摘要:

Ignition of a thermionic cathode discharge in mercury vapor at the low applied potential of 2.4 V is shown to be the result of a potential minimum in space 0.8 V below the cathode, and of a favorable contact potential difference. Good emitters require more voltage to fire than high work function cathodes. Using an argon buffer gas at about 3.5 mm Hg pressure, ignition is easiest with an added Hg vapor pressure of 1.85 mm. Adequate pressure is required because of the two‐stage ionization which produces ignition. This process applies also to the noble gases, and requires that ignition cannot occur with electron energy less than half the ionization potential.

ISSN:0021-8979    

DOI:10.1063/1.1702539

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The average velocities of dislocations have been measured in four semiconductor crystals‐silicon, germanium, gallium antimonide, and indium antimonide. The range of measured velocities was between 10−6and 2×10−1cm/sec. The dislocation velocities in these crystals are relatively insensitive to stress when compared to LiF or Si‐Fe. The effect of temperature, in the range 0.5 to 0.8TM, on the velocities at various constant stresses was measured and the activation energies for the dislocation velocities were obtained in each of the crystals. No marked dependence of activation energy as a function of the applied stress was obtained.The effect of strain on the dislocation densities was measured as a function of orientation, temperature, and strain rate. It was found that even in initially dislocation‐free crystals, dislocations were generated at quite low stresses. From direct measurements of etch pits and dislocation velocities it was possible to estimate the fraction of mobile dislocations. Under certain conditions the percentage of mobile dislocations was as low as 3 to 8%.

ISSN:0021-8979    

DOI:10.1063/1.1702540

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Based on the theory of anisotropic elasticity, the stress field of a single dislocation, the force between two parallel dislocations, and the stress field of various types of infinite dislocation walls and arrays are fully analyzed for a hexagonal crystal.The attraction sector of an edge dislocation with respect to another edge dislocation of the same sign is no longer the half‐quadrant as in the isotropic case. For graphite crystals the attraction sector is about 70° instead of 45°.The force between two parallel screw dislocations is not central. A tangential component exists, being zero alongxandyaxes. The tangential force will retard the formation of screw dislocation arrays along any plane except those parallel or normal to the basal plane. Cross slip may be aided or opposed by this force, depending on the direction of applied stress.The stress field of an infinite dislocation wall or array, either parallel or normal to the basal plane, has similar characteristics to those from isotropic treatment, although their magnitudes and geometries may differ considerably.Numerical data of six important material constants are tabulated for many common hexagonal crystals.

ISSN:0021-8979    

DOI:10.1063/1.1702541

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The temperature variation of the saturation magnetization of a &ggr;‐ferric oxide sample has been interpreted by use of Ne´el's molecular‐field model, with neglect ofA‐AandB‐Binteractions. The parameters assumed are:jof the Brillouin function=52; a net moment of 1.25 Bohr magnetons per iron atom; ratio of the number of atoms onAsites to the number onBsites, 8/(40/3)=3/5. From these parameters the functionM/M∞=G(T/&thgr;) was calculated numerically;M=magnetization at temperatureT, M∞=magnetization atT=0, &thgr;=Curie temperature. The data fit the theoretical curve very well if &thgr; is assigned the value 1020°K.

ISSN:0021-8979    

DOI:10.1063/1.1702542

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The Schiff small‐angle approximation for plane‐wave scattering by a dielectric is integrated over an appropriate angular distribution of incident plane waves in order to represent finite‐beam scattering. The intensity distribution near the forward direction where incident and scattered waves interfere can now be expressed in a meaningful way. If the radius of the incident beam is not large relative to the dimensions of the scattering system, the scattered wave is seriously modified. A simple definition of cross section is chosen, and an extended optical theorem for total cross sections is derived.

ISSN:0021-8979    

DOI:10.1063/1.1702543

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An experimental technique for the direct observation of imperfections in single crystals is described. It is based on the anomalous transmission effect of x rays observed in crystals of high perfection. The parallel beam method previously used only for the mapping of dislocations has been improved so that large area x‐ray topographs are recorded. It can now be applied to the detection of impurities, segregation, and precipitation effects in semiconductor materials. Microsegregation of oxygen in silicon, precipitation of copper in silicon, and arsenic segregation in germanium were used to study the influence of segregation and precipitation on the anomalous transmission. Working conditions of x‐ray diffraction microscopy are discussed, and it is shown that segregation phenomena produce typical impurity contrast which is reflection‐dependent if the impurities are in solid solution. For precipitated impurities, this relation does not exist.

ISSN:0021-8979    

DOI:10.1063/1.1702544

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The internal friction peak for nitrogen in dilute solutions in very pure chromium occurs at 160°C for ∼1 cps but is unstable due to partial precipitation of nitrogen. Interpretation of internal friction data at low frequencies and elastic aftereffect measurements in terms of the theory of Snoek gives the lattice diffusion rate of nitrogen in chromium asD=3×10−4exp (−24 300/RT).

ISSN:0021-8979    

DOI:10.1063/1.1702545

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Seven compositions were prepared in the system As2Te3‐Tl2Te‐As2Se3. Some of the samples were amorphous while others were diphasal including both amorphous and crystalline phases. The electrical and thermal properties of the samples were structure dependent. At room temperature the resistivity values ranged from 4.7×10−3to 1.8×105&OHgr;‐cm, Seebeck coefficient values were 40 to 1210 &mgr;V/°K and thermal conductivity values were 18.1 to 2.2 mW/cm‐deg.

ISSN:0021-8979    

DOI:10.1063/1.1702546

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

When total internal reflection of light occurs, radiation penetrates beyond the reflecting surface into the rarer medium where the intensity decreases with distance from the interface in an exponential manner. Since the degree of coupling to this radiation can be controlled by adjusting the proximity of another object to this interface, it is possible to utilize this phenomenon in the measurement of film thickness and to obtain high contrast images of surface reliefs.

ISSN:0021-8979    

DOI:10.1063/1.1702547

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The quenched‐in resistivity in gold was measured for cooling rates from 104to 105°C/sec. The quenched‐in resistivity increases considerably with increasing cooling rate and depends strongly on the quenching temperature over much of the range investigated; for example, for a cooling rate of 20 000°C/sec about 12% of the residual resistivity recovers during the quenching process for a quench from 700°C and about 20% recovers for a quench from 800°C. For the lower quenching temperatures the quenched‐in resistivity appears to approach saturation at the fastest quenching rates obtained. A linear relation between the logarithm of quenched‐in resistivity and the reciprocal of quenching rate was observed. This allowed linear extrapolation to infinite quenching rate. The quenched‐in resistivity &rgr;∞obtained by extrapolating to infinite rate, is expressed by &rgr;∞=&rgr;0exp(−Hf/kT), where &rgr;0=5.0×10−4&OHgr;‐cm and the formation enthalpy,Hf=0.97 eV. Assuming &rgr;∞corresponds to single vacancies rather than clusters, measurements of the length change of the quenched specimens and using Tewordt's result that a vacancy has 0.47 atomic volume, the following constants were obtained: The resistivity of 1 at. % of vacancies, 1.7×10−6&OHgr;‐cm; the entropy of formation of a vacancy, 0.95×10−4eV/°K; and the fractional concentration at the melting point, 6.4×10−4.

ISSN:0021-8979    

DOI:10.1063/1.1702548

出版商:AIP    

年代:1962

数据来源: AIP