摘要:

The stability of neutron bombardment damage in Sb‐doped Ge has been investigated by making continuous measurements of the electrical conductivity and Hall mobility following a neutron pulse. Measurements were made in the temperature range from 77° to 308°K with a time resolution of 1 sec. At temperatures near 195°K an initial decrease in conductivity and mobility was followed by an additional decrease which exhibited nearly second‐order kinetics. At 273°K and above, an initial decrease in conductivity and mobility was observed, but was followed by a recovery consistent with an activation energy of 0.68 ev. The void region model of Gossick and Crawford has been employed to explain the initial decrease in mobility and a major portion of the initial decrease in conductivity. The transitory changes in mobility and conductivity after the neutron pulse are considered as changes in the void volumes.

ISSN:0021-8979    

DOI:10.1063/1.1735834

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The performance characteristics of a conventional thermoelectric generator operating under constant heat flux conditions have been computed. Expressions for power output, optimum efficiency, and optimum ratio of internal‐to‐load resistance show that optimization requires operating conditions appreciably different from those for the operation of thermoelectric generators having constant hot and cold junction temperatures. Performance curves are presented for the optimum ratio of internal‐to‐load resistance when either the internal resistance or the load resistance is under the control of the designer.

ISSN:0021-8979    

DOI:10.1063/1.1735835

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The stress fields of an infinite and a finite screw dislocation wall are given and from them the interactions of the screw dislocation walls with parallel and nonparallel dislocations have been studied. The nature of the penetration through a screw dislocation wall of a number of parallel screw dislocations driven by external stress and the possible stress concentration for a pileup against the wall are discussed in detail. The forces exerted by a screw dislocation wall on nonparallel edge and screw dislocations are calculated. The significance of the local torques due to these forces as a possible mechanism for the screw dislocation wall to become a source for generating dislocations is pointed out. The metastability of the screw dislocation walls is demonstrated and their strain energy is estimated and compared with that of the edge dislocation walls. It is concluded that the resistance to penetration of a dislocation wall increases in the following order: infinite edge dislocation wall, finite edge dislocation wall, finite screw dislocation wall, and infinite screw dislocation wall. It is also found that the strength of a dislocation wall increases with its surface strain energy.

ISSN:0021-8979    

DOI:10.1063/1.1735836

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The technique of the total reflection of x rays has been applied to the study of thin films of Cu, Ni, Ge, and Se vacuum‐deposited onto polished glass substrates. Starting with fresh films, ``smooth'' enough to exhibit pronounced x‐ray interference fringes in the region just beyond the critical angle, the effects of vacuum anneal and oxidation were studied. Changes in the reflection curves are interpreted in terms of possible structural changes in the films. Reflection from layers of particles of carbon or polystyrene latex deposited onto ``smooth'' substrates was also studied for comparison.

ISSN:0021-8979    

DOI:10.1063/1.1735837

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The theory of phase oscillations in the synchrotron, first given by Bohm and Foldy, is extended to cover the case where the amplitude of the accelerating voltage is not constant and where the accelerated bunch is itself sufficiently large to produce an appreciable part of the accelerating voltage. It is found that the phase oscillation is more stable when the driving frequency is less than the natural frequency of the accelerating electrode system, and that the plate characteristic of the driving amplifier has a negligible effect on the phase stability.

ISSN:0021-8979    

DOI:10.1063/1.1735838

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Current noise measurements on the same lightly doped cadmium sulfide crystal having indium soldered contacts of different quality are used to demonstrate the strong influence of contacts on the observed noise spectra. The results suggest the presence of shallow trapping states distributed in energy and located near the electrodes. The concentration of these states depends on the quality of the contact. These effects are not contact noise in the usual sense since the shape of the noise spectra is only moderately affected; however, the noise level may change by orders of magnitude.

ISSN:0021-8979    

DOI:10.1063/1.1735839

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The solid‐liquid interface shape during growth from the melt has been determined for pure materials in the vicinity of external and internal surfaces; both the cases of isotropy and anisotropy of solid‐liquid interfacial energy have been considered. From these considerations it is possible to determine some effects associated with interface and external surface anisotropy. For example, a preferred direction of growth, a surface layer phenomenon and stray‐crystal formation during seeding and normal crystal growth may arise as a result of the solid‐liquid interface configuration.

ISSN:0021-8979    

DOI:10.1063/1.1735840

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A study was made at 4080 Mc of the partition noise introduced into a beam by a meshed grid as a function of its position along the beam. Simultaneous information concerning the beam dynamics was obtained by means of a beam analyzer. With cathode magnetic fields somewhat below those corresponding to immersed flow, the partition noise exhibited sharp dips as the grid in moving along the beam passed through the planes which corresponded to image planes of the cathode. These observations confirm the picture of noise smoothing taking place over relatively small areas in the vicinity of the cathode and elucidate the contribution of the random interception of electrons to the partition noise. With small cathode magnetic fields the partition noise varied sinusoidally with the cyclotron periodicity as the grid was moved along the beam. This variation with position is thought to result from the contribution to the partition noise of higher‐order mode conversion.

ISSN:0021-8979    

DOI:10.1063/1.1735841

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The linear thermal expansion coefficients of theaandcaxes of bismuth have been measured from 80°K to 540°K by mechanical means. These same coefficients were determined over a more limited range of temperatures by single crystal and powder x‐ray methods. The mechanical and x‐ray values did not differ significantly. The expansion coefficient for thecaxis was found to be 16.6±0.4×10−6(C°)−1at 100°K, 17.3±0.2×10−6(C°)−1at 150°K, and 17.6±0.2×10−6(C°)−1at 540°K. For theaaxis the expansion coefficient was 10.8±0.3×10−6(C°)−1at 100°K, 11.6±0.2×10−6(C°)−1at 150°K, and 11.8±0.2×10−6(C°)−1at 540°K.

ISSN:0021-8979    

DOI:10.1063/1.1735842

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The dislocation structure of type 6Hhexagonal silicon carbide has been studied by etching combined with optical microscopy and by x‐ray diffraction microscopy. The validity of the conventional etching technique for identification of the sites of the intersection of dislocations with (0001) surfaces has been established. However, high densities of dislocations lying in (0001) planes and hence heretofore undetected by etching techniques were often observed by diffraction microscopy. Dislocations with [112¯0] vectors have now been found with evidence for slip both on basal planes and on a ``puckered'' pyramidal plane. Pileups formed by slip and dislocation walls formed by climb were also observed. Silicon carbide shows many of the characteristics of more conventional plastically deformable materials.

ISSN:0021-8979    

DOI:10.1063/1.1735843

出版商:AIP    

年代:1960

数据来源: AIP