摘要:

A theoretical procedure is derived for the determination of the internal and external electromagnetic fields for a monochromatic beam incident upon a homogeneous particle of arbitrarily‐defined shape. The procedure is best suited for the analysis of near‐spherical particles (i.e., particles which deviate from a sphere by plus or minus a few tenths of a radii). Verification and demonstration calculations are presented. Also presented are calculations investigating the effect of a surface deformation on resonance excitation within an otherwise spherical particle.

ISSN:0021-8979    

DOI:10.1063/1.347493

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The electromagnetic field generated by a horizontal electric dipole in the air over the surface of a two‐layered region is determined for continuous‐wave excitation. The region of interest consists of a conductor coated with an electrically thin layer of dielectric under a half‐space of air. Simple explicit formulas are derived for the field at all points in all three regions, including the surface wave. Typical applications are to microstrip circuits and antennas and to remote sensing from the arctic ice.

ISSN:0021-8979    

DOI:10.1063/1.347494

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An experimental study of etching mechanisms in Cl2reactive ion etching is reported. The ion‐impact energy distribution and ion current density have been measuredinsituat the rf electrode of a parallel‐plate reactive ion etcher. This diagnostic method has been used for the first time to unravel etch characteristics in a practical etching environment. Samples of Si, SiO2, Ti, and TiSi2have been etched both in Cl2and Ar discharges, and the etch rates have been related to the ion flux and impact energy distribution. The angular impact energy distribution for both ions and neutrals has been calculated numerically in order to study the contribution of fast neutrals and the angular distribution of impinging species to the etch rate. Sputter yields have been determined from the observed etch rate and the ion current density, taking into account the (angular) energy distributions of bombarding ions and neutrals. Comparison of the obtained sputter yields in Ar and Cl2discharges with corresponding data from (chemically assisted) ion‐beam sputtering gives further insight into the etching mechanisms of Si, SiO2, Ti, and TiSi2.

ISSN:0021-8979    

DOI:10.1063/1.347495

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The effects of pump polarization on the performance of cw dye lasers have been investigated. A recently developed semiclassical model for synchronously pumped mode‐locked dye lasers is adapted to the problem of cw dye‐laser oscillation, and analytic expressions are obtained for the relationship between the pump power, pump polarization, and dye‐laser output power. The theoretical results are compared with experimental data obtained using an argon‐laser‐pumped rhodamine 6G dye laser.

ISSN:0021-8979    

DOI:10.1063/1.347496

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A new linear epoxy polymer containing 4‐amino‐4’‐nitrotolane chromophores attached to the chain backbone was synthesized in an attempt to enhance both the poling‐induced nonlinear optical susceptibility and its long‐term stability. The polymer films poled by corona discharge showed very large nonlinear optical doubling coefficients ofd33&bartil; 89 pm/V andd31&bartil;25 pm/V for incident light of 1.06 &mgr;m wavelength, and a linear electro‐optic coefficientr13&bartil;8 pm/V at 633 nm wavelength. Poling‐induced alignment of the nonlinear optical moieties showed no detectable decay in two weeks at ambient temperature, as studied by the birefringence. Even at 100 °C the relaxation time estimated from the birefringence decay was ca. 450 h, consistent with roughly 16% decrease indijcoefficients in 20 h at this temperature and also the extrapolation from the dielectric &agr; relaxation characteristics. The dielectric &agr; relaxation temperatures of the poled polymer samples exhibited higher values than that of the unpoled counterpart. This unusual behavior may be due to a significant contribution of Maier–Saupe thermotropic interactions among the tolane moieties that favor parallel alignment.

ISSN:0021-8979    

DOI:10.1063/1.347497

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The excitation of ultrasonic Lamb waves by an interdigital transducer (IDT) deposited on a piezoelectric plate is analyzed using the Green’s‐function method. The amplitudes of the generated Lamb waves are obtained in terms of the charge density on transducer electrodes. An electrostatic analysis that neglects piezoelectric coupling is used to relate this charge density to the voltage applied across the IDT. This is then used to calculate the radiation conductance of the transducer. Experimentally measured characteristics of interdigital transducers deposited on 128°Y‐XandY‐Zlithium niobate plates are found to be in fair agreement with theoretical calculations. The analysis can also be used to calculate the electromechanical coupling between the IDT and various Lamb‐wave modes. It is found that when the plate is more than a few acoustic wavelengths thick, the lowest‐order symmetric and antisymmetric Lamb modes are almost equally generated. The slight difference in the velocities of these modes gives rise to the beating effect, whereby energy launched by the IDT on one surface transfers periodically back and forth between the two surfaces as a sinusoidal function of the distance traveled. A 65‐MHz Lamb‐wave delay line fabricated on a 0.25‐mm‐thickY‐Zlithium niobate plate shows the beating effect, with a beat wavelength of 14.7 mm, in good agreement with theoretical calculations.

ISSN:0021-8979    

DOI:10.1063/1.347498

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The thermal dissociation of PH3and NH3injected through a Ta‐based high‐pressure gas‐injection cell were studied. Using a quadrupole mass spectrometer, the Ta was found to effectively dissociate the PH3into primarily P2, P4, and H2molecules with an injector temperature as low as 550 °C. The introduction of NH3through this same injector resulted in dissociation into N2and H2for an injector temperature greater than 900 °C. When NH3and PH3were coinjected, again P2, P4, N2, and H2were the primary molecules produced; however, an additional dimer, PN, was also detected. The PN concentration was maximum at a cell temperature of 700 °C. This dimer was found to be an effective source for introducing nitrogen as an isoelectronic trap in GaP.

ISSN:0021-8979    

DOI:10.1063/1.347447

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The heat phenomena including heating, melting, evaporation, cooling, and solidification are analyzed by means of mathematical modeling. Velocities and positions of phase boundaries (both evaporation and melting) are determined for different conditions of pulse‐periodic energy flow irradiation of metallic materials. Heat process dynamics, determined by the shape of the single energy pulse, by the energy input per oscillation period, and by the average energy density flow, are discussed.

ISSN:0021-8979    

DOI:10.1063/1.347448

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In previous studies it was reported that GaAs samples which were rapid thermal annealed exhibit bright bands adjacent to the surfaces in cathodoluminescence images of the cross sections. It is possible that the presence and depth of these bright bands are related to thermal stresses in the GaAs resulting from thermal gradients during heating and cooling. To investigate this possibility, a one‐dimensional mathematical model was developed to predict the temperatures through the thickness of the GaAs. Calculations of the thermal stress field show that the thermal stresses do not correlate with the depth of the bright bands.

ISSN:0021-8979    

DOI:10.1063/1.347449

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In this paper, we demonstrated the usefulness of low energy photoelectron spectrometer (LEPS) to characterize lubrication states on sputter carbon coated thin‐film disk. The threshold of photoelectric emission from lubricated sputter carbon, which was obtained by LEPS, gave significant information of the surface state on lubricated sputter carbon, and it explained the experimental results on the tribological behavior between the slider and lubricated disk. Furthermore, the thickness of the lubricant above 5 nm can be evaluated by measuring the attenuation of photoelectrons. It is applicable to theinsitumeasurement of photoelectric surface states of disk samples in ambient atmosphere without destroying them. This has a great advantage over the conventional photochemical analysis such as x‐ray photoelectron spectroscopy and Auger electron spectroscopy.

ISSN:0021-8979    

DOI:10.1063/1.347450

出版商:AIP    

年代:1991

数据来源: AIP