DENSITY-OF-STATES OF THE 2-DIMENSIONAL ELECTRON-GAS STUDIED BY MAGNETOCAPACITANCES OF BIASED DOUBLE-BARRIER STRUCTURES

The magnetocapacitive response of a double-barrier structure (DBS), biased beyond resonances, has been employed to determine the density of states (DOS) of the two-dimensional electron gas residing in the accumulation layer on the incident side of the DBS. An adequate procedure is developed to compare the model calculation of the magnetocapacitance with the experimental C vs B curves measured at different temperatures and biases. The results show that the fitting is not only self-consistent but also remarkably good even in well-defined quantum Hall regimes. As a result, information about the DOS in strong magnetic fields could reliably be extracted.

PHOTOLUMINESCENCE STUDIES ON VERY HIGH-DENSITY 2-DIMENSIONAL ELECTRON GASES IN PSEUDOMORPHIC MODULATION-DOPED QUANTUM-WELLS

We present photoluminescence studies on highly dense two-dimensional electron gases in selectively Si delta-doped GaAs/In0.18Ga0.82As/Al0.25Ga0.75As quantum wells (N(s) = 4.24 x 10(12) cm-2). Five well-resolved photoluminescence lines centered at 1.4194, 1.4506, 1.4609, 1.4695 and 1.4808 eV were observed, which are attributed to the subband excition emission. The subband separations clearly exhibit the feature of a typical quantum well with triangle and square potential. These very intensive and sharp luminescence peaks with linewidths of 2.2 to 3.5 meV indicate the high quality of the structures. Their dependence on the excitation intensity and temperatures are also discussed.

Fermi-Level Pinning at Metal/High-k Interface Influenced by Electron State Density of Metal Gate

The Fermi-level pinning (FLP) at the metal/high-k interface and its dependence on the electron state density of the metal gate are investigated. It is found that the FLP is largely determined by the distortion of the vacuum level of the metal which is quantitatively ruled by the electron state density of the metal. The physical origin of the vacuum level distortion of the metal is attributed to an image charge of the interface charge in the metal. Such results indicate that the effective work function of the metal/high-k stack is also governed by the electron state density of the metal.

Electron affinities and ionization potentials of 4d and 5d transition metal atoms by CCSD(T), MP2 and density functional theory

The electron affinities and ionization potentials of 4d and 5d transition metal atoms were studied by CCSD(T), MP2 and density functional methods. The calculated results indicate that density functional method B3LYP has the best overall performance in predicting both electron affinity and ionization potential. SVWN gives largest IP and EA for 4d and 5d atoms. For the two basis sets used in this study, LANL2DZ and SDD, the performance of B3LYP/SDD combination is better than B3LYP/LANL2DZ, in particular for electron affinity calculation.

Two-dimensional simulation of an electron cyclotron resonance plasma source with self-consistent power deposition

Using a refined two-dimensional hybrid-model with self-consistent microwave absorption, we have investigated the change of plasma parameters such as plasma density and ionization rate with the operating conditions. The dependence of the ion current density and ion energy and angle distribution function at the substrate surface vs. the radial position, pressure and microwave power were discussed. Results of our simulation can be compared qualitatively with many experimental measurements.

Shock Tube Studies on Recombination Kinetics of Sodium Ion with Electron

The ionization kinetics of sodium diluted in argon is studied in a shock tube, in which the test gas mixture is ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave. A Langmuir electrostatic probe is used to monitor the variation of the ion number density at the reflection shock wave region. The working state of the probe is in the near fi-ee fall region and a correction for reduction of the probe current due to elastic scattering in the probe sheath is introduced. At the temperature range of 800 to 2600 K and in the ambience of argon gas, the three-body recombination rate coefficient of the sodium ion with electron is determined: 3.43 x 10(-14)T(-3.77) cm(6).s(-1).

Shock Tube Studies on the Nonequlibrium Electron Affinity Kinetics of Fluorine Atom at High Temperatures

To study electron affinity kinetics, a shock tube method was applied, in which the test gas was ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave. As the quenching speed of 106 K/s was reached, a nonequilibrium ionization-recombination process occurred, which was dominated by ion recombination with electrons. A Langmuir electrostatic probe was used to monitor variation in the ion number density at the reflection shock region. The working state of the probe was analyzed...

(Ti,Al)N Film On Normalized T8 Carbon Tool Steel Prepared By Pulsed High Energy Density Plasma Technique

Under optimized operating parameters, a hard and wear resistant ( Ti,Al)N film is prepared on a normalized T8 carbon tool steel substrate by using pulsed high energy density plasma technique. Microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Hardness profile and tribological properties of the film are tested with nano-indenter and ring-on-ring wear tester, respectively. The tested results show that the microstructure of the film is dense and uniform and is mainly composed of ( Ti,Al)N and AlN hard phases. A wide transition interface exists between the film and the normalized T8 carbon tool steel substrate. Thickness of the film is about 1000 nm and mean hardness value of the film is about 26GPa. Under dry sliding wear test conditions, relative wear resistance of the ( Ti,Al)N film is approximately 9 times higher than that of the hardened T8 carbon tool steel reference sample. Meanwhile, the ( Ti,Al)N film has low and stable friction coefficient compared with the hardened T8 carbon tool steel reference sample.

Thickness And Component Distributions Of Yttrium-Titanium Alloy Films In Electron-Beam Physical Vapor Deposition

Thickness and component distributions of large-area thin films are an issue of international concern in the field of material processing. The present work employs experiments and direct simulation Monte Carlo (DSMC) method to investigate three-dimensional low-density, non-equilibrium jets of yttrium and titanium vapor atoms in an electron-beams physical vapor deposition (EBPVD) system furnished with two or three electron-beams, and obtains their deposition thickness and component distributions onto 4-inch and 6-inch mono-crystal silicon wafers. The DSMC results are found in excellent agreement with our measurements, such as evaporation rates of yttrium and titanium measured in-situ by quartz crystal resonators, deposited film thickness distribution measured by Rutherford backscattering spectrometer (RBS) and surface profilometer and deposited film molar ratio distribution measured by RBS and inductively coupled plasma atomic emission spectrometer (ICP-AES). This can be taken as an indication that a combination of DSMC method with elaborate measurements may be satisfactory for predicting and designing accurately the transport process of EBPVD at the atomic level.

The effects of coil current distribution in a cylindrical electron-cyclotron-resonance reactor

Using a 2-D hybrid model, the authors have found that external currents play an important role in the plasma parameters in the reactor. The plasma density, temperature and electrostatic potential would be significantly influenced by the applied external currents.

Behavior of ar plasma formed in a high-density plasma source - an ecr reactor

In order to develop the ultra-large scale integration(ULSI), low pressure and high density plasma apparatus are required for etching and deposit of thin films. To understand critical parameters such as the pressure, temperature, electrostatic potential and energy distribution of ions impacting on the wafer, it is necessary to understand how these parameters are influenced by the power input and neutral gas pressure. In the present work, a 2-D hybrid electron fluid-particle ion model has been developed to simulate one of the high density plasma sources-an Electron Cyclotron Resonance (ECR) plasma system with various pressures and power inputs in a non-uniform magnetic field. By means of numerical simulation, the energy distributions of argon ion impacting on the wafer are obtained and the plasma density, electron temperature and plasma electrostatic potential are plotted in 3-D. It is concluded that the plasma density depends mainly on both the power input and neutral gas pressure. However, the plasma potential and electron temperature can hardly be affected by the power input, they seem to be primarily dependent on the neutral gas pressure. The comparison shows that the simulation results are qualitatively in good agreement with the experiment measurements.