摘要:

We have studied the effects of a constant external electrostatic field on the photoemissive characteristics of thin films of iron. The thin films were obtained by thermal evaporation and condensation on a silica substrate. Thickness was between 0.5 and 110 nm. The direction of the field is perpendicular to the surface of the film; its intensity varies by a few V m−1at 510 000 V m−1. With all the films, the greater the field is, the lower the work function is. The value of this lowering depends on the thickness and structure of the film. It is maximum in absolute value and equal to about 0.07 eV for a thickness of about 2 nm. When the field varies, the photoionization coefficient remains constant within measurement precision for the same film. A possible interpretation, based on the variations of the electrostatic double layer on the surface, is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1663478

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A gas bubble chamber was used to study the prebreakdown mechanism in diethyl ether. The liquid was saturated with CO2gas at a pressure of 9–13 kg/cm2and then further compressed to a pressure of 40–45 kg/cm2. The liquid was then rapidly expanded 4–6% in volume, causing it to become temporarily supersaturated. At that time an impulse voltage of about 33 kV/was applied between two needle electrodes (gap length 3.2 mm) in the liquid. The resultant bubble figures, which represent electron emission from the cathode, were recorded photographically. The time lag from the application of the impulse voltage to the growth of bubbles of observable size was about 0.8–1.0 msec. This value agrees with the results obtained by using an ordinary bubble chamber.

ISSN:0021-8979    

DOI:10.1063/1.1663479

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Time‐of‐flight measurements have been made for hydrogen, nitrogen, and metastable helium, argon, and nitrogen beams emerging from a cooled discharge source, in order to determine the velocity distributions in these beams. We observe typically 85% H and 15% H2relative beam number densities from a hydrogen discharge, and 10% N and 90% N2relative beam number densities from a nitrogen discharge. The results show the effects of variation of the source gas pressure, microwave power, cooling rate, and in the case of a hydrogen discharge, the effect of adding water vapor to enhance dissociation. Argon seeding of the hydrogen discharge has been investigated as a means of determining the beam temperature without resorting to direct velocity or time‐of‐flight measurements. Some results are also given for room‐temperature and low‐temperature beams, obtained without a discharge.

ISSN:0021-8979    

DOI:10.1063/1.1663480

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The adiabatic elastic constants were determined for niobium and for its alloys containing 1.4, 3.6, and 6.0 at.% zirconium. Thec11,c12, andc44constants as well as the shear constantC′= (1/2)(c11−c12) and the bulk modulus were tabulated between 4.2 and 290 K. The unusual temperature dependence of the shear constantc44found in niobium was also observed in the alloys. The Debye temperatures were computed from the constants at 4.2 K.

ISSN:0021-8979    

DOI:10.1063/1.1663481

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A plasma created by exploding a thin lithium wire in a vacuum is analyzed using a magnetohydrodynamic (MHD) model. The two‐temperature MHD equations including finite thermal conductivity and electrical resistivity are derived in one‐dimensional cylindrical geometry. The resulting system of six coupled nonlinear partial differential equations in six unknowns is then solved numerically. Results of the calculation including spatial dependence of density, temperature, and magnetic field and time dependence of the radial profile and average temperature are given. These calculated properties are compared to available experimental results, giving favorable agreement.

ISSN:0021-8979    

DOI:10.1063/1.1663482

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The behavior of amorphous Si in contact with Ag films and Ge in contact with Al films has been studied at temperatures well below those at which any liquid phase is present. MeV4He+ion backscattering techniques, transmission electron diffraction, scanning electron microscopy, and electron microprobe analysis have been used. We find that of the many possible reactions which carry the amorphous Si or Ge into their crystalline forms the reaction predominating under our experimental conditions consists of dissolution, diffusion, and crystal growth. During isothermal heat treatment, the semiconductor film is dissolved into the metal film where it diffuses and precipitates as crystalline Si or Ge. These processes are solid‐solid reactions, since this behavior is observed over temperatures of 300°C to as low as 100°C for Ge/Al, compared to the 424°C eutectic in this system. In Si/Ag, this behavior was observed from 700 to 400°C, compared with the 840°C eutectic.

ISSN:0021-8979    

DOI:10.1063/1.1663483

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Heat treatment of evaporated Si in contact with Ag films and Ge in contact with Al films results in the formation of precipitates of the semiconductor in a metal matrix. The structure of these precipitates was studied by transmission electron microscopy and diffraction (TEMD) and MeV4He ion channeling techniques. TEMD studies showed that the semiconductor precipitates were crystalline in nature. Channeling techniques showed that the crystallites did not have a simple orientation relationship with the underlying single‐crystal substrate.

ISSN:0021-8979    

DOI:10.1063/1.1663484

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Wires made of materials having high boiling points were exploded in an evacuated vessel of coaxial design. It was found that the influence of the radial electric field on the x‐ray emission as well as on the initiation of the shunting discharge was small. In addition, the shunting discharge and the vaporization of the wires were studied by a Kerr‐cell camera. Tungsten and molybdenum wires were found to vaporize in a nonuniform way. A model to explain this behavior is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1663485

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

ZnTe&sngbnd;CdS heterojunction LED, which was prepared on the ZnTe substrate by CdS vapor growth, showed the red light emission at 300°K. The EL spectra had a peak at 1.78–1.80 eV at 300°K, and two peaks at about 2.10 and 1.55 eV at 77°K. The existence of the ZnxCd1−xTe mixed crystal with a graded band structure at the heterojunction interface was shown from the results of the photovoltage spectra and transmittance analysis of the heterojunction. The formation of the mixed crystal was found to be due to Cd diffusion into the ZnTe substrate during the epitaxial growth. From photoluminescence measurements, it is concluded that the red emission of ZnTe&sngbnd;CdS LED may originate from the ZnxCd1−xTe mixed crystal layer. Thus, efficient red emission could be obtained in our ZnTe&sngbnd;CdS heterojunctions on account of the mixed crystal layer, which reduced high‐energy barriers for electrons and holes.

ISSN:0021-8979    

DOI:10.1063/1.1663486

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Simultaneous measurements of electrical conductivity and flow stress have been made onp‐ andn‐type CdTe single crystals deformed in compression at room temperature. Observed changes in conductivity always correspond to a shift of the Fermi energy towards the conduction band and are consistent with the creation of an excess of dislocation donors. An energy‐band diagram for the native point‐defect states and dislocation states in CdTe is formulated based upon observed electrical, optical, and mechanical behavior.

ISSN:0021-8979    

DOI:10.1063/1.1663487

出版商:AIP    

年代:1974

数据来源: AIP