MOMC compared to standard MC techniques is the good resolution of the high energy tail of the distribution without the necessity of any statistical enhancement.

A New Primary Lithium Battery with Fluorinated Ketjenblack Cathode

2013 ◽  
Vol 704 ◽  
pp. 98-101 ◽  
Author(s):  
Jia Chun Lu ◽  
Zhi Chao Liu ◽  
Ping Huang ◽  
Quan Fang ◽  
Min Hua Zhu
Keyword(s):  
Lithium Batteries ◽  
Cathode Materials ◽  
Electronic Conductivity ◽  
Energy Performance ◽  
High Energy ◽  
High Energy Density ◽  
Stored Energy ◽  
Electrochemical Assay ◽  
Layer Spacing ◽  
Large Bulk

Li/graphite fluoride (GFx) cells, with highest theoretical capacity in primary lithium batteries, high energy density, long shelf life, safety and a wide operating temperature, have been widely noticed during the past decades. However, the low electronic conductivity and discharge potential of Li/GFx cells obviously limited its applications. The key to improve the energy performance of Li/GFx cells is to increase the transportation ability of Li+ in cathode materials. Considering its high specific surface area, large bulk volume and layer spacing, Ketjenblack is used for preparing the cathode materials with highly stored energy. Based on gas-solid fluorination, we synthesized the fluorinated Ketjenblack (FKB). As the cathode materials of lithium batteries, electrochemical assay show that the lithium/FKB cells have a novel discharged voltage of 3V versus Li/Li+ electrode, and a special capacity near 800 mAh g-1. The lithium/FKB cells may be used for a new highly stored energy device.

scholarly journals Influence of Electron-Electron Interaction on Electron Distributions in Short Si-MOSFETs Analysed Using the Local Iterative Monte Carlo Technique

VLSI Design ◽  
2001 ◽  
Vol 13 (1-4) ◽  
pp. 175-178
Author(s):  
T. Mietzner ◽  
J. Jakumeit ◽  
U. Ravaioli
Keyword(s):  
Monte Carlo ◽  
Electron Scattering ◽  
Electron Distribution ◽  
Field Effect Transistors ◽  
High Energy ◽  
Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
Electron Interaction ◽  
High Energy Tail ◽  
Electron Distributions

The effects of electron–electron interaction on the electron distribution in n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) are studied using the Local Iterative Monte Carlo (LIMO) technique. This work demonstrates that electron–electron scattering can be efficiently treated within this technique. The simulation results of a 90 nm Si-MOSFET are presented. We observe an increase of the high energy tail of the electron distribution at the transition from channel to drain.

scholarly journals Probing solar flare accelerated electron distributions with prospective X-ray polarimetry missions

2020 ◽  
Vol 642 ◽  
pp. A79
Author(s):  
Natasha L. S. Jeffrey ◽  
Pascal Saint-Hilaire ◽  
Eduard P. Kontar
Keyword(s):  
Solar Flare ◽  
Electron Distribution ◽  
Electron Acceleration ◽  
High Energy ◽  
Transport Processes ◽  
Spectral Measurements ◽  
X Ray ◽  
Electron Distributions ◽  
Energy Cutoff ◽  
Imaging Polarimetry

Solar flare electron acceleration is an extremely efficient process, but the method of acceleration is not well constrained. Two of the essential diagnostics, electron anisotropy (velocity angle to the guiding magnetic field) and the high energy cutoff (highest energy electrons produced by the acceleration conditions: mechanism, spatial extent, and time), are important quantities that can help to constrain electron acceleration at the Sun but both are poorly determined. Here, by using electron and X-ray transport simulations that account for both collisional and non-collisional transport processes, such as turbulent scattering and X-ray albedo, we show that X-ray polarization can be used to constrain the anisotropy of the accelerated electron distribution and the most energetic accelerated electrons together. Moreover, we show that prospective missions, for example CubeSat missions without imaging information, can be used alongside such simulations to determine these parameters. We conclude that a fuller understanding of flare acceleration processes will come from missions capable of both X-ray flux and polarization spectral measurements together. Although imaging polarimetry is highly desired, we demonstrate that spectro-polarimeters without imaging can also provide strong constraints on electron anisotropy and the high energy cutoff.

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