摘要:

In base‐to‐emitter diodes ofp‐n‐pgermanium transistors biased in reverse direction far below breakdown, bistable current fluctuations have been observed. These fluctuations show the typical waveform of a random telegraph signal. Its statistical properties have been analyzed. The mean‐value crossing‐time intervals of current measured by a multichannel pulse‐height analyzer turned out to be independent of reverse voltage but dependent upon temperature. Detailed experimental data are given.

ISSN:0021-8979    

DOI:10.1063/1.1708950

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The electrostatic field in the neighborhood of a slender, axisymmetric conductor is expanded in prolate‐spheroidal harmonics to obtain approximations to the capacitance, the dipole moments induced by both axial and transverse fields, and the induced charge on a grounded boss in a uniform field. The capacitance calculated for a right‐circular cylinder with &dgr;=diameter/length<1 is found to be within 5% of the more accurate results calculated by Smythe. The corresponding comparisons for the dipole moments and the induced charge on a cylindrical boss are less impressive for non‐small &dgr; but suggest the general utility of the slender‐body approximation for &dgr; of the order of 10−1or less.

ISSN:0021-8979    

DOI:10.1063/1.1708951

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The thin gold films are evaporated in an ultrahigh vacuum system onto clean and air‐contaminated rocksalt crystals at liquid‐nitrogen temperature. The structure and orientation of the deposits are investigated with an electron microscope. The changes in film topology during the warmup to room temperature, caused by surface diffusion, can effectively be prevented by covering the films with a carbon layer immediately after their deposition at 80°K. Comparison of stripped carbon‐covered films with those examined by transmission through thinned‐down areas of the rocksalt shows that the stripping causes only minor changes in film topology. Changes in structure and orientation of the gold films with varying substrate temperature are investigated over a wide range of temperature. The results are discussed with respect to the work in the epitaxial temperature region.

ISSN:0021-8979    

DOI:10.1063/1.1708952

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The macroscopic strength of an oriented medium is investigated under the assumption that processes of breaking and reforming of microscopic components in the medium may occur. The differential equation governing the time‐dependent variation of the number of load‐carrying components is considered. Emphasis is placed on the study of the effect of the reformation processes on the stress‐time‐to‐fracture behavior. It is suggested that under small loads these processes may be responsible for the frequently observed phenomena of the deviation from linearity of the strength and logarithm of time‐to‐fracture relationship. An attempt is also made to compare theoretical results with some reported experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1708955

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The carrier removal produced in 10‐ and 100‐&OHgr;·cm, vacuum‐floating‐zone,n‐type silicon by neutrons from a bare235U reactor was measured and compared with that produced by 14‐MeV neutron irradiation of the same samples. Carrier removal rates were obtained from conductivity measurements at 283°K following irradiations at 300°K. The measured 14 MeV‐to‐reactor‐neutron‐damage ratio is 2.8±0.5 for the 10‐&OHgr;·cm silicon, and 2.9±0.6 for the 100‐&OHgr;·cm silicon. Very similar isochronal annealing was observed between 300 and 500°K following 14‐MeV and reactor‐neutron irradiation. This suggests that 14‐MeV and reactor‐neutron irradiation produce the same kinds of defects inn‐type silicon. Total scattering cross‐section data for silicon, information on nonisotropic scattering, and the Lindhard model for silicon recoil energy loss to ionization were used to calculate the average energy per cm spent in silicon displacement collisions per incident neutron between 0.2 and 14 MeV. There is general agreement between the calculated energy spent in silicon displacements as a function of neutron energy and the energy dependence of the reported monoenergetic neutron irradiation‐produced carrier removal rates inn‐type silicon. Dividing the predicted energy spent in collisions per neutron‐cm by the carrier removal rate gives an average of 0.85 keV with a standard deviation of 0.38 keV per carrier removed for previously reported monoenergetic neutron irradiations. Using the carrier removal rates measured at 283°K for the 10‐&OHgr;·cmn‐type silicon of this investigation, the average energy spent in collisions per carrier removed is 1.25±0.15 keV for the reactor neutron irradiation and 0.94±0.08 keV for the 14‐MeV neutron irradiation.

ISSN:0021-8979    

DOI:10.1063/1.1708956

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Plasma energy density, conductivity, and temperature were measured at various pressures ranging from 3 to 120 kbar. The experimental work was conducted in two parts; plasmas with pressures to 15 kbar were formed by capacitor discharges in water, and plasmas with higher pressures were formed by detonating 10 g of PETN in the water adjacent to the electrical discharge path. At 9.4 kbar and 35 000°K, the energy density was 15 J/mm3. An equation of state based upon the Debye shielding theory, without accounting for the distortion of electron quantum states, predicts an energy density of only 3.3 J/mm3. An approximate calculation is presented which accounts for these distortions, and furnishes an estimate of particle densities from measured energy densities. A peak energy density of 75 J/mm3was obtained at 117 kbar and 1029atoms/m3. At 10 kbar and 35 000°K, the conductivity was 3×105(&OHgr; m)−1and increased with pressure. At 110 kbar and 10 000°K, the conductivity was 2.5×105(&OHgr; m)−1and also was an increasing function of pressure.

ISSN:0021-8979    

DOI:10.1063/1.1708957

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A critical evaluation is made of the procedure and the important parameters involved in estimating the stacking‐fault energy &Ggr; from x‐ray diffraction measurements of deformed materials. The published data for the Ag‐In and the Cu‐Zn system are carefully analyzed and compared with results obtained by transmission electron microscopy. For deformed filings, the dislocation density, and hence the mean square strain ⟨&egr;2⟩hkl, vary with composition, as does the stacking‐fault probability &agr;. Since &Ggr;∝&agr;−1⟨&egr;2⟩hkl, the value for the proportionality constant must be known to obtain &Ggr;. This requires a knowledge of the dislocation configuration, principally in terms of barriers and pile‐ups of extended dislocations. Within the limits of uncertainty of this information, an assessment of the proportionality constant can be made so that reasonably good consistency with transmission electron microscopy results is obtained. In this way, estimates (good to ±25%, probably) of &Ggr;=18 erg/cm2for pure silver and &Ggr;=65−74 erg/cm2for pure copper could be calculated.

ISSN:0021-8979    

DOI:10.1063/1.1708958

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The compressibility of 30% Ni‐70% Fe (wt %) in the fcc phase is investigated from atmospheric pressure to 40 kbar with shock‐wave loading techniques. The experiments are accomplished utilizing projectile impact techniques with stress profile measurements by the quartz gauge. A sharp change in compressibility indicates a second‐order ferromagnetic Curie point transition at a stress of 25 kbar and a volume of 0.9807V0. The coefficient of Curie temperature change with pressure is found to be −5.8±0.3°C kbar−1. The agreement of this value with previous magnetic measurements, along with the anomalously large compressibility below the transition and the large decrease in compressibility at an elevated temperature, clearly indicates that this transition is a ferromagnetic to paramagnetic transition. Values for the change of thermal expansion and specific heat at the transition are computed from the Ehrenfest relations. These values are consistent with the magnetic character of the transition and give a complete description of the thermodynamic properties of the transition. To provide more compressibility data on various types of ferromagnetic materials, a few additional measurements are reported for Invar and 30% Ni‐70% Fe in the bcc phase.

ISSN:0021-8979    

DOI:10.1063/1.1708959

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The aluminumKand ironLemission bands and the aluminumK&agr;3andK&agr;4satellite lines from a series of aluminum‐iron binary alloys have been studied using 6‐kV electron excitation and a flat crystal x‐ray vacuum spectrometer equipped with a flow proportional counter. It is found that the AlKband energy position and the AlK&agr;4/K&agr;3intensity ratio are both linearly dependent on alloy composition. As the aluminum concentration is lowered, the AlKband intensity maximum shifts to lowery energy and the band becomes more symmetrical in shape. In general, these results are very similar to those obtained previously from the aluminum‐nickel system. The FeLIIIband undergoes very little change in shape but shifts to higher energy as the aluminum‐to‐iron ratio is increased. The spectral changes are interpreted as indicating that the predominately metallic bond in the pure metals acquires a certain amount of covalent‐like character in the alloys with the aluminum atoms behaving as electron donors.

ISSN:0021-8979    

DOI:10.1063/1.1708960

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A general formulation for the study of electrostatic oscillations and streaming instabilities in bounded and unbounded Vlasov plasmas with transverse density gradients in a strong axial magnetic field is presented. It is found that the behavior of the plasma depends on a parameter which is a function of geometry, scale of inhomogeneity, and wavelength. Using this formulation, several experimentally realistic configurations have been studied. Two results obtained are of special interest. They are (1) for waves with the same wavelength, a density inhomogeneity and/or boundary increase Landau damping. (2) Under appropriate conditions, depending on the geometry and the degree of inhomogeneity, it is not possible to excite the two‐stream instability for any drift velocity. Previous theories of uniform plasmas appear as special cases in this general treatment.

ISSN:0021-8979    

DOI:10.1063/1.1708961

出版商:AIP    

年代:1967

数据来源: AIP