摘要:

Dislocation etch pits can be formed on LiF by a dilute aqueous solution of FeF3. In this report the etch pit formation is described in detail, and the mechanism for pit formation is discussed. The nature of the etch pits depends on the character of the dislocation, and on the exact composition of the etchant. Edge dislocations and screw dislocations etch slightly differently; the former produce deeper pits. The etching is inhibited by some segregated impurities at dislocations, therefore aged dislocations and fresh dislocations etch much differently. Etch pit formation is probably due to the preferential nucleation of unit pits one molecule deep at a dislocation, and the movement of the monomolecular steps across the surface. The relative rates of these two processes determine the shape of the etch pits. The nucleation rate for unit pits depends upon the dislocation energy, hence upon the character of the dislocation and the impurity content as suggested by Cabrera. The nucleation rate is faster at edge dislocations, because of their higher energy. The nucleate rate is low at dislocations with segregated impurities, because the impurities lower the dislocation energy. The ferric ion is adsorbed on the surface and inhibits the motion of steps, so that steeper, more visible pits are produced as the iron content is increased.

ISSN:0021-8979    

DOI:10.1063/1.1723277

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Polished and etched, as well as free surfaces, of barium titanate were studied by the direct carbon replica technique. Domain configurations of both the 90° and 180° type were made visible at a higher magnification than has been possible by optical methods. The behavior of 90° domains at a grain boundary was studied and photographed. Hexagonal and square growth patterns of the free surface were observed and photographed.

ISSN:0021-8979    

DOI:10.1063/1.1723278

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The results of a numerical treatment of the dependence of half‐widths of electron energy distribution on temperature, field, and work function are presented for the electrons emitted from a metal at temperatures and fields within the extended field emission range. For the distribution, the width of the peak at half maximum and the partial widths from peak to half‐maximum on either side are presented graphically as a function of one parameter depending on temperature, field, and work function. The peak energy can also be determined in terms of this parameter.

ISSN:0021-8979    

DOI:10.1063/1.1723279

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

It has been demonstrated that dislocations can be revealed as etch pits in copper crystals doped with a small amount of Te. The progress of polygonization of such copper after bending was followed with etch pits and x‐ray diffraction. It was found that climbing occurred at 500°C and that polygonization was complete after 2 hr at 1000°C. In similar experiments with three samples of nominally 99.999% copper, the one which was probably purest did not polygonize, while the other two did so. This indicates that if impurity is necessary for polygonization, only a very small amount is required.

ISSN:0021-8979    

DOI:10.1063/1.1723280

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Infrared radiation has been used to obtain a direct measure of the added carrier concentrations immediately adjacent to a junction when a current was passing through it. The currentversuscarrier density characteristics thus determined can provide sensitive tests of junction theory. For junctions between two highly doped germanium regions and low injection levels, the experimental results agree with existing theory. For these junctions and high injection levels, or for junctions between regions where one or both sides may be lightly doped and for arbitrary levels of injection, it is necessary to extend the theory. This is done by extending the boundary conditions for higher levels of injection and using the current equations in the ambipolar form, where the field as well as the diffusion currents are considered. The resulting currentversuscarrier density relationship involves the total current and takes into account, for both sides of the junction, the change in conductivity with injection level and the change in the drift length with the applied electric field. If, in addition, the change in lifetime with injection level is taken into consideration, good agreement obtains between experiment and theory. Current‐voltage relationships are also derived which contain the above mentioned improvements.

ISSN:0021-8979    

DOI:10.1063/1.1723281

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Cleaved germanium surfaces, oxygenated at room temperature, were heated under high vacuum and the restoration of their oxygen‐adsorbing capacity was determined. No restoration was observed at 425°C. Above 575°C, however, the oxygen‐adsorbing capacity of the surfaces was completely recovered. Discharge of GeO from the surface was associated with this process. The restoration process followed first‐order reaction kinetics with an activation energy of 56 kcal/mole. Concurrently with restoration a pronounced decrease in the surface area was observed. The results are discussed in terms of the kinetic and energy requirements of the system.

ISSN:0021-8979    

DOI:10.1063/1.1723282

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

This paper describes a 4.3‐mm radiometer and measurements made with it of the apparent temperature of various terrestrial materials, the attenuation through the atmosphere and the temperature of the sun. Materials whose apparent temperatures were measured included water, wood, metal, grass, asphalt, gravel and asbestos. Since their apparent temperatures are dependent upon their reflectivity, these data are interpreted in terms of the background reflected by the materials.The attenuation vertically through a clear sky ranged between 1.6 and 2.3 db. The sun, of optical disk size, was found to be between 104and 1.2×104°K on May 3 and June 17, 1957.

ISSN:0021-8979    

DOI:10.1063/1.1723283

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The noise temperature, band width, and gain modulation characteristics of a transmission maser are obtained as a function of iris coupling for fixed desired gain and other parameters. It is found with the help of a characteristic curve that certain of these characteristics can be optimized at the expense of others. The same functions are compared in the case of a reflection maser. The reflection maser is shown to be superior in most respects, although the same noise temperature may be attained with the transmission maser at a substantial sacrifice in band width and gain modulation. The reflection maser is also limited by the availability of good circulators, while a transmission maser can be made independent of load. A figure of merit for both types of maser amplifiers is obtained. This isQ0Z, whereQ0is the unloaded cavityQ;Zis given byZ=4&pgr;&xgr;&khgr;0−Q0−1; &xgr; is the filling factor; and &khgr;0is the negative rf susceptibility. When the cavity band width is much less than the susceptibility band width, an auxilliary figure of merit isZ.

ISSN:0021-8979    

DOI:10.1063/1.1723284

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The equivalent shunt impedance of a lightly coupled transmission cavity can be measured by inserting very small perturbing elements and using a simple bridge method to detect small shifts of transmission phase. A simple graphical procedure is developed for the interpretation of these measurements. It is shown that the procedure measures directly the shunt impedanceRof the cavity, rather than the geometric quantityR/Q. Experimental results are presented for one such cavity, which show that phase information thus obtained is about 100 times as sensitive as amplitude information normally obtained from a transmission cavity.

ISSN:0021-8979    

DOI:10.1063/1.1723285

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Orthogonality relations are given for the ``four‐vector'' guided modes of anisotropic uniform wave guides and for the ``six‐vector'' guided modes of uniform wave guides containing unidirectional electron beams with axially independent dc velocities. In general, these orthogonality relations involve both the modes of the given wave guide and those of an appropriate ``adjoint'' wave guide. A description is given for the adjoint wave guides associated with wave guides which contain media whose characteristics are restricted only by the requirement that they be axially independent and which, if bounded, are subject to a variety of boundary conditions arising from idealizations of actual boundaries.

ISSN:0021-8979    

DOI:10.1063/1.1723286

出版商:AIP    

年代:1958

数据来源: AIP