摘要:

A new technique using radioactive31Si (half‐life =2.62 h), formed in a nuclear reactor, as a marker for studying silicide formation is described. A few hundred angstroms of radioactive silicon is first deposited onto the silicon substrate, followed immediately by the deposition of a few thousand angstroms of the metal. When the sample is heated, a silicide is first formed with the radioactive silicon. Upon further silicide formation, this band of radioactive silicide can move to the surface of the sample if silicide formation takes place by diffusion of the metal or by silicon substitutional and/or vacancy diffusion. However, if the band of radioactive silicide stays at the silicon substrate interface it can be concluded that silicon diffuses by interstitial and/or grain‐boundary diffusion. This technique was tested by studying the formation of Ni2Si on ⟨100⟩ silicon at 330 °C. From a combination of ion‐beam sputtering, radioactivity measurement, and Rutherford backscattering it is found that the band of radioactive silicide moves to the surface of the sample during silicide formation. From these results, implanted noble‐gas marker studies and the rate dependence of Ni2Si growth on grain size, it is concluded that nickel is the dominant diffusing species during Ni2Si formation, and that it moves by grain‐boundary diffusion.

ISSN:0003-6951    

DOI:10.1063/1.89230

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Local thicknesses of a GaAs epitaxial layer grown on a mesa stripe by semiparallel Ga and As4molecular beams have been found to be proportional to cos&fgr;Ga, where &fgr;Gais a local incident angle of the Ga beam to a local crystal growing surface. Submicron‐thick three‐dimensional GaAs‐Ga1−xAlxAs multilayers have been grown self‐aligningly on corrugated structures with a 8‐&mgr;m period. The layer thicknesses and AlAs compositions (x) are also interpreted by the local incident angles of Ga and Al beams, while evidence of atom diffusion is revealed.

ISSN:0003-6951    

DOI:10.1063/1.89231

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Coupled ferroelastic‐ferroelectric domains in the rare‐earth molybdates can be used to provide electronically variable analog delay in simple acoustic delay line structures. Delay variations of ∼3% for surface acoustic waves and 12% for bulk longitudinal waves are demonstrated with gadolinium molybdate [Gd2(MoO4)3] crystals. Estimates of a number of parameters useful in evaluating device performance are made from experimental measurements.

ISSN:0003-6951    

DOI:10.1063/1.89232

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Electrical resistivity measurements have been used to observe damage production rates for Cu, Nb, and Pt irradiated with high‐energy d‐Be neutrons at 4.2 °K. The neutrons were generated at the Oak Ridge Isochronous Cyclotron by the reaction of 40‐MeV deuterons incident on a thick Be target. The resulting neutron energy spectrum was broadly peaked near 15 MeV. Damage production was proportional to fluence up to 4×1015n/cm2, and was approximately three times greater than for the same fluence of fission neutrons in these materials. This result is in good agreement with predictions based on damage energy calculations.

ISSN:0003-6951    

DOI:10.1063/1.89233

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Excellent selective black absorbers for solar radiation, with solar absorptivity of over 0.9 and infrared emissivity of less than 0.1, have been obtained by using rf sputtering to coat metal substrates with a Cr2O3/Cr cermet film, then with a Cr2O3antireflection coating. By determining the optical constants of Cr2O3/Cr films over the composition range up to 35 vol% Cr, it was found that films containing 29 vol% Cr are nearly optimum for this application. The optical and chemical properties of absorbers made with such films are quite similar to those obtained with electroplated Cr‐black coatings. This similarity suggests that the electroplated coatings are actually Cr2O3/Cr cermets comparable in composition and microstructure to the sputtered films.

ISSN:0003-6951    

DOI:10.1063/1.89234

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The threshold for collisionless dissociation of SF6, SiF4, and CF2Cl2by focused CO2laser radiation has been measured. This threshold is a laser pulse energy effect and, within experimental error, is found to be the same for all three gases. Provided collisions cannot occur during the laser pulse, the degree of dissociation produced depends only on the energy in the pulse, which is consistent with simple adiabatic vibrational heating of the molecules by the laser.

ISSN:0003-6951    

DOI:10.1063/1.89237

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Laser excitation of metal vapors and gases in four types of hollow cathodes employing transverse electrical discharges is discussed. A water‐cooled slot cathode is demonstrated to provide two distinct laser excitation modes. cw laser action at 7471, 7042, and 6920 A˚ from Al II, which is cathodically sputtered by Ne/H2mixtures and excited in charge‐transfer collisions, is reported. Pulsed laser action at 7065.21 and 7065.17 A˚ from He I, which is excited in direct electron impact collisions in the presence of H2is reported. Laser performance data relating to gas pressures, currents, pulse widths, and gains are presented. The importance of H2admixtures to the laser species is discussed.

ISSN:0003-6951    

DOI:10.1063/1.89238

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

A wavelength‐selective beamsplitter has been realized by fabricating chirped (variable period) grating in an optical waveguide. This beamsplitter can demultiplex a signal traveling in a fiber and send each frequency component to a different fiber.

ISSN:0003-6951    

DOI:10.1063/1.89218

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

We propose a new integrated interferometric reflector (IIR) with electrical control. The IIR is suitable for incorporation in integrated optical devices as a laser reflector.

ISSN:0003-6951    

DOI:10.1063/1.89219

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Distributed feedback Pb1−xSnxTe double‐heterostructure lasers grown by molecular‐beam epitaxy with cw operation up to 50 K are reported. The grating of 1.1‐&mgr;m periodicity operates in the first Bragg order near 800 cm−1(12.5 &mgr;m). Single‐mode operation is obtained over a wide range of diode current and heat‐sink temperature. Continuous current tuning of mode frequency up to 7 cm−1is obtained, and by varying both diode current and heat‐sink temperature complete coverage of the range 795–806.5 cm−1is demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.89220

出版商:AIP    

年代:1977

数据来源: AIP