摘要:

Surface‐wave acoustoelectric domains were excited in a photoconductive CdS crystal. It was verified experimentally that the generation of these domains was triggered by an external signal. An adhesive tape stuck on the propagation plane prevented the excitation of the domains.

ISSN:0003-6951    

DOI:10.1063/1.1655427

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Based on the theory of surfons, we present a formalism to calculate the attenuation rate of elastic surface waves at low temperatures in the high‐frequency region. A general formula for the attenuation rate due to the cubic anharmonic terms in the elastic energy of an isotropic elastic continuum is given by means of a temperature‐dependent Green's function. In a frequency region between 20 and 40 GHz atT=1°K, our result shows quite different frequency and temperature dependence&ohgr;1+n T4−n (1.9 ≲ n ≲ 2.2)from that obtained in the low‐frequency region.

ISSN:0003-6951    

DOI:10.1063/1.1655428

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An acoustic wave storage device capable of storing an acoustic surface wave signal for times of up to several milliseconds is described. The principle of the device is based on that of the acoustic surface wave convolver, with the information stored in surface states in silicon. It is expected that the storage time will ultimately be as much as 10–30 msec for signals with modulation frequencies of tens of megahertz. At the present time, we have seen storage of pulses approximately 0.4 &mgr;sec long for times of approximately 2 msec, but some of these early devices seem to be capable of yielding storage times as long as 7 msec.

ISSN:0003-6951    

DOI:10.1063/1.1655429

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Convolution of two signals has been obtained in real time using the efficient diffraction of laser light from acoustic surface waves. Two pulse‐modulated 45‐MHz surface waves are launched from the two ends of a surface wave delay line. Laser light enters the delay line from one side, interacts with two oppositely directed parallel acoustic beams along their widths, and exits from the other side. The diffracted light, after an optical Fourier transformation, is incident on a photodiode which produces an electrical output containing the desired convolution signal. With the present 5‐&mgr;sec interaction length and 9‐MHz transducer bandwidth, the time‐bandwidth product is 45.

ISSN:0003-6951    

DOI:10.1063/1.1655430

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Low‐energy (≃ 10 eV) electron bombardment on an SiO2layer gives rise to strong trapping at the surface and to a positive space‐charge build‐up near the Si&sngbnd;SiO2interface. The density, the capture cross section, and the energy level of the traps have been evaluated using, respectively, the constant current charging process and the quantum yield of vacuum photoemission versus wavelength.

ISSN:0003-6951    

DOI:10.1063/1.1655431

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new nematic material in which &egr;∥exhibits a dielectric loss in the audio‐frequency range is reported. At 25 °C&Dgr; &egr;=(&egr;∥−&egr;⊥)reverses sign at 2.5 kHz and can be as positive as 6.2 at low frequencies and as negative as −2.2 at high frequencies; the activation energy for the loss is 0.91 eV. The availability of a dielectric anisotropy of either sign depending on the frequency of the applied field allows the electrical orientation of the material with its optic axis either parallel or perpendicular to the electrodes. The possibilities for improving the voltage threshold and dynamic response of electro‐optical effects by means of a two‐frequency addressing scheme are demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.1655432

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A monolithic convolver using rf‐sputtered zinc oxide deposited on silicon was constructed and operated at a center frequency of 120 MHz. The electronic efficiency obtained with this deviceF = Pout/Pin1Pin2, using 100‐&OHgr; cm silicon, was −70 dB m. This corresponds to an input‐output efficiency of approximately −50 dB with a 20‐dB m reference signal. These results agreed well with our theoretical expectations for the device. The theory predicts that with a properly optimized device, the electronic efficiencyFcan be of the order of −50 dB m.

ISSN:0003-6951    

DOI:10.1063/1.1655433

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The radial proton emission from a 5‐MV 50‐kA electron‐beam diode with polyethylene anode has been spatially and spectrally measured with pinhole cameras and ion‐sensitive vacuum diode detectors. The spatial measurements indicate that the protons originate from electron‐beam pinches less than 200 &mgr;m in diameter. The proton spectrum measured between 80 keV and 3 MeV is in qualitative agreement with published data for a computer simulation of proton acceleration via the relativistic electron‐ion two‐stream instability in a tightly pinched electron beam.

ISSN:0003-6951    

DOI:10.1063/1.1655434

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Expansion due to illumination (photoexpansion) and contraction due to heat treatment (``thermal contraction'') of As&sngbnd;Se&sngbnd;(S)&sngbnd;Ge glass films have been observed utilizing the bimetal structures. This property is related to the reversible photodarkening effect of these chalcogenide glass films.

ISSN:0003-6951    

DOI:10.1063/1.1655435

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Short‐circuit capacitance data, for solar cells with base resistivities in the range 0.5–90 &OHgr; cm, indicate a junction capacitance injected carrier concentration of the order 1014cm−3at photovoltaic current densities of 25 mA/cm2. This short‐circuit injected carrier concentration, which is usually assumed to be zero, is nine orders of magnitude greater than the equilibrium concentration. This condition is explained in terms of an expanded interpretation of the Shockley injection relation where the chemical potentialKof the electrochemical potential, &mgr; =K−eV, dominates injection rather than the electrostatic potentialV.

ISSN:0003-6951    

DOI:10.1063/1.1655436

出版商:AIP    

年代:1974

数据来源: AIP