摘要:

A technique is suggested for creating anisotropic and emissive carrier distributions in semiconductors or other crystals at low temperatures. As an example, application of the technique in the re‐entrant (negative‐mass) regions of heavy holes in germanium and silicon, in conjunction with cyclotron resonance using circularly polarized microwaves, is discussed. These distributions are expected to be short‐lived (of order 0.2 to 5 m&mgr;sec), but more anisotropic than those obtained so far in these regions by applying steady‐state optical excitation alone. The nonequilibrium distributions would be created by excitations (pulsing, for example) with risetime shorter than the carrier‐phonon scattering time. Recently, the increasing purity of materials and speed of electronic instruments have approached the theoretical requirements of this method.

ISSN:0021-8979    

DOI:10.1063/1.1728279

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Principles of a varied group of new semiconducting, piezoresistive stress and strain transducers are outlined. These devices have in common the utilization of the transverse or shear piezoresistive effect. One group of devices consists of gauges in the form of a thin rectangular sheet which is bonded to the test piece, and whose resistance change can be expressed as a simple function of the principal stresses in the gauge. Two special gauges in this group are described. In one, the resistance change is proportional to the sum of the principal biaxial stresses for any orientation of the gauge on the test piece. In the other, the resistance change is proportional only to longitudinal stress components, being independent of transverse stress components. Also described are: a four‐terminal gauge for complete determination of biaxial stresses, full‐bridge gauges made from a single crystal, load cells of low compliance, new torque transducers, and diffusion techniques for making some of the foregoing. The devices are illustrated in terms of germanium and silicon but extension to other semiconductors is straightforward.

ISSN:0021-8979    

DOI:10.1063/1.1728280

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

In semiconductors with extremely low majority carrier densities, the conductivity of the surface space charge region can be very different from the conductivity of the bulk. This paper demonstrates that the conductivity of this surface space charge region can be materially altered by the application of a magnetic field which is perpendicular to the direction of current flow. A tentative prototype model of this effect is presented which not only illustrates the mechanisms of importance, but also is sufficiently accurate to enable one to estimate the order of magnitude of the effect for certain experimental conditions. This model suggests that this effect may find application in magnetoresistance and/or negative resistance devices and might prove useful in the measurement of surface parameters.

ISSN:0021-8979    

DOI:10.1063/1.1728281

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A method is described for preparing large single crystals of cuprous oxide by oxidation of monocrystalline copper. The initial oxidation is performed slowly at low oxygen pressure and temperature, to promote oriented growth of the oxide film. The cuprous oxide crystals obtained from the oxidation process showed subgrain boundaries which were removed by subsequent annealing.

ISSN:0021-8979    

DOI:10.1063/1.1728282

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The electrical conductivity is calculated for some typical seeded gases of magnetohydrodynamic interest. The electron density is obtained using Saha's equation. A method is developed for calculating electron mobility in gas mixtures, taking account of the variation of the scattering cross section with energy. Scattering by ions is also considered. Results are presented for several gases seeded with small amounts of Cs or K in the temperature range from 2000° to 4000°K.

ISSN:0021-8979    

DOI:10.1063/1.1728283

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The activation energy and activation volume for the creep of high‐purity lead were obtained by the method of rapidly varying the temperature and pressure. The activation energy was found to be 1.18±0.03 ev and the activation volume was found to be (24.2±0.6)×10−24cc or 0.80 atomic volume.

ISSN:0021-8979    

DOI:10.1063/1.1728284

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Emission fluctuations in five different types of tungsten‐based barium dispenser cathodes have been measured as functions of both frequency and current density. Two of the cathodes were of theLvariety and the remainder of the ``impregnated'' variety. TheLcathode spectra show that the emission fluctuations are caused by fluctuations in the number of adsorbed atoms on the tungsten emitting surface. The amplitude of the fluctuations is governed by the average surface coverage and theoretical studies indicate that the shape of the spectra is governed by the diffusion processes by which the surface is replenished.The results from the impregnated cathodes indicate that the contribution of the impregnant in the pore ends to the total noise is only significant when the pore ends supply an appreciable fraction of the total emission from the cathode, the majority of the surface, which is barium activated tungsten, behaving as anLcathode surface.

ISSN:0021-8979    

DOI:10.1063/1.1728285

出版商:AIP    

年代:1961

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1728323

出版商:AIP    

年代:1961

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1728325

出版商:AIP    

年代:1961

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1728326

出版商:AIP    

年代:1961

数据来源: AIP