摘要:

We describe a low‐threshold, low‐internal‐loss, multiple‐quantum‐well ridge waveguide laser operating at 1.55‐&mgr;m wavelength and grown by chemical‐beam epitaxy. With a high‐reflection coating applied to one facet, it can operate CW to 100 °C. The laser exhibits single transverse‐mode output and 6‐GHz bandwidth. Processing utilizes a combination of self‐aligned reactive‐ion etching and wet chemical etching. Nearly 100% threshold and quantum efficiency yield of devices in bar form was obtained as a result of the excellent material uniformity, precision process control, and process uniformity over the wafer. This suggests that the present laser may be a potential candidate for low‐cost light source applications.

ISSN:0003-6951    

DOI:10.1063/1.105681

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report detailed two‐dimensionalinsitumeasurements of electron density inside an injected‐beam crossed‐field amplifier operating at 150 MHz. It is demonstrated that during amplification there is a spatial redistribution of the cycloidal electron beam as electrons are drawn to the anode. These measurements have been compared with a numerical simulation [G. E. Dombrowski, IEEE Trans. Electron. Devices35, 2060 (1988)] which predicts a change in electron trajectories but gives a larger electron loss than was measured.

ISSN:0003-6951    

DOI:10.1063/1.105682

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The electron energy and density in a diamond microwave plasma‐assisted chemical vapor deposition reactor are determined using a double‐electrostatic‐probe technique. For a reactor feed gas composition of 2% CH4, 1% O2in H2, electron temperatures of 6 eV and electron densities of ∼1.0×1011cm−3were measured. These values are consistent with optical emission spectroscopic results. The electron temperature is not strongly dependent on the amount of O2added to the reactor feed mixture, indicating that the plasma essentially retains the energetic parameters of a hydrogen plasma.

ISSN:0003-6951    

DOI:10.1063/1.105683

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report measurements of the plastic relaxation of InGaAs layers grown above critical thickness on GaAs substrates. The relaxation is accurately hyperbolic, proportional to the reciprocal of the layer thickness, in agreement with a recent geometrical theory of critical thickness [D. J. Dunstan, S. Young, and R. H. Dixon, J. Appl. Phys.70, 3038 (1991)]. At large thicknesses, work hardening is observed which leads to a residual strain dependent on the original misfit.

ISSN:0003-6951    

DOI:10.1063/1.105684

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on free‐standing ultrafine fibers formed using the gas‐evaporation method in the presence of electric fields. Materials up to 10 cm in length have been prepared in this way. Electrical measurements on Pd fibers 3 mm in length and about 200–300 A˚ in diameter are given.

ISSN:0003-6951    

DOI:10.1063/1.105685

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Glass bars and plates were subjected to impact loading. Failure waves were observed to propagate behind the compression waves. Material traversed by the failure wave suffers total loss of tensile strength and substantial drop in shear strength. Failure wave propagation velocities exceed the maximum crack propagation speed, but are not constant. In bars, failure wave speed range from 2.3 to 5.2 mm/&mgr;s, increasing with increasing impact velocity; in plates, the wave speed is about 2 mm/&mgr;s. The failure is ‘‘explosive’’ in nature, leading to radial expansion in bars and an increase in mean stress in plates.

ISSN:0003-6951    

DOI:10.1063/1.105686

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The successful growth of ultrathin CoGa on GaAs by MBE is demonstrated. The crystalline quality of the films is verified byinsituRHEED, RBS, and x‐ray rocking curve. Transport studies are performed in the temperature range of 4 to 300 K for layer thickness from 10 to 730 A˚, and all the films are found to be electrically continuous. The Markowitz’s model [Phys. Rev. B15, 3617 (1977)] of the electrical resistivity is applied to analyze the measured data. Finally, the specularly scattering probability of these thin films is studied using Fuchs’ theory [Proc. Cambridge Philos. Soc.34, 100 (1938)].

ISSN:0003-6951    

DOI:10.1063/1.105687

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Millimeter‐sized single crystals of C60were grown by sublimation of C60powder in a vacuum for 6–24 h. The crystals had excellent facets, were free of C70or solvent, and showed face‐centered cubic symmetry with a very small mosaic spread down to 0.01°.

ISSN:0003-6951    

DOI:10.1063/1.105688

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Atomic force microscopy has been used to characterize wear and oxidation of transition metal dichalcogenide surfaces. Sequential images recorded on molybdenum disulfide (MoS2) and niobium diselenide (NbSe2) surfaces show that wear proceeds at defects, and that MoS2wears at least five times more slowly than NbSe2. Images of thermally treated MoS2and NbSe2further demonstrate that oxidation creates surface defects on both materials. However, for similar oxidation conditions, NbSe2surfaces show extensive degradation, while MoS2surfaces only exhibit isolated defects. The implications of these results to understanding the tribological properties of the transition metal dichalcogenides are discussed.

ISSN:0003-6951    

DOI:10.1063/1.105689

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

There are good indications that the deep level around 0.45 eV induced by oxygen acts as an effective electrical recombination center in heterojunction bipolar transistors with a graded band‐gap AlGaAs emitter‐base junction. The transistor, with a concentration of the 0.45 eV level on the order of about 5×1015cm−3in the junction region, shows a very small current gain of 3–4, down from more than 30 at a collector current density of 1×103A/cm3. This reduction is greater than the previously reported one by the level approximately 0.6 eV in heterojunction bipolar transistors. The level about 0.45 eV is detected from the junction region that has an oxygen atom concentration of more than 1018cm−3. This level may also act as an optically nonradiative recombination center.

ISSN:0003-6951    

DOI:10.1063/1.105690

出版商:AIP    

年代:1991

数据来源: AIP