摘要:

The third‐order optical nonlinear susceptibilities of single‐crystalline and spin‐coated amorphous 4‐butoxy‐carbonyl‐methyl‐urethane polydiacetylene (red form) thin films were measured by third‐harmonic generation. The third‐harmonic intensities were calculated as a function of incident angle by solving the propagation equation of the electromagnetic field for a two‐layer system with one nonlinear media. From the best fit of the calculated and experimental data, the ( &khgr;(3)) values of the spin‐coated amorphous film (&khgr;(3)p) were found to be (9.6±1.0)×10−12esu and (2.0±0.2)×10−11esu at 1.064 and 1.319 &mgr;m, respectively, while the &khgr;(3)values of the crystalline ( &khgr;(3)pc) were (4.9±0.5)×10−11esu and (1.0±0.07)×10−10esu at 1.064 and 1.319 &mgr;m, respectively. A factor of five increase in the &khgr;(3)of the crystalline film is attributed to the orientation effect of the polymer chains. The enhancement of the nonlinearity at 1.319 &mgr;m may be due to either three‐photon or two‐photon resonant effects.

ISSN:0021-8979    

DOI:10.1063/1.344552

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Boron doping of silicon using a pulsed ArF excimer laser (&lgr;=193 nm, FWHM=17 ns) with B2H6has been investigated. Doping atoms are supplied mainly from both thermal and photochemical decomposition of the adsorbed layers on the surface. UV laser irradiation realizes both high surface carrier concentration (1×1021cm−3) and a very shallow junction (0.1 &mgr;m). Diodes fabricated by laser doping show good electrical characteristics (nfactor=1.10, reverse current density=1×10−7A/cm2at −5 V). Thermal annealing improves the reverse current density (3×10−9A/cm2at −5 V). A numerical calculation of boron concentration profiles has been performed by solving the diffusion equation in the melted region, which is evaluated by the heat conduction equation. From this calculation the diffusion coefficient of boron in liquid phase silicon (3×10−4cm2/s) is obtained.

ISSN:0021-8979    

DOI:10.1063/1.344553

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Si(100) wafers were implanted with O+at an energy of 180 keV to a dose of 2.3×1018/cm2in the separation by implanted oxygen process. Following implantation, one wafer was annealed at 1275 °C for 2 h. Spectroscopic ellipsometry measurements were then performed on these samples. Effective medium modeling of the measurements was used to nondestructively depth profile the samples. These results show that the superficial Si layer for the unannealed sample includes noncrystalline and crystalline components. In addition, the optical properties of the buried oxide for the unannealed sample were found to be different from those of bulk fused silica or thermal oxides of Si. The superficial Si layer for the annealed sample was crystalline Si, but the buried oxide consisted of a phase‐separated mixture of noncrystalline SiO2and crystalline Si. These results were further substantiated by selective chemical etch‐back studies and additional spectroscopic ellipsometry measurements, and by other techniques, including Raman spectroscopy, infrared transmission measurements, sputter depth profiling using x‐ray photoelectron spectroscopy, and Nomarski microscopy.

ISSN:0021-8979    

DOI:10.1063/1.344554

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Three‐point upper and lower bounds on the effective thermal expansion coefficient and specific heats of statistically isotropic suspensions of mutually impenetrable spheres are computed for the first time. The three‐point bounds depend upon the microstructure via a three‐point spatial correlation function of the medium. Both equisized and multisized spheres are considered, and hence the effect of polydispersivity in sphere size on the thermoelastic properties is determined. For reasons of mathematical analogy, the results of this study for the thermal expansion coefficient translate immediately into equivalent results for the hygroscopic expansion coefficient.

ISSN:0021-8979    

DOI:10.1063/1.344555

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A model for freely propagating transient electrical discharges, such as lightning and punch‐through arcs, is developed in this paper. We describe the electromagnetic fields by Maxwell’s equations and we represent the interaction of electric fields with the medium to produce current by ∂J/∂t=&ohgr;2(E−E*Jˆ)/4&pgr;, where &ohgr; andE* are parameters characteristic of the medium,J≡current density, andJˆ≡J/‖J‖. We illustrate the properties of this model for small‐diameter, guided, cylindrically symmetric discharges. Analytic, numerical, and approximate solutions are given for special cases. The model describes, in a new and comprehensive fashion, certain macroscopic discharge properties, such as threshold behavior, quenching and reignition, path tortuosity, discharge termination with nonzero charge density remaining along the discharge path, and other experimentally observed discharge phenomena. Fields, current densities, and charge densities are quantitatively determined from given boundary and initial conditions. We suggest that many macroscopic discharge properties are properly explained by the model as electromagnetic phenomena, and we discuss extensions of the model to include chemistry, principally ionization and recombination.

ISSN:0021-8979    

DOI:10.1063/1.344556

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Metastable atoms emitted from the anode of a hot‐cathode low‐voltage Ar gas discharge produce two peaks in the time‐of‐flight distribution. The slow peak typifies atoms with a thermal velocity distribution in the discharge. The fast peak can be approximated by a Gaussian function, and its dependence on the discharge current, voltage, and pressure is presented. The origin of the fast peak is investigated experimentally and shown to represent fast Ar(3P2,0) from the discharge.

ISSN:0021-8979    

DOI:10.1063/1.344557

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The influence of a radial electron density inhomogeneity on plasma modes propagating in a cylindrical bounded plasma immersed in an axial static magnetic field, and the variations of the wave characteristics induced by a dielectric layer surrounding the plasma have been studied. The computations show that the electromagnetic‐field radial distribution can be very sensitive to the electron density gradient, with or without the presence of the dielectric.

ISSN:0021-8979    

DOI:10.1063/1.344558

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The Balmer &bgr; and &ggr; line shapes have been analyzed to determine the relative density and the temperature of hydrogen atoms in magnetic multicusp plasma generators. Results for a 90‐V, 4–40‐mTorr, 1–18‐A conventional multicusp plasma generator and a 50‐V, 4‐mTorr, 1–15‐A hybrid multicusp plasma generator are presented. The relative number density of hydrogen atoms increased smoothly with pressure and discharge current but never exceeded 10%. The absolute atomic number density in a 90‐V 10‐A discharge varied in proportion with pressure. The atomic temperature (in the 0.1–0.4‐eV range) decreased with pressure and slowly increased with the discharge current. The role of atoms in the processes determining the H−temperature and the H2vibrational and rotational temperatures is discussed. The results confirm that in multicusp negative‐ion sources collisional excitation of ground state atoms and molecules by energetic electrons is the dominant process in Balmer‐&bgr; and ‐&ggr; light emission.

ISSN:0021-8979    

DOI:10.1063/1.344559

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Copper diffusion in mercuric iodide was studied by low‐temperature photoluminescence (PL) spectroscopy and Auger electron spectroscopy. A broad radiative emission band at a wavelength of about 6720 A˚ in the PL spectra was found to be related to Cu incorporation in the crystal. PL spectra obtained from surface doping experiments indicate that Cu is a rapid diffuser in HgI2bulk material. Auger electron spectroscopy performed as a function of depth from the crystal surface confirms the rapid bulk diffusion process of Cu in HgI2. Fabrication of HgI2nuclear detectors with Cu electrodes indicates that Cu is not acceptable as an electrode material, which is consistent with the fact that it diffuses easily into the bulk crystal and introduces new radiative recombination centers.

ISSN:0021-8979    

DOI:10.1063/1.344560

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Diffusion and interdiffusion in GaAs and GaAs/AlGaAs superlattices are shown to be consistent with the charged point‐defect model. The charged Ga vacanciesV3−Gaand interstitialsI2+Gaappear to control group II, III, and probably V element diffusion. After adjustment for carrier concentration and As pressure, these elements are found to have a nearly identical intrinsic diffusivity and activation energy over a wide range of temperature. A natural consequence of Ga diffusion via negative or positive point defects is that enhanced group‐III interdiffusion is expected with eithern‐ orp‐type doping. Anomalous enhancements in group‐II dopant diffusivity have been related to the supersaturation of Ga interstitials.

ISSN:0021-8979    

DOI:10.1063/1.344561

出版商:AIP    

年代:1990

数据来源: AIP