摘要:

Anomalous galvanomagnetic effects associated with spatial discontinuities in carrier concentration have been observed inn‐type InSb. These discontinuities result from anisotropic segregation of impurities during crystal growth. An increase in the magnitude of the Hall coefficient at 20 000 gauss to nearly twice the weakfield value was observed in one case. The magnetoresistance is especially sensitive to inhomogeneities. For an inhomogeneous sample at a particular magnetic field, the measured &Dgr;&rgr;/&rgr;0may be as much as 100 times larger than that for a homogeneous sample. Negative magnetoresistance has also been observed at room temperature in inhomogeneous samples. All of the above observations are predicted qualitatively by considering a simple model consisting of a long, thin specimen having a discontinuity in resistivity and Hall coefficient in the current direction. The boundary value problem corresponding to this case is solved to predict the electric field and current densities.

ISSN:0021-8979    

DOI:10.1063/1.1736110

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

When a wave of wavelength &lgr; is incident upon an opaque object of typical dimensiona, a shadow is formed in the geometric optics limit &lgr;/a=0. If &lgr;/ais small and not zero, the shadow boundary is shifted slightly from the geometrical shadow boundary as was first shown by Artmann. He found the shift to be asymptotic to &agr;(&lgr;2a)⅓for a circular cylinder, where &agr; is positive or negative according as the field or its normal derivative vanishes on the cylinder. The same result was obtained by Rice for a parabolic cylinder, but for the hard cylinder his &agr; differed from Artmann's. We have redetermined &agr; for the circular cylinder and found it to agree with the result for the parabolic cylinder in both cases. We have also determined the shift for a circular cylinder on which the field satisfies an impedance boundary condition. The former result is implicit in the work of Goriainov and both results are implicit in the work of Wait and Conda. We have also determined the scattering cross section of a circular cylinder with an impedance boundary condition. These results lead us to propose two formulas, one for the shift of the shadow boundary and one for the scattering cross section, of any smooth two‐ or three‐dimensional object. The latter expresses the deviation from the geometrical optics cross section as an integral, around a normal section of the shadow, of a multiple of the shift. This formula is verified for a sphere and for oblique incidence on a circular cylinder. Both electromagnetic and scalar waves are considered.

ISSN:0021-8979    

DOI:10.1063/1.1736111

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A new method of generating a stable plasma at atmospheric pressure using inductive coupling at a frequency of several Mc is described. Methods of starting and operating this plasma in argon, and mixtures of argon with helium, hydrogen, oxygen, and air are discussed. The Fowler and Milne method was used to measure the temperature profile of the plasma under various conditions of gas flow and composition, and at several power levels. Measured peak temperatures ranged from 14 000°–19 000°K. The power losses from the plasma in the form of convection, radiation, and conduction to the nozzle walls were measured under the same conditions. Total power transferred to the plasma ranged from 1.6–3.1 kw which was approximately 50% of the input power. The extent to which local thermal equilibrium prevails in the plasma is discussed; the available evidence indicates that under the operating conditions described herein, equilibrium is closely approached.

ISSN:0021-8979    

DOI:10.1063/1.1736112

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A survey of the salts of the rare‐earth series shows that anhydrous PrCl3has energy levels and selection rules suitable for use in a solid state infrared quantum counter as proposed by Bloembergen [N. Bloembergen, Phys. Rev. Letters2, 84 (1959)]. Two suitable schemes are proposed, one for detection at 2.33 &mgr; and a second for detection at 104 &mgr;. Consideration is given to isolation of the final detector from the pumping signal and a suitable experimental arrangement for unambiguously determining proper operation is shown.

ISSN:0021-8979    

DOI:10.1063/1.1736113

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Copper single crystals subjected to a neutron dose of 3×1018nvt (total flux) at pile temperature have been examined after deformation by the following experimental techniques: (a) observation of the load‐extension relationships, (b) investigation of the slip‐line structure with the electron microscope, and (c) diffraction electron microscopy of thinned‐down single crystals before and after deformation. The critical resolved yield stress is in the order of 1.6 kg/mm2. In the early stages of deformation, the load‐extension curves show serrations which are as large as 1.0% of the critical resolved shear stress. In the linear portion of the stress‐strain curve, the rate of work hardening is less for irradiated single crystals than for the nonirradiated. The stress‐strain curves of the irradiated and the nonirradiated specimens are similar in the parabolic region of the curves. The slip‐line structure, at low deformations, consists of fine slip lines that are clustered together; the distances between the slip lines are, on the average, 100 A and often less; the distances between the clusters are in the order of 4&mgr;. This structure is quite different than the alpha‐brass structure, which in the past had been considered typical for irradiated copper. Cross slip, which is most abundant in the linear hardening region of the stress‐strain curve, is found to be orientation dependent. The slip‐line structures for the irradiated and nonirradiated crystals at high strains are very similar. Prismatic dislocation loops, apparently resulting from the condensation of vacancies, are found to be the most frequently produced radiation defect. The interaction between loops and glide dislocations results in heavily kinked dislocations which are probably responsible for the observed high yield stress. The glide dislocations were seen to remove the radiation damage. Because of this cleaning out of radiation‐produced defects and the ability of the dislocations to multiply from new sources, the prolonged ``easy glide range'' can be explained. Further, the proposed mechanism provides an explanation of the work hardening in the linear and parabolic parts of the stress‐strain curve.

ISSN:0021-8979    

DOI:10.1063/1.1736114

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Self‐diffusion of Ag110in silver polycrystals subjected to simultaneous torsion was studied near 700° and 800°C using the sectioning technique. Strains ⩽ 0.50 and strain rates ⩽ 13.8×10−5sec−1were employed. Specimen structures before and after deformation were also examined. The effects of straining on diffusion were relatively small in all cases. At 800°C the diffusivity was increased by no more than ∼50%. At 700°C the increase was no more than ∼100%. A substantial part of this observed enhancement was undoubtedly only apparent and due to difficulties associated with surface roughness. The results agreed generally with our previous work involving deformation in extension and compression but were in marked disagreement with recent results of Lee and Maddin and Forestieri and Girifalco [C. H. Lee and R. Maddin, Trans. AIME215, 397 (1959); A. F. Forestieri and L. A. Girifalco, J. Phys. Chem. Solids10, 99 (1959)], who have reported enhancements larger by one to two orders of magnitude. No simple explanation for these differences was found. Estimates of dislocation short‐circuiting and the generation of extra point defects indicated that only small enhancements should be expected in agreement with the present results.

ISSN:0021-8979    

DOI:10.1063/1.1736115

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Measurements of the junction characteristics and the transport properties on either side of a vacuum‐cleaned siliconp‐njunction have been carried out. The changes in these properties during the adsorption of oxygen and hydrogen have also been investigated. In the clean condition, the value of (EF−EV) for both 21.5 ohm‐cmntype and 27 ohm‐cmptype was found to be 0.13–0.14 ev. When the silicon surface was clean, a large excess current across the junction was observed which disappeared during the adsorption of gas.

ISSN:0021-8979    

DOI:10.1063/1.1736116

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Distribution coefficients of several column 2, 4, and 6 elements in GaSb are reported, and some of the physical properties of this material are discussed briefly.

ISSN:0021-8979    

DOI:10.1063/1.1736117

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

First magnetocrystalline anisotropy constantsK1∞of 3.6, 6.7, 8.8, and 12.4 wt% silicon in iron alloys have been measured at 77°K and 297°K by determining the torque exerted on {100} single‐crystal disks in uniform magnetic fields. The following results on disordered alloys have been obtained:Composition (wt%Si)Temperature (∘K)K1∞×103(erg cm−3)3.677430±10297360±106.777290±10297205±108.877245±10297165±1012.477120±529778±5The measurements of this investigation are compared with the previously known studies. The agreement, where an overlap occurs, is satisfactory.

ISSN:0021-8979    

DOI:10.1063/1.1736118

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Techniques have been developed that will permit a unique determination of an absorption coefficient &dgr;afor 0.2‐ to 20‐ev electrons on cleaved, insulating crystals. Two classes of electron trapping levels, one that empties rapidly and one that does not empty at room temperature, may exist in the target and if they do, effects caused by them may perturb the data. Experimental techniques were developed to compensate for each characteristic effect. Pure and nonstoichiometric KBr and KCl crystals were studied. The probability that a crystal‐incident electron results in a charge influx was found to vary makedly as a function of the impact energy and in a manner characteristic of the target. This feasibility study indicates that slow electron beams could be a powerful tool for diagnosing surface and bulk properties of insulating crystals.

ISSN:0021-8979    

DOI:10.1063/1.1736119

出版商:AIP    

年代:1961

数据来源: AIP