摘要:

Manganese can be substituted in iron garnet films in order to increase the magnetostriction constants. When these films are grown under compression, magnetic anisotropy is introduced. The influence of manganese on film‐growth conditions and magnetic properties has been studied. Phenomenological equations are derived to describe the properties of the manganese‐containing garnet films. These equations were successfully applied in a test case of tailoring the properties of garnet films.

ISSN:0021-8979    

DOI:10.1063/1.332179

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The dielectric constant and loss were measured at several frequencies and temperatures for red mercuric iodide. The equivalent circuits for the sample, before and after a direct bias has been applied for a long time, are discussed. Complex impedance and loss tangent plots versus frequency and temperature show a contact barrier formation after long time polarization. Results are discussed in terms of gamma radiation detector performance.

ISSN:0021-8979    

DOI:10.1063/1.332180

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The dielectric breakdown of polyethylene subjected to a highly divergent electric field has been studied. The samples were held at room temperature and an alternating field of frequency 50 Hz applied. When the material contained only residual gas it was possible to detect light emanating from the bulk of the polymer. It is proposed that this was an electroluminescence of the polyethylene resulting from the recombination of charge carriers injected at the electrode–polymer interface with the deep trapping centers in the polyethylene. The detection of this light required the use of a very sensitive photomultiplier coupled to an optical microscope. When the material contained a dissolved gas in equilibrium, the behavior of the solid was found to depend on the chemical reactivity of the gas and on its electron affinity. In particular, the influence of oxygen has been studied. A model is proposed which accounts for all the experimental results and which underlines the fundamental role played in the prebreakdown process by the gas dissolved in the polymer.

ISSN:0021-8979    

DOI:10.1063/1.332181

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The time dependence of polarization reversal in &bgr;‐phase polyvinylidene fluoride has been measured under a step‐function field up to 200 MV/m below room temperature. Fairly fast switching has been found to occur which might be accomplished by a 180° rotation of individual chains around their chain axes in the crystalline lamellae. The field dependence of the switching time is strong as indicated by a very high activation field of 1–2 GV/m or a large power law index of 8.0–10.5. The shape of switching transient has been investigated phenomenologically and by computer simulation on the basis of a nucleation and growth model. It is shown that the model is consistent with observations if one‐dimensional growth and an appropriate ratio of growth velocity to nucleation probability are assumed. Effects of the size of nuclei and domains are examined.

ISSN:0021-8979    

DOI:10.1063/1.332182

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The optical and elastic properties of AgTlSe have been measured, including acoustic velocities, optical transmission, refractive indices and birefringences. The relatively low shear velocities and high refractive index indicate that the acousto‐optic figure of merit of AgTlSe is large.

ISSN:0021-8979    

DOI:10.1063/1.332135

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A dichroic dye was added to smecticAliquid crystals as an absorber of laser energy to eliminate the need to conduct heat from an external absorber to the liquid crystal layer. It was found that the dichroic ratio of the added dye is an important factor in the recording mechanism of the liquid crystal. The resolution of the written image was improved by doping with a dye having a large dichroic ratio.

ISSN:0021-8979    

DOI:10.1063/1.332136

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

General considerations are applied to optimize the sensitivity of ellipsometric measurements for thin films on a substrate.s‐ orp‐wave suppression conditions are found to give maximum sensitivity. Approximate values of the optical parameters of the films and substrate are used to calculate discrete film thicknesses for thes‐ orp‐wave suppression to occur. For null fixed‐wavelength ellipsometry, these calculations are limited to experimentally available wavelengths, e.g., at strong emission lines from a Hg lamp. Films with thicknesses near the calculated ones are then deposited on the substrate. The ellipsometric parameters &psgr; and &Dgr; are obtained at multiple angles of incidence and wavelengths, and a least‐squares procedure is used for the analysis. The method has been applied to silicon nitride films on GaAs. The problem of correlation between the calculated optical parameters of the system is addressed. It is shown that the multiple‐wavelength analysis decreases significantly the correlations as compared to single‐wavelength analysis.

ISSN:0021-8979    

DOI:10.1063/1.332137

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Laser drilling in thin metal plates has been studied with three different types of laser rods: NdYAG (yttrium aluminum garnet, Y3Al5O12), NdYAP (ytrium ortho aluminate, YAlO3), and Nd glass. The rods have widely different pulse shapes and thus different drilling performance. Our experiments were made in 0.5‐mm plates of aluminum and stainless steel. The length of the laser pulse was 200 &mgr;s and the pulse energies were up to approximately 1 J. When small holes are drilled in some materials, e.g., aluminum, NdYAG gives holes completely clogged by molten material. The use of NdYAP solves these problems by a reduction in the amount of molten material and a more efficient ejection of the molten material produced. Nd glass is also usable, but higher energy is required. In materials without the clogging problem, NdYAG is the most efficient.

ISSN:0021-8979    

DOI:10.1063/1.332138

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The diffusion of beryllium and zinc into GaAs substrates during liquid phase epitaxial growth ofp‐Ga0.2Al0.8As layers was investigated. The diffusion coefficients were determined from the profile of free‐carrier concentration in thep‐GaAs region. Comparing the diffusion coefficients of Be and Zn, the diffusion coefficient of Be was found to be about ten times higher than that of Zn in the temperature range above 750 °C. For Be diffusion, if the surface free‐carrier concentration in thep‐GaAs layer is lower than about 6×1018cm−3, the diffusion can be expressed as diffusion from a semi‐infinite source and the free‐carrier concentration profiles are represented by the error function complements. With regard to temperature dependence, the diffusion coefficient takes the formD=D0 exp(−E0/kT), whereD0=0.66 cm2 s−1andE0=2.43 eV in the temperature range 700–900 °C. If the surface free‐carrier concentration was higher than about 6×1018cm−3, anomalous behavior was observed; i.e., the diffusion could be no longer represented by a constant diffusion coefficient.

ISSN:0021-8979    

DOI:10.1063/1.332139

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A model is presented for calculating the incorporation probability and steady state depth distribution of accelerated dopants in films deposited from the vapor phase. Terms accounting for thermal sticking probabilities, low‐energy implantation, diffusion, surface segregation, and preferential sputtering are included. Model predictions are shown to be in good agreement with Ota’s experimental data [J. Appl. Phys.51, 1102 (1980)] for the incorporation probability of As, as a function of film‐growth temperature and As acceleration energy, in Si films grown by molecular beam epitaxy.

ISSN:0021-8979    

DOI:10.1063/1.332140

出版商:AIP    

年代:1983

数据来源: AIP