摘要:

We review work on In2O3:Sn films prepared by reactivee‐beam evaporation of In2O3with up to 9 mol % SnO2onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4Torr. Optimized coatings have crystallite dimensions ≳50 nm and aC‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐&mgr;m range, byX‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4&OHgr; cm. The corresponding mobility is ∼30 cm2/V s. The complex dielectric function &egr; is reported.These data were obtained from carefully selected combinations of spectrophotometric transmittance and reflectance data. It is found that &egr; can be reconciled with the Drude theory only by assuming a strongly frequency‐dependent relaxation energy between the plasma energy and the band gap. We review a recently formulated quantitative theoretical model for the optical properties which explicitly includes the additive contributions to &egr; from valence electrons, free electrons, and phonons. The theory embodies an effective‐mass model forn‐doped semiconductors well above the Mott critical density. Because of the high doping, the Sn impurities are singly ionized and the associated electrons occupy the bottom of the conduction band in the form of an electron gas. The Sn ions behave approximately as point scatterers, which is consistent with pseudopotential arguments. Screening of the ions is described by the random phase approximation. This latter theory works well as a consequence of the small effective electron radii. Exchange and correlation in the electron gas are represented by the Hubbard and Singwi–Sjo¨lander schemes. Phonon effects are included by three empirically determined damped Lorentz oscillators. Free‐electron properties are found to govern the optical performance in the main spectral range. An analysis of the complex dynamic resistivity (directly related to &egr;) shows unambiguously that Sn ions are the most important scatterers, although grain‐boundary scattering can play some role in the midvisible range.As a result of this analysis one concludes that the optical properties of the best films approach the theoretical limit. Band‐gap shifts can be understood as the net result of two competing mechanisms: a widening due to the Burstein–Moss effect, and a narrowing due to electron‐electron and electron‐ion scattering. The transition width—including an Urbach tail—seems to be consistent with these notions. Window applications are treated theoretically from detailed computations of integrated luminous, solar, and thermal properties. It is found that In2O3:Sn films on glass can yield∼78% normal solar transmittance and ∼20% hemispherical thermal emittance. Substrate emission is found to be insignificant. Antireflection with evaporated MgF2or high‐rate sputtered aluminum oxyfluoride can give ∼95% normal luminous transmittance, ∼5% normal luminous reflectance, little perceived color and little increase in emittance. A color purity <1% in normal transmission and <10% in normal reflection is achievable for a daylight illuminant within extended ranges of film thickness.

ISSN:0021-8979    

DOI:10.1063/1.337534

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An analysis is made of a three‐mode 1200‐kg gravitational radiation detector operating at 1660 Hz and instrumented with a Clarke or IBM dc SQUID. The sensitivity projected for the detection of short pulses at 4.2 K and with optimum filtering is at the level ofdh∼10−18over a bandwidth of approximately 150 Hz.

ISSN:0021-8979    

DOI:10.1063/1.337549

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We develop a theory describing the propagation of an electromagnetic pulse propagating in one dimension through a medium of essentially arbitrary conductivity and polarizability. An integral solution for the pulse amplitude is obtained by means of the slowly varying envelope approximation. Within the limits of this approximation (which requires linear coupling of the pulse to the medium, smooth variation of the pulse envelope, and pulse widths large enough to contain many cycles of the pulse carrier frequency), our solution is quite general, and it allows relatively easy comparison of the evolution of various pulse shapes as they travel through the medium. We apply the theory to an analysis of a pulse propagating in a lossy plasma, and show that among pulses with similar initial widths and energies, the initial pulse shape can have significant effects on the subsequent pulse distortion, broadening, and energy transport. Specifically, for a lossy plasma, we find that the pulse energy transport is enhanced for pulses which are initially well localized about a central maximum.

ISSN:0021-8979    

DOI:10.1063/1.337550

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Calculations have shown that electrohydrodynamic instabilities can produce surface distortions that may locally enhance the electric field to the extent that field evaporation of ions can occur from a liquid metal surface. Linear analysis of the electrohydrodynamic equations of motion has yielded the regions of instability as well as the wavelengths and growth times of the dominant unstable mode as a function of applied electric field. In the calculation presented here, the liquid surface is followed well into the nonlinear regime using a surface integral method. The results agree with the linear theory where appropriate, and add further support to the feasibility of a large‐area liquid‐lithium ion source for inertial confinement fusion experiments on a light ion‐beam driver.

ISSN:0021-8979    

DOI:10.1063/1.337551

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Methods and approximations underlying the calculation of currents and spot sizes in rotationally symmetric triode electron guns are described. In the beam‐forming region, the Poisson equation is solved self‐consistently taking into account the initial velocities of the electrons (Langmuir’s law instead of Child’s law). In the remainder of the gun the space‐charge force is calculated directly from the solution of the Laplace equation and the position of the trajectories in the beam, which avoids the time‐consuming iterative solution of the Poisson equation. The space‐charge density and spot profiles are calculated with a fitting technique. The results of the simulation are compared with experimental values obtained for a gun similar to the guns used in modern display tubes. The currents agree within 5% over a range from 0.1 to 4 mA. The 5% intensity spot sizes were measured as a function of the focusing potential and they agree with the calculated spot size within 10%. At the lowest focusing potentials, for which the spot is focused too strongly, the discrepancies are somewhat larger. The spot profiles give a fairly accurate impression of the haze surrounding the spot and the optimum focusing potentials agree within 50 V.

ISSN:0021-8979    

DOI:10.1063/1.337552

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An extensive range of solid solubility was found in the LiNb3O8‐TiO2system. The solid‐solution phase has the undistorted rutile structure for 0.40≤x≤1.0 in (Li0.25Nb0.75O2)1−x(TiO2)x. A member of this series, withx≊0.58, is proposed to be the intermediate phase formed during Ti indiffusion in LiNbO3during optical waveguide formation, rather than Ti0.65Nb0.35O2as was previously postulated. This assignment agrees with the experimental results of previous studies of Ti indiffusion into LiNbO3single crystals, and is consistent with a Ti diffusion mechanism based on defect chemistry studies. The preparation and structural characterization of the LiNb3O8‐TiO2solid‐solution phase is discussed.

ISSN:0021-8979    

DOI:10.1063/1.337777

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Planar CH targets were irradiated by 400‐ps and 1‐ns pulses of 0.27‐&mgr;m light at intensities of 5×1012–1014W/cm2. The mass ablation rate obtained from time integrated x‐ray line emission from layered targets was found to bem˙=1.5×105(Ia/1013W/cm2)0.5g/cm2s. Using this result and the ion blowoff velocity, the ablation pressure scaled asPa=3.9 (Ia/1013W/cm2)0.6Mbar. Comparisons to similar experiments at 0.53 &mgr;m indicate that the mass ablation rate and pressure scale with laser wavelength as &lgr;−1.4and &lgr;−0.9, respectively. The intensity and wavelength scalings are found to agree with analytic predictions for spherical geometry rather than planar models. Comparisons are also made with previously reported measurements at other wavelengths and geometries.

ISSN:0021-8979    

DOI:10.1063/1.337553

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The irradiation of a KrF laser (248 nm) into the interelectrode space affects the electric flashover characteristics there. The results obtained show that negative oxygen ions dominate formation of the interelectrode arc in air. A laser beam is introduced parallel to the interelectrode axis and the equipment is arranged to prevent the occurrence of photoelectric effects on the electrode surfaces. The time separation between laser firing and application of the interelectrode voltage is varied from 10 ns to 10 ms. The interelectrode spacing is set in the range 2–12 cm. The arc formation time and the flashover probability are measured. The initial ion number density is estimated experimentally to be on the order of 1011cm−3throughout the channel.

ISSN:0021-8979    

DOI:10.1063/1.337554

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Atom arrangements in III‐V ternary alloy semiconductors are discussed using a thermodynamic analysis in which the elastic strain caused by mixing is considered as the mixing enthalpy. In calculating the strain energy, both bond‐stretching and bond‐angle distortion are taken into account, and Martin’s microscopic elastic constants are used. The results show that there is a preference for ordering but not for clustering in III‐V ternary alloy semiconductors. Values of short‐range order parameters which represent the degree of ordering are obtained for several alloy semiconductors.

ISSN:0021-8979    

DOI:10.1063/1.337555

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Very fine fibers of 3,4,9,10‐perylenetetracarboxylicdianhydride heated above 520 °C in argon (Ar) or argon/hydrogen (Ar/H2) gas were grown on pressed pellets. The fibers synthesized in Ar had a rectangular cross section of about 0.1–0.4 &mgr;m on a side with lengths up to 10 mm. By contrast, the fibers synthesized in Ar/H2had a flat‐ribbon like morphology with dimensions of 0.1–0.2 &mgr;m on one side and 0.4–2.0 &mgr;m on the side. Transmission electron microscopy revealed that component molecules roughly stacked parallel to the fiber axis. Infrared spectra of the fibers synthesized at around 520–550 °C exhibited aromatic C–H and C&squflg;C absorptions. The IR and laser–Raman spectra of the fibers can reasonably be explained by theoretically estimated vibrational modes of a poly‐peri‐naphthalene (PPN) structure. From these results together with elemental analysis data, we conclude that the fibers essentially consist of PPN molecules.

ISSN:0021-8979    

DOI:10.1063/1.337556

出版商:AIP    

年代:1986

数据来源: AIP