摘要:

The role of the equation of state (EOS) is reviewed as an analytical vehicle to express material pressure as a function of density and temperature (or internal energy in the case of adiabatic transition). Starting from the fundamental laws of thermodynamics, three criteria are developed to measure the stability of equations of state, and are applied specifically to the Mie–Gru¨neisen EOS, with Hugoniot reference, to investigate the stability characteristics thereof. This EOS is singled out for study because of its relative importance in the computational modeling of shock transition. Results indicate numerous possibilities of instability under various circumstances. Various remedies are proposed to correct the observed instabilities and compared with existing models.

ISSN:0021-8979    

DOI:10.1063/1.349406

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The reflection and transmission properties of finely divided fractal layers are investigated and characterized. The results for electromagnetic or optical waves normally incident upon generalized Cantor bar fractal multilayers are found for various fractal dimensions and stages of growth. A new exact self‐similar algorithm is described which makes use of the self‐similarity of the structures to clearly display the underlying physics. This fractal computational scheme provides the reflection and transmission coefficients for fractally distributed layers with extreme economy when compared to traditional approaches. Finally, a method for extracting fractal descriptors from scattered data is discussed. High‐ and low‐ frequency regimes are examined.

ISSN:0021-8979    

DOI:10.1063/1.349407

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The quantum‐well laser is described in terms of the appropriate quasi‐Fermi levels and Einstein coefficient for stimulated emission. Emission frequencies, thresholds currents temperature dependencies, and linewidths are determined as a function of the quantum‐well parameters, the photon lifetime, the temperature, and the emission coefficient. Correlation with existing data is demonstrated.  

ISSN:0021-8979    

DOI:10.1063/1.349408

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

LiNbO3thin‐film optical waveguides with high crystallinity and good surface morphology have been grown on 5 mol % MgO‐dopedZ‐plate LiNbO3substrates by liquid‐phase epitaxy using Li2O‐V2O5flux. A small lattice mismatch less than 4×10−3A˚ in theXaxis, a small linewidth of 11sin an x‐ray rocking curve, and a perfect mirror surface are realized by choosing a melt composition. Ordinary refractive indexnoat a wavelength of 0.6328 &mgr;m is unchanged (2.287) with melts of different compositions, but extraordinary refractive indexnecan be changed from 2.205 to 2.192 or less by increasing Li2O in the melt with V2O5fixed at 40 mol %. The optical absorption loss at a wavelength of 0.5145 &mgr;m caused by V incorporated from the flux is significantly reduced from 25 to 1.6 dB/cm by O3annealing for 1 h at 600 °C. Efficient second‐harmonic generation of TE0(1.064 &mgr;m) →TM0(0.532 &mgr;m) for a single‐poled film is observed by a temperature‐tuning method. The mechanism of self poling and domain inversion which were revealed by the present research is discussed.

ISSN:0021-8979    

DOI:10.1063/1.349409

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Electron flow in and into an applied‐B ion diode is calculated, including the effects of turbulence produced by streaming instabilities. A technique is developed for including these effects in a numerical simulation. The results of two‐dimensional simulations using this technique in the electromagnetic particle‐in‐cell codemagicare presented.

ISSN:0021-8979    

DOI:10.1063/1.349410

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Electron cyclotron resonance (ECR) plasma reactors are being developed for etching and deposition of thin films during integrated circuit fabrication. To control critical parameters such as the flux and energy distribution of ions impacting surfaces, it is necessary to understand how these parameters are influenced by physical construction, electromagnetic design, and chemical kinetics. In this work, we report detailed measurements of ion velocity distributions in both the source and reactor regions of an ECR system using mixtures of Ar and He. Using Doppler‐shifted laser‐induced fluorescence spectroscopy, we measure metastable Ar‐ion velocity distributions parallel and perpendicular to the magnetic field direction as a function of magnetic field amplitude, pressure, rf bias voltage, and microwave power. The measurements, in turn, are used to estimate the magnitude of electrostatic potentials and fields parallel and perpendicular to the magnetic field. Indicative of ion trapping, we find nearly isotropic ion velocity distributions when the source is operated as a magnetic mirror and the He partial pressure is low; higher He pressures tend to cool the parallel velocity distribution. Downstream, we consistently observe bimodal ion velocity distributions: the fast component, created in the source, follows magnetic flux lines into the reactor; the slow component, created mostly where the plasma expands from the source into the reaction chamber, is more isotropic. The relative amplitudes of these two components, the average ion energy, and the ion energy distribution are easily controlled by changing pressure and magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.350332

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In this paper we present investigations of two kinds of aperture effects on charged particles in the presence of a magnetic field. The first is an experimental study of the plasma potential profiles in front of an aperture. Plasma potential is measured with emissive probes. The interaction between the plasma and the solid wall of the aperture results in a nonuniform potential profile. Our experiments show that suitable aperture biasing can smooth the electric field in front of the aperture. The second is the transmission of electrons through a finite thickness aperture. The experimental results of the latter are compared to results of a single particle orbit model. It is shown that transmission measurements can be used to estimate the electron perpendicular energy in the magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.349387

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The production process for the formation of H−ions in a surface conversion source is sputtering of hydrogen atoms from the converter surface layers by incident positive ions, followed by electron attachment via resonant charge exchange with the converter surface. The sputtering process is in direct relation to the converter surface composition. New experimental data led us to identify two different classes of converters: metallic converters, like solid barium(binary) and adlayer converters, like cesium on tungsten (ternary). For a binary converter the hydrogen in the surface layers is directly sputtered by the incoming ions. Consequently, the negative ion yield scales with the hydrogen concentration in the surface layers. In the cesium/tungsten system (ternary) the hydrogen at the surface isbelievedtobesandwiched between the cesium adlayer and the tungsten surface. Hence, the negative ion yield scales with the sputter coefficient of hydrogen on adsorbed cesium. This is experimentally confirmed.

ISSN:0021-8979    

DOI:10.1063/1.349365

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The growing conditions and the basic electronic and interface properties of InP‐nitride‐metal structures formed by indirect plasma‐enhanced nitridation are reported. The deposited nitride layer PxNyClzis a NP polymer with a chemical composition close to P3N5but with weak inclusions of H atoms. These nitride films are deposited at temperatures as low as 220–250 °C with growing rates of 50 A˚/min and stabilized by a post annealing at 300 °C in a reducing gaseous atmosphere. The optimized composition corresponds toEg=5.5 eV, &egr;r=6.2,n=1.95, a room‐temperature resistivity &rgr;≳1013&OHgr; cm and a breakdown voltageEr≳5×107V cm−1. The capacitance‐voltage characteristics of Au‐NP‐InP diodes reveal that quasi‐flat band and strong depletion regimes are reached, i.e., that the Fermi level in InP is swept through the entire upper half part of the electronic gap. TheseC‐Vcharacteristics are hysteresis free, and this allows a meaningful calculation of the interface states densityNisand of their energy distributionDis(E). This interface states energy distributionDis(E) is in the 1011cm−2 eV−1range and is very similar in magnitude to the ones observed at the InP‐oxide or InP‐sulfide interfaces despite the large differences in the growing atmospheres. The thermal stability of the InP‐NP interface, as checked by inspection of theI‐VandC‐Vcurves, is good till 500 °C, this is at least 300 ° higher than with sulfides.

ISSN:0021-8979    

DOI:10.1063/1.349366

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In this paper, we report the successful observation of the hybrid multiple diffraction (hybrid MD) in Renninger scans (RS) [M. Renninger, Z. Kristallogr.106, 141 (1937)]. These diffractions occur when the beam first diffracted by an inclined layer (or substrate) plane with respect to the sample surface crosses the interface layer/substrate to be rescattered by another substrate (or layer) plane towards the detector. The construction of an incidence diagram allows to establish the occurrence of the hybrid MD for heteroepitaxial layers. The layer imperfection (mosaic spread) is used to explain these extra features in RS together along the normal MD features. The case of a GaAs layer grown on a Si substrate is investigated.

ISSN:0021-8979    

DOI:10.1063/1.349367

出版商:AIP    

年代:1991

数据来源: AIP