摘要:

Experimental results on a unique multichannel slab‐type CO2discharge system are presented. The interdigital discharge geometry incorporates both large‐area and multibeam laser array concepts into a single, compact package. Small signal gain and saturation intensity values indicate that this structure is well suited for use in a CO2laser.

ISSN:0003-6951    

DOI:10.1063/1.105220

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We present two‐dimensional electromagnetic computer simulation results performed in order to investigate the focusing properties of self‐magnetically insulated ion diodes. A particle‐in‐cell code self‐consistently computes the electromagnetic fields inside the anode‐cathode gap and an optimization code changes the shape of the anode in order to improve the focusing behavior. It has been shown computationally that in the case of the self‐magneticallyB&thgr;‐insulated diode the power density can be improved by a factor of 7 by changing the anode surface.

ISSN:0003-6951    

DOI:10.1063/1.104546

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In solenoidal beam transport systems, motions in thexandydirections are coupled by thev×Bforce. A two‐dimensional coupled mode description of the beam breakup (BBU) instability is presented; its dispersion relation is derived and compared with the one‐dimensional BBU dispersion relation. In the two‐dimensional description, instability growth is doubled and two additional wave modes are found in the regime of strong focusing. In the weak focusing regime, the two‐dimensional description gives the same dispersion relation as the one‐dimensional model.

ISSN:0003-6951    

DOI:10.1063/1.105219

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Epitaxial Ag(111) films have been grown on mica. They exhibit flat terraces of a few 100 nm diameter, suitable for nanoscale modification with the scanning tunneling microscope (STM). Under ambient conditions, surface modifications of a few nanometers diameter were produced by raising the bias from below 1 V to a bias between 3 and 7 V for less than 50 ns. The steady‐state current could be limited to 2 pA. This means that the modification is initiated while only a few electrons pass the tunneling junction, indicating that it is not a current effect. At positive sample bias, usually holes are formed, while at negative bias hillocks occur. In the case of hole formation, the current does not change significantly on a time scale of 10 &mgr;s. When hillocks are formed, the current may rise after the application of the voltage pulse. It was limited to 4 nA by the external circuitry and remains saturated until the tip is withdrawn on a time scale of milliseconds, i.e., the characteristic for the feedback loop control. Also in this case the modification is not caused by a current effect, since the limiting current would still allow nondestructive STM imaging. It is concluded that the modifications are caused by field evaporation of sample and tip material, respectively.

ISSN:0003-6951    

DOI:10.1063/1.104520

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

CuAu‐I type ordered structures in InGaAs grown on (110)InP substrates by molecular beam epitaxy, have been studied by transmission electron microscopy. In the electron diffraction pattern from the InGaAs, superstructure spots associated with CuAu‐I type ordered structure are found. The intensity of the superstructure spots becomes stronger as the tilting angle of the substrate increases up to 5°. In high‐resolution images of the crystal, doubling in periodicity of 220 and 200 lattice fringes is found, which is associated with CuAu‐I type ordered structure. Moreover, anti‐phase boundaries are very often observed in the ordered regions, which has been suggested by Kuanetal. [Appl. Phys. Lett.51, 51 (1987)]. It is also found that ordering is not perfect, and that ordered regions are plate‐like microdomains lying on planes slightly tilted from the (110) plane. From these results, it is suggested that atomic steps on the growth surface play an important role in the generation of ordered structures.

ISSN:0003-6951    

DOI:10.1063/1.104521

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the first observation of resonant tunneling in the InSb/AlxIn1−xSb material system. Five samples with InSb quantum well thicknesses ranging from 70 to 110 A˚ and Al0.5In0.5Sb barrier thicknesses ranging from 22 to 36 A˚ were grown by molecular beam epitaxy on GaAs(100) substrates at a temperature of 420 °C. The best sample, which had 22‐A˚‐thick barriers and a 110‐A˚‐thick quantum well, displayed a peak‐to‐valley current ratio of 1.4(3.9) at room temperature (77 K) with a corresponding peak current density of 3.6×104A/cm2. Transmission electron microscopy revealed threading dislocations, misfit dislocations, and microtwins in the barrier region.

ISSN:0003-6951    

DOI:10.1063/1.104522

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Boron‐doping spikes in Si have been grown by fast gas switching chemical vapor deposition at 800 or 850 °C using Si2H6in 0.03 or 0.1 atm H2, respectively. The B2H6doping gas was added for 2 s in two ways, viz. during growth, or as a flush while the Si2H6was interrupted. High‐resolution secondary‐ion mass spectrometry (HR‐SIMS) analysis has revealed the sharpest as‐measured SIMS dopant profiles reported for Si grown by deposition from the gas phase. Electrical measurements show the sheet resistivity of the B spikes to be as low as 580 &OHgr;/&laplac;.

ISSN:0003-6951    

DOI:10.1063/1.104523

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In a previous paper it was reported that GaAs, after rapid thermal annealing, exhibited bright regions adjacent to the sample surfaces in the cross‐section cathodoluminescence image. In this report it is shown that these bright bands are associated with the presence of Cu, as indicated by photoluminescence measurements. It is proposed that the Cu diffuses into GaAs during annealing, from residual Cu on the sample surface. To test this hypothesis, samples were treated to alter the residual Cu prior to annealing. Removing the Cu markedly reduced the depth of the bright bands; adding Cu markedly increased the depth, in agreement with the proposed mechanism.

ISSN:0003-6951    

DOI:10.1063/1.104524

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Pseudomorphic In0.18Ga0.82As single quantum wells (QWs) have been grown by metalorganic chemical vapor deposition (MOCVD) on patterned substrates with mesa sizes of 3.5 &mgr;m oriented along [110] and [11¯0] directions. Using a post‐growth masking technique, photoluminescence (PL) has been used to characterize the optical properties of the as‐grown QWs. Our results show the increase of the critical thickness by about 50% for growth on [110] undercut mesa as compared with that on the planar substrate due to the discontinuous growth behavior and no increase of critical thickness of [11¯0] oriented mesas due to the continuous growth behavior and outdiffusion of In from the facet wall of the groove to the mesa top.

ISSN:0003-6951    

DOI:10.1063/1.104525

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have fabricated ultranarrow InGaAs/InP buried quantum well wires by means of electron beam lithography and reverse mesa wet etching. Owing to the reverse mesa etching profile, the lateral dimension of the wires has been reduced to 10 nm. Furthermore, we investigated the optical characteristics of these wires by photoluminescence and observed, for the first time, clear dependence of luminescence wavelength upon the wire width even for wires down to 10 nm, which is well explained by the theoretical calculation. The blue‐shifted shoulder structures were also observed and they were assigned theoretically to be the second quantized level.

ISSN:0003-6951    

DOI:10.1063/1.104526

出版商:AIP    

年代:1991

数据来源: AIP