摘要:

The characteristics of a magnetic Ericsson refrigeration cycle are investigated on the basis of the thermodynamic properties of the ferromagnetic material. The effect of field‐dependent heat capacity on regeneration is discussed. The coefficients of performance of the Ericsson magnetic refrigeration cycle are derived. Finally it is pointed out that, according to theoretical analysis, the Ericsson magnetic refrigeration cycle can be expected to reach or approach perfect regeneration by using a mixture of several magnetic materials as the working substance.

ISSN:0021-8979    

DOI:10.1063/1.352158

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A Michelson interferometer and an optical beam deflection configuration (both shot noise and diffraction limited) are compared for application in an atomic force microscope. The comparison shows that the optical beam deflection method and the interferometer have essentially the same sensitivity. This remarkable result is explained by indicating the physical equivalence of both methods. Furthermore, various configurations using optical beam deflection are discussed. All the setups are capable of detecting the cantilever displacements with atomic resolution in a 10 kHz bandwidth.

ISSN:0021-8979    

DOI:10.1063/1.352149

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The energy distribution of fast atoms produced by modifying a McIlraith‐type fast atom beam (FAB) source is measured using a retarding‐field energy analyzer coupled with an ionization chamber. The energy distribution mainly depends on the gas pressure of the FAB source. When the gas pressure is low, the main energy distribution peak coincides with the discharge voltage, so the acceleration energy of the ions is retained when they become fast atoms. When the gas pressure is high, the peak energy appears at about 25% of the discharge voltage and has a broader spectrum. The energy distribution is almost completely independent of the discharge voltage, discharge current, and the geometry of the source anode. The fast atoms are mainly produced by resonant charge‐transfer collisions inside the source. These collisions are dominant over electron‐ion recombinations for FAB formation.

ISSN:0021-8979    

DOI:10.1063/1.352173

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The thermal stresses in double‐coated optical fibers at low temperature have been analyzed. The lateral pressure and normal stresses in the glass fiber, primary coating, and secondary coating have been derived. The thermal stresses in the optical fiber are affected by the temperature drop, material properties of the primary and secondary coatings, and their thickness. It is possible to select a suitably polymeric coating to produce minimum lateral pressure in the glass fiber. In order to minimize the thermally induced bending loss, it was found that if the thickness of the polymeric coatings increases, the Young’s modulus of primary coating should increase, but the Young’s modulus of the secondary coating should decrease.

ISSN:0021-8979    

DOI:10.1063/1.352336

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Nonlinear couplers composed of two different saturable nonlinear cores are examined. By combining one self‐focusing core appositely with another core of different nonlinearity, which can be self‐focusing, linear, or self‐defocusing, the detrimental effect of nonlinear saturation on the coupler formed is greatly reduced compared with that on the conventional coupler composed of two identical self‐focusing cores. This finding provides a way of relaxing the practical limitation to operational power of a saturable nonlinear coupler especially when high nonlinearity is involved for low‐power operation.

ISSN:0021-8979    

DOI:10.1063/1.352170

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In the present paper third order chromatic aberrations have been computed for an immersion lens and an einzel lens based on canonical aberration theory. The electron trajectories with up to third order chromatic aberrations have been compared with the real trajectories. They are in good agreement, and the computational errors are believed to be about 0.2%. Therefore, the canonical theory of higher order chromatic aberration has been verified. As a practical application, for a typical electrostatic lens, the first, third order chromatic aberrations and the third order geometric aberrations, which are functions of the object side beam half‐angle, have been presented in detail. It is expected that the results are useful for designing and optimizing a low chromatic aberration electrostatic lens.

ISSN:0021-8979    

DOI:10.1063/1.352133

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Electron cyclotron resonance (ECR) reactors are now being investigated for use in the plasma processing of semiconductors. The attractive feature of ECR excitation is that high plasma densities (1010–1012cm−3) can be obtained at low pressures (0.1–a few mTorr). In this paper, we present results from a computer simulation of the electron kinetics in ECR reactors. The model is a multidimensional Monte Carlo simulation coupled with a fluid simulation with which the electron energy distribution (EED) may be calculated. We find that the electron temperature (Te=2/3⟨&egr;⟩) in Ar plasmas (0.1–10 mTorr, 100s W) is 10–20 eV in the ECR zone, falling to a few to 5 eV downstream of the ECR zone, in general agreement with experiments. The EED can be described as being multitemperature with a low energy component (5–10 eV) and a high energy tail extending to many 10sto 100s eV. Predicted ambipolar potentials are 10–30 V, increasing with decreasing pressure and increasing power deposition.

ISSN:0021-8979    

DOI:10.1063/1.352144

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

To examine the mechanism of film deposition in a planar rf CH4discharge plasma, measurements were made of the spatial distributions of the deposition rate and optical emission intensity along the discharge axis between parallel electrodes. Optical‐absorption properties of the deposited carbon films were also measured over both the infrared and visible regions. To measure the spatial deposition rates, the substrate surface was elevated from the cathode electrode with the use of quartz glass plates. It was found that the spatial properties of films, which were deposited in both the ion‐sheath and bulk‐plasma regions, differ markedly from each other. The carbon films obtained from within the ion‐sheath region were found to be extremely hard, while those obtained in the bulk‐plasma region were polymerlike soft films. This disparity was thought to be due to the difference in the kinetic energy of the ions bombarding the substrate surface; that is, the substrate surface potential could be changed by elevating the substrate surface. These results were incorporated in the discussion of the deposition mechanism, with emphasis on the contribution of ion bombardment to the film‐deposition process. It was tentatively concluded that the film‐deposition rate was predominantly dependent on the product of the ion kinetic energy and ion flux density that reached the substrate surface.

ISSN:0021-8979    

DOI:10.1063/1.352145

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A free‐standing, extremely thin silicon membrane, prepared by chemical vapor deposition of an epitaxial layer and subsequent anisotropic, selective etching, has been studied. The epitaxial layer consisted of a sandwich structure of undoped and highly boron/germanium‐doped films, serving as an etch stop. The results of double‐ and triple‐crystal x‐ray diffractometry in the Bragg and Laue case, i.e., in reflection and transmission, respectively, are reported using x radiation between 8.05 (CuK&agr;1) and 17.5 keV (MoK&agr;1) photon energy. The thickness of the crystal was determined toz0=(30±1) &mgr;m and its curvature to <7×10−4m−1. The influence of the doped etch stop layer on the x‐ray reflectivity is discussed in detail.

ISSN:0021-8979    

DOI:10.1063/1.352146

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The effects of high‐dose silicon and arsenic ion implantation on the electrical and structural properties of silicon layers are investigated. Combining electrical, transmission electron microscopy, and triple‐crystal x‐ray‐diffraction measurements made it possible to characterize the effects of thermal annealing both on defect annihilation mechanisms and on electrical doping activation. It is clearly shown that a low‐temperature (≤450 °C) electrical activation process is taking place in the amorphous surface layer induced by high‐dose ion implantation. This phenomenon is found to be completely independent of the recrystallization regrowth by solid phase epitaxy which occurs at higher temperature. This electrical activation process is found to be well described by a local relaxation model involving point defect migration.

ISSN:0021-8979    

DOI:10.1063/1.352147

出版商:AIP    

年代:1992

数据来源: AIP