摘要:

Scanning capacitance microscopy is a new mechanically scanned microscopy. In its present configuration, the microscope has a demonstrated capability of detecting variations in surface topography of the order of 0.3 nm over areas of the order of 0.5 &mgr;m2. This great sensitivity to height changes is achieved by the placement of a capacitance probe some 20 nm above the sample surface. This paper describes the construction of the microscope and discusses its use in relating surface roughness of plastic parts to mold finish and material property variations.

ISSN:0021-8979    

DOI:10.1063/1.334506

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Flash bremsstrahlung with peak energy below 0.5 MeV can be obtained from multi‐MeV electron beams by Compton backscatter from a material with low photoelectric absorption. The efficiency is low but interesting, about 30 krad per megajoule electron beam energy, irrespective of electron voltage from 3 to 10 MeV.

ISSN:0021-8979    

DOI:10.1063/1.334507

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An irregular continuous conducting channel, linkage, or chain is formed in a sedimentary rock. The grain boundary of a polycrystalline and the blood vessel in a biological body shape such channels. In a previous paper we researched the effective conductivities of regular channeling textures by the finite element method (FEM) as a first approach to the problem of random channeling textures. In this paper we form irregular channeling patterns by computer simulation. The models are formed by randomly packing insulator squares into a metal sheet without any contact and overlap. We compute, by the FEM, the effective conductivities and compare them with previous results. It makes clear that the models are less conductive than a composite with a regular conducting channel. The conductivities agree well with the results from the granular effective medium approximation and from the extended Watson–Leath equation except when the metallic volume fraction is small.

ISSN:0021-8979    

DOI:10.1063/1.334508

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The components of the lateral‐wave field generated by vertical and horizontal antennas near the plane interface between air and earth (soil, water, etc.) are determined at points near the surface in air and at all points in the earth. This is the field incident on and scattered from inhomogeneities and objects in the earth.

ISSN:0021-8979    

DOI:10.1063/1.334509

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The electric field on the surface of the earth in an area above a buried insulated conductor is determined when the active source is a horizontal dipole also on the surface of the earth at some distance away. This is accomplished by first evaluating the current induced in the wire by the lateral‐wave field incident from the transmitter and then calculating the reradiated field just above the surface. Two orientations are considered. The field at the center of the buried conductor is (1) parallel toE1&rgr;(&rgr;,0,z) and (2) parallel toE1&fgr;(&rgr;,&pgr;/2,z). In an area above the conductor, the incident, scattered and total fields are evaluated for the conditions of a laboratory model. It is concluded that the method is potentially useful for locating buried or submerged regions with significantly different wave numbers from that of the surrounding earth.

ISSN:0021-8979    

DOI:10.1063/1.334510

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Applied‐B ion diodes are used in inertial confinement fusion research to generate multiterrawatt ion beams. Impedance characteristics of these ion diodes deviate strongly from simple space‐charge‐limited flow, particularly in the higher power experiments. An examination of recent data has yielded an empirical voltage‐current relationship with surprising implications, including a ‘‘critical voltage’’ limit.

ISSN:0021-8979    

DOI:10.1063/1.334511

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Theoretical investigation of traveling wave excitation using the property of photon addition has been carried out in a 50‐cm‐long TE N2laser tube with ten separated discharge sections. The laser power outputs under traveling wave excitation have been calculated numerically with varying gas pressures from 30 to 85 Torr and applied voltages from 14 to 21 kV, and compared with those of simultaneous excitation. Theoretical results show that the laser peak power increases with increasing applied voltage, and has a maximum value at gas pressureP&bartil;60 Torr. The laser pulse width is narrowed and the laser power is doubled under the traveling wave excitation, compared with simultaneous excitation. Experimental confirmation also has been conducted. Experimentally observed gas presssure dependence of output power agrees qualitatively well with theoretical results. The maximum discrepancy in the absolute values between theory and experiment is approximately 50%.

ISSN:0021-8979    

DOI:10.1063/1.334458

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The presence of water vapor in the annealing atmosphere during Ti:LiNbO3optical waveguide fabrication prevents Li out‐diffusion, inhibits LiNb3O8growth, and furthermore decomposes this phase if already formed. As a consequence, the TiO2and the mixed oxide (TixNb1−x)O2growth kinetics change. A proton in‐diffusion in LiNbO3with OH−defects and (Li1−yHy)NbO3molecule formation is suggested to explain these effects and to account for the detected increase of absorbance at 3480 cm−1.

ISSN:0021-8979    

DOI:10.1063/1.334459

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The far‐field supermode patterns of a phase‐locked multiple‐stripe quantum‐well heterostructure (QWH) laser diode are described as a function of injection current and emission wavelength, the latter controlled by an external grating. The external‐grating cavity is used to isolate single or multiple supermodes of the multiple‐stripe QWH laser (Pout>170 mW cw, &lgr;∼7400 A˚). The progression of supermode patterns consists of a discrete set of mode configurations for each longitudinal mode of the spectrum. The progression is cyclic with a ∼2.8‐A˚ period which corresponds to the longitudinal mode spacing of the diode. Under high gain conditions, i.e., near the center of the recombination‐radiation spectrum or at higher current levels, continuous tunability is observed with gradual transitions between supermode eigenstates. As the gain is reduced (low current), the number of supermodes observed decreases until only the in‐phase pattern, i.e., each emitter at the same phase, remains above threshold. The far‐field patterns range from a double‐lobe pattern with a 10° peak separation (5 &mgr;m between emitter phase reversals) to a narrow (<2° full angle half power) single‐lobe in‐phase pattern. The experimental data are compared to the results of coupled‐mode analysis.

ISSN:0021-8979    

DOI:10.1063/1.334460

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Short wavelength Alx’Ga1−x’As‐AlxGa1−xAs (x’∼0.85,x∼0.22) quantum‐well heterostructure (QWH) laser diodes (well sizeLz≊400 A˚) that operate continuously (cw) at 300 K are subjected to hydrostatic pressure (≲12 kbar). The emission spectrum and the light intensity versus current (L‐I) curves are monitored to determine the pressure dependence of the direct (&Ggr;) band gap and the threshold current. The band gap exhibits a linear pressure dependence with a noticeable change in slope at ∼4.5 kbar, similar to previously reported results for AlxGa1−xAs‐GaAs QWH diodes. The threshold current increases monotonically with pressure, reflecting the increasing loss of carriers to theXandLbands. The short‐wavelength cw limit of the system, i.e., a gain‐guided laser with a 400‐A˚ AlxGa1−xAs (x∼0.22) quantum well and no separate waveguide region, is determined to be ∼6980 A˚.

ISSN:0021-8979    

DOI:10.1063/1.334461

出版商:AIP    

年代:1985

数据来源: AIP