摘要:

Experimental measurements are reported of the effect of mechanical stress on minority‐carrier lifetime in germanium and silicon. Lifetime has been measured as a function of temperature and for stress in the ⟨111⟩, ⟨100⟩, and ⟨011⟩ directions at stress levels up to 1010dyn/cm2. The lifetime changes were found to be reversible, and changes in lifetime of as much as a factor of 3 were observed at stress levels of 1010dyn/cm2. For all samples investigated, lifetime was observed to increase inn‐type material and to decrease inp‐type material. A theoretical model has been developed for explaining the effects of mechanical stress on minority‐carrier lifetime in germanium and silicon. The model is an extension of the Shockley‐Read model to account for stress‐induced splitting of the conduction and valence bands plus a possible shift in energy of recombination levels with stress.

ISSN:0021-8979    

DOI:10.1063/1.1659449

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This paper reports recent measurements of the shock piezoresistance coefficient of manganin (in wire and thin‐foil geometries) in high‐density polycrystalline alumina (Lucalox). For manganin in a wire geometry and for shock stresses below the Hugoniot elastic limit (HEL) of Lucalox, this coefficient was found to be much higher in Lucalox than in C‐7 epoxy, Hi‐D glass, and soda‐lime glass. The cause of the higher coefficient is postulated as the production of lattice defects in the manganin wire arising from large plastic deformation of the wire at compressive stresses below the HEL of Lucalox. For stresses above the HEL of Lucalox, the shock piezoresistance coefficient of manganin wire in Lucalox agrees quite well with that of manganin wire in other insulators. In a thin‐foil geometry in Lucalox, the coefficient was found to remain constant above and below the HEL of Lucalox.

ISSN:0021-8979    

DOI:10.1063/1.1659450

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The reflection of light at grazing incidence from a shock wave at Mach No. 1.94 in air at atmospheric pressure is measured. It is found that the reflection coefficient is equal to that calculated when second‐order effects are included. From the variation of the reflectivity across the front it is found that the shock has a curvature of 5.4±0.4 m, a tilt of less than ±⅕, and distortion amplitude of less than 3×10−3cm.

ISSN:0021-8979    

DOI:10.1063/1.1659451

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Single‐crystal specimens (7‐ and 12‐mm thick) of sodium chloride were impacted with flat‐nosed, gas‐driven projectiles, and the Hugoniot elastic limit (HEL) was determined by reducing quartz gauge measurements. The HEL for the [100], [110], and [111] crystal directions was 0.26, 0.77, and 7.4 kbar, respectively. Stress—time profiles for specimens shocked in the [100] and [111] direction show evidence of stress relaxation behind the elastic precursor. This phenomenon is more pronounced in 12‐mm‐thick specimens. The ratio of the resolved shear stress on the active slip systems for uniaxial strain (shock loading) conditions to that for uniaxial stress (static loading) indicates a strain‐rate effect. This ratio increases from 3.1 for loading in the [100] direction to 8 for the [110] direction and to 21 for the [111] direction. The anisotropy of the HEL with crystal direction is related to the resolved shear stress on the primary and secondary slip systems in single‐crystal sodium chloride. The large HEL for shock loading in the [111] direction is a consequence of the resolved shear stress on the primary slip systems being zero. Thus, for deformation by slip to occur, a secondary slip system (or systems) must be activated which will require a higher resolved shear stress. The experimental data for single crystals of copper and beryllium can also be explained in terms of the resolved shear stress.

ISSN:0021-8979    

DOI:10.1063/1.1659452

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Several experimental techniques of measuring the nonradiative transition probabilities in condensed media are briefly reviewed and the fluorescence rise‐curve technique is analyzed in detail from the theoretical and practical points of view. Some applications and experimental pitfalls are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1659453

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An analysis of the infrared‐interference method of measuring epitaxial layer thickness is given which shows that the technique is useful for measurement of layers thinner than one micron. The connection between plasma resonance and infrared interference is established. A new method of interpreting the infrared spectra is given which produces both the layer thickness and substrate impurity concentration.

ISSN:0021-8979    

DOI:10.1063/1.1659454

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The damage introduced by electrical discharge machining was investigated in low‐dislocation copper single crystals with a view toward determining the acceptability of the technique for the preparation of nearly perfect crystals. The damage was observed by anomalous x‐ray transmission, etch‐pitting, and x‐ray rocking curve halfwidths. It was concluded that with due care this technique could be used successfully, even for relatively soft crystals.

ISSN:0021-8979    

DOI:10.1063/1.1659455

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1659456

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1659457

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1659458

出版商:AIP    

年代:1970

数据来源: AIP