摘要:

Because line‐patterned &egr;‐phase Pb‐Bi films are used as the counterelectrode materials of Pb‐alloy Josephson junction integrated circuits presently under investigation, a study was undertaken on the effects of the film width on the strain distribution and average elastic strain supported by the film at 4.2 K. The study was carried out using an x‐ray diffraction technique for 0.6‐&mgr;m‐thick Pb‐29% Bi films that were deposited onto oxidized Si wafers at 273 K, and then cooled to 4.2 K. The blanket films supported almost all of the strain elastically at 4.2 K, and symmetric x‐ray diffraction peak profiles were observed in the films, indicating that they were uniformly strained. Asymmetric peak profiles due to nonuniform strain distributions in the film were observed when the film width was smaller than ∼40 &mgr;m. The measured x‐ray diffraction peak profiles were analyzed using a computer simulation technique. The analysis indicated that the strain distribution at the center of the film is close to the one calculated using the energy minimization method developed by Aleck. Average strains supported elastically at 4.2 K by the films were observed to decrease with decreasing the film widths as predicted by the model, and excellent agreement was obtained between the measured and calculated average strains in the films with various film widths. However, the high local strain at the film edges predicted by this model is not observed. The strain is believed to relax during cooling to 4.2 K.

ISSN:0021-8979    

DOI:10.1063/1.331135

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We have used a ’’reverse gun’’ that fires a ceramic plate at a preheated metal target to study the dependence of flow stress on temperature. Impact velocity versusLf /L0isotherms have been determined for Al, two types of Cu, 4340 steel, and Ta at 295, 730, and 1235 K, and for U at 295 and 725 K. A modified Steinberg–Guinan constitutive model and a Gru¨neisen equation of state were used to obtain hydrodynamic code simulations of the deformation process. A strong temperature dependence of the length ratio was clearly evident for all materials.

ISSN:0021-8979    

DOI:10.1063/1.331136

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We introduce a method, which is free of specimen edge effect, for the determination of critical stress in material brittle fracture. Using this method, we have investigated the critical stress in silicon brittle fracture. Silicon wafers polished with silica gel showed an average fracture stress of 2.8 GPa, with a standard deviation of 1.2 GPa and a maximum observed value of 6.9 GPa. We have also investigated effects of various surface treatments on the critical stress. Mechanically lapped surfaces, with damage penetrating deeper than ∼3 &mgr;m, reduced the fracture strength to 0.3–0.4 GPa (damage surface placed in tension). Both polysilicon and quartz overlays reduced the silicon fracture strength only very slightly, while argon implantation (at 150 keV, with a dose of 1×1016cm−2) did not show a detectable effect. However, anneal of the argon implanted samples at 900 °C in nitrogen for one hour significantly increased the silicon fracture strength, conceivably as a consequence of the removal of existing surface flaws by an epitaxial regrowth of the implantation‐amorphized surface layer. The last finding is both of basic interest and of practical significance. Silicon wafers of (100) orientation showed a ∼50% higher fracture strength than wafers of (111) orientation.

ISSN:0021-8979    

DOI:10.1063/1.331137

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The scattering of sound waves by isolated inhomogeneities in a solid is examined using the Born approximation. A procedure is developed to extract information about the effective volume and shape of the scatterer. The procedure uses data from the long‐wavelength region where this approximation is valid. The volume and shape information is in the form of special moments of the volume of the scatterer which depend on the orientation of the scatterer relative to the direction of the difference in the incoming and outgoing wave vectors. A scheme is described which permits the characterization of the scatterer in terms of an equivalent ellipsoid. The scheme provides a second‐moment solution of the inverse scattering problem.

ISSN:0021-8979    

DOI:10.1063/1.331138

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The dependence of the high‐temperature internal friction of germanium and silicon, both intrinsic and highlyntype, was measured as a function of temperature, frequency, dislocation density, and dopant concentration. An acoustoelectric peak in both germanium and silicon was detected and found to agree well with the theory of Weinreich. The high‐temperature dislocation‐dependent damping in intrinsic germanium and silicon was studied and seen to be consistent with most previous studies. If deformed at high temperature and allowed to anneal, highly dopedn‐type material behaved intrinsically due to preferential precipitation at dislocations; however, if deformed at moderate temperatures and not allowed to anneal, such crystals exhibited a greatly enhanced dislocation‐dependent internal friction which depended on the extrinsic carrier concentration. A theory was developed for dislocation damping in semiconductors and was found to agree well with experimental results. The model is based upon electronic viscous damping of dislocations by excess current carriers whose lifetimes are controlled by Auger recombination processes.

ISSN:0021-8979    

DOI:10.1063/1.331139

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Magnesium doped single‐crystal LiF was shocked above the critical shear stress necessary for rapid precursor decay. Post‐shock analysis of the samples indicate that the dislocation density in the shock front is not significantly greater than the preshot value.

ISSN:0021-8979    

DOI:10.1063/1.331140

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Using the shear cell technique the diffusion coefficientDAuof195Au in liquid Au0.81Si0.19has been measured in the temperature range 663–1773 K. The experimental values are compared with an estimation ofDmade in the framework of the Enskog approximation. The relative enhancement ofDAubelow 1100 K is attributed to short‐range order effects in the liquid.

ISSN:0021-8979    

DOI:10.1063/1.331141

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Grain‐boundary diffusivities of a Sn119radioactive tracer have been measured in polycrystalline Pb specimens in the temperature range 70–200 °C. The combined diffusion parameter &dgr;Dbis expressed by the Arrhenius relation &dgr;Db= 7.3×10−9exp(−0.41±0.02 eV/kT) (cm3/sec). The Sn impurity diffusivities are larger than Pb self‐diffusivities in the grain boundaries, which has been confirmed by codiffusion measurements of the two species. The lattice diffusivities reported in the literature for the Sn and Pb tracers also show a similar trend. In both situations the effect appears to be related to the physical characteristics of the two diffusing species.

ISSN:0021-8979    

DOI:10.1063/1.331142

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Synthetic crystals of layered titanium silver were grown epitaxially by vapor deposition techniques. The motivation was to generate a one‐dimensional diffraction grating to be used as a soft x‐ray monochromator. The structural analysis shows that the as‐grown film is almost a single crystal, where a new phase is present, characteristic of the layering process. The results indicate that it is now becoming feasible to produce new synthetic crystals by vapor deposition of two chemically quite dissimilar metals.

ISSN:0021-8979    

DOI:10.1063/1.331143

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The physical properties of Sb‐doped SnO2thick films, prepared by a repeating chemical spray deposition method, have been investigated. The films 1000–14 000‐A˚ thick were deposited on fused quartz, borosilicate glass, and soda lime glass substrates at 600 °C using an aqueous solution of a mixture of SnCl4and SbCl3. The films prepared by the method are homogeneous, and the electrical resistivity of the films on fused quartz and borosilicate glass substrates were found to be independent of the film thickness, and are 9.5×10−4&OHgr; cm, and 8.6×10−4&OHgr; cm, respectively. The resistivity of the films thicker than 4000 A˚ on soda lime glass substrates is almost constant, and is 1.8×10−3&OHgr; cm, although a large increase in the resistivity of the thinner films was observed. The optical band gap of the films on fused quartz and borosilicate glass substrates is also independent of the film thickness, and is almost the same: 3.75 eV. But the band gap of the films on soda lime glass substrates depends on the film thickness, and increases from 2.85 to 3.08 eV with increasing thickness from 2250 to 13 000 A˚. The Hall mobility and carrier concentration of the films were also measured. The results of x‐ray diffraction analysis and observations by SEM are described.

ISSN:0021-8979    

DOI:10.1063/1.331144

出版商:AIP    

年代:1982

数据来源: AIP