摘要:

Details are given about the preparation of suitable aluminum samples for studying the effects of electron irradiation of single crystals. The observed annealing spectra of stage I differ for samples irradiated along different crystallographic directions. Results show that when the atomic‐recoil energy is slightly greater than the threshold energy, the IBsubstage is enhanced for irradiations parallel to the ⟨100⟩ but is suppressed for the ⟨110⟩. Evidently, the most favorable conditions for producing IB‐type defects occur when the initial atomic displacements cause atoms to move in the ⟨100⟩. A qualitative discussion is given which explains the observed energy dependence of the single‐crystal samples in terms of atomic displacements along ⟨100⟩ and ⟨110⟩ directions.

ISSN:0021-8979    

DOI:10.1063/1.1657058

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The fracture of brittle coatings on a strained substrate is examined from two points of view. In the first case, the substrate deforms continuously and regularly spaced fractures occur in the coating. The spacingdat any strain &egr; is given by In &egr;/&egr;0= (4g/d) (1−d/d0), whered0, &egr;0are any convenient set of data points, andgis a parameter having the units of length. In the second case, the substrate deforms by crystallographic slip and fracture of the oxide may or may not occur at the slip step. The criteria for fracture are that the interface adhesive stresses be too large for the coating to sustain the necessary peel stress. Quantitative relations are given in terms of the coating thickness, fracture strain, and the orientation of the slip step with respect to the surface. The results for both cases are compared with experiment and found to be in essential agreement.

ISSN:0021-8979    

DOI:10.1063/1.1657059

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Mechanical polishing can generate a flowed lattice and minute crevices in silicon surfaces. Dislocations and stacking faults develop during high‐temperature annealing treatments. A systematic investigation of the fault has led to proposed mechanisms for stacking‐fault formation, growth, and annihilation. Fault nucleation appears to occur at pinning centers in the flowed lattice provided by crevices fixed by a thermally grown silicon dioxide film. Such pinning centers increase the probability of dislocations intersecting with one another. The intersection of two dislocations which satisfies the Lomar‐Cottrell conditions will form a stacking fault. The stacking faults which form in the above dynamic system are extrinsic, bound by ⅓ [111] Frank partials. Such faults grow by vacancy emission. Enhanced fault growth is provided by the dynamic recovering lattice. Fault annihilation can occur if the vacancies emitted by the enhanced fault growth are not annihilated. The Si&sngbnd;SiO2interface appears to be the dominant vacancy sink during the period of rapid oxide growth.

ISSN:0021-8979    

DOI:10.1063/1.1657061

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The dispersion relation is derived for a finite length one‐dimensional electron beam neutralized by positive ions with zero electron and ion temperatures. Contrary to previously published results it is shown that finite ion mass does not produce stability. There are two modes of instability, electron space‐charge waves and ion oscillations. Their relative importance at different lengths is considered.

ISSN:0021-8979    

DOI:10.1063/1.1657062

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The formation of striations in a normal glow discharge has been correlated with a relaxation‐type phenomenon occurring at the cathode dark space‐negative‐glow interface and caused by cathode instabilities. A beamlike stream of electrons, in excess of that number necessary to maintain the normal glow brought about by cathode instabilities, is postulated to cross the cathode‐fall region and to interact with neutrals in the negative glow causing a surplus of positive ions at the interface between the cathode dark space and the negative glow. This group of positive ions constitutes a positive striation which in turn is accelerated toward the cathode. The experimentally observed times for these striations to cross the cathode‐fall region give a velocity of approximately 104cm/sec, which is in good agreement with other observations of positiveions striation velocities.

ISSN:0021-8979    

DOI:10.1063/1.1657063

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A brief description is presented of various ways in which mixed absorption‐dispersion modes can arise. Exact closed‐form solutions are derived for the line parameters of zeroth derivatives of Lorentz shape functions containing arbitrary linear mixtures of absorption and dispersion. The parameters are obtained as functions of &egr;, where &egr; represents the fractional admixture of one signal component relative to the other, and may be determined experimentally from the signal‐amplitude asymmetry. Very simple expressions are also derived for the mixed first derivative curves if terms of the order of &egr;3and higher are neglected. In the case of the 1:1 admixture, this procedure introduces an uncertainty in the position of the line center of approximately 1% of the half‐width of the pure absorption curve. The implications of this analysis for practical spectroscopic measurements are discussed. In particular, a very simple relationship is shown to exist between the degree of admixture and the experimental variables.

ISSN:0021-8979    

DOI:10.1063/1.1657064

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The nonlinear polarizations which lead to mode‐locking in solid‐state lasers are examined under the realistic assumption that many modes oscillate. When all possible contributions to these polarizations are included in an estimate of their strength, it is found that self‐locking is to be expected in pulsed ruby and Nd‐glass lasers, and in Q‐switched ruby, Nd‐glass, and Nd&sngbnd;YAG lasers. In particular, we find that the strengths of the various locking terms increase with the total energy in all the oscillating modes and also with decreasing mode spacing. The total number of modes into which the energy is distributed influences the locking range weakly through a term logarithmic in this number. Experimental evidence in support of these conclusions is also presented.

ISSN:0021-8979    

DOI:10.1063/1.1657065

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Guided motion of vortices in type‐II superconductors is studied by measuring transverse voltages. The experiments were performed mainly on a Nb&sngbnd;Ta alloy for various magnetic fields, transport currents, and temperatures. The experiments show that in general, the onset of apparent resistance in the mixed state is coupled with fully guided motion of the vortices. With increasing magnetic field, the ratio of transverse and longitudinal voltages decreases. However, this ratio goes through a maximum in materials where the apparent resistivity goes through a minimum. A model is discussed with a guiding force becoming independent of current at higher current densities. The voltages calculated with this model are in agreement with those measured on a Nb&sngbnd;Ta alloy and on a Pb&sngbnd;In alloy. The model is also applied to the situation where a true Hall effect is measured. The conclusion is that pinning and guiding can reduce the Hall angle when the current density is small. The large Hall angles measured in the mixed state cannot be related to guided motion with the existing models of flux flow.

ISSN:0021-8979    

DOI:10.1063/1.1657066

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Growth of hillocks has been observed during annealing of sputtered Au films. The height of a hillock is proportional to the area it occupies in the film. This empirical relationship has been used in a model which postulates that hillock growth is associated with stress relief in the Au. The model is able to relate the sign and magnitude of the stress with hillock size and density. The general character of the growth kinetics is also predicted by the model.

ISSN:0021-8979    

DOI:10.1063/1.1657067

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Dislocation channels cleared of radiation‐produced defect clusters were observed by transmission electron microscopy in polycrystalline niobium irradiated to 4×1018neutrons/cm2(E>1 MeV) and then deformed in tension to 6.6% strain. From electron diffraction patterns and diffraction contrast (g·b) analysis, the {110} plane was determined to be the plane on which the dislocation channels formed in most cases. The strain due to the motion of slip dislocations in the channels was deduced from the offset at intersections between the channels and other microstructural features. The strain corresponded to the passage of 1–3 slip dislocations per slip plane. Several mechanisms for the clearing of defect clusters by slip dislocations are discussed. These include: annealing due to the heat of plastic deformation, chopping up or sweeping up of defect clusters by slip dislocations, and annihilation by antidefects.

ISSN:0021-8979    

DOI:10.1063/1.1657068

出版商:AIP    

年代:1969

数据来源: AIP