摘要:

Neutron energy dependence of the initial dislocation pinning rate was studied from 1.9 to 23.4 MeV on a copper sample. By comparing initial pinning rates from 0.5‐ and 1.0‐MeV electron irradiations and the neutron irradiations, and using the defect production rate for electron bombardments, an estimate of the free interstitial production cross sections (FIPCS) for neutrons was made. These FIPCS values are compared with several theories which predict the total number of Frenkel pairs produced as a function of recoil energy. Comparison with the simplest of these models (Norgett‐Robinson‐Torrens) showed good agreement with the trend of the energy dependence of the FIPCS. Additional comparison showed that only 1% or less of the predicted number of interstitials survive as free interstitials. A gold sample was also studied and results of 2‐MeV electron and 14.3‐MeV neutron irradiations are also presented.

ISSN:0021-8979    

DOI:10.1063/1.328153

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Atomic depth distributions for the low atomic number ions73Li,94Be, and115B implanted into channeled and random equivalent orientations in crystalline silicon have been studied. The atomic depth distributions were obtained by secondary ion mass spectrometry measurements on samples implanted to fluences low enough to preserve the integrity of the channeling components. All implants were performed at 150 keV into the ⟨100⟩ and ⟨110⟩ directions and into the (111) random equivalent orientation of float‐zoned (low‐oxygen) silicon crystals. The results show that in the three orientations studied the ion ranges decrease with increasing atomic numberZ1. This is indicative of the strong increase in electronic stoppingSefor theZ1=3, 4, 5 sequence. The increase in ion penetration in the channeling orientation is greater with decreasingZ1in the lower electronic stopping ⟨110⟩ channel than in the higher electronic stopping ⟨100⟩. Values ofSedetermined for channeled Li and Be at an ion velocity of 1.5×108cm/s are in agreement with published calculations and theSefor B is consistent with experimental measurements.

ISSN:0021-8979    

DOI:10.1063/1.328154

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Commercial manganin gauges were calibrated in a series of plane shock wave experiments. The calibration curve obtained is linear in the 0–1.5‐GPa range and curves for higher stresses (1.5–18.1 GPa). The linear portion is attributed to the elastic behavior of the gauge. This was confirmed by experiments which included rarefactions from free surfaces. The onset of hysteresis was found to be at 1.5 GPa. The experiments demonstrated that the gauge’s response does not depend on the target material in which the gauge is embedded. Also the thickness of the insulating layer which surrounds the gauge does not have any influence on its relative resistance changes.

ISSN:0021-8979    

DOI:10.1063/1.328155

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A specially designed 76‐mm cannon was used to drive small metal plates (copper, 3.175 mm thick) against metal target plates (steel, 6.250 mm thick) in order to study the fundamental parameters involved in the high‐velocity impact‐welding process. This method of study allowed experimental examination of the influence of each variable separately, in the classical mode. The results of these experiments were analyzed to define the required impact conditions for welding. A line of optimum weldability was identified and shown to be characterized by invariance in the metallic jet velocity. The analysis was also used to identity conditions applying to the transition zone between laminar and wavy interfaced welds.

ISSN:0021-8979    

DOI:10.1063/1.328156

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The known similarity between the wavy weld interface observed in high‐velocity impact welding of metals and the wakes behind an obstacle in a uniform stream was analyzed. The wavelength, the wave size, and the wave shape were established in terms of semi‐empirical relationships. The energy consumed in the formation of the interface wave was found to be over 90% of the collision energy for copper to steel welds. The Mathieu function was found to provide a very good approximation to the wave shape. The analysis was based on applying Birkhoff’s model of the swinging Foppl wake behind an obstacle as an analogy to determine the shape and size of the developed waves.

ISSN:0021-8979    

DOI:10.1063/1.328157

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The phonon spectra of Ga1−xInxAs have been studied by measuring the infrared reflectivity at near‐normal incidence in the 180 ∼400‐cm−1frequency range. Only one reststrahlen band corresponding to the GaAs‐like mode was observed forx≲0.2, and two bands were observed for the remaining composition. The data were analyzed by using the Kramers‐Kronig relationship and the dependence of the mode frequencies on alloy composition was interpreted on the basis of the modified cluster model including the effect of clusters. The fact that the calculated oscillator strength for the InAs‐like mode is substantially zero in the composition rangex≲0.2 explains the reason why phonons of the InAs‐like mode are not detected experimentally forx≲0.2. The clustering parameter representing the effect of clusters is determined by fitting the measured mode frequencies to the calculated compositional dependence and takes the maximum value near the midrange of alloy composition.

ISSN:0021-8979    

DOI:10.1063/1.328158

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Phase formation in the AuCu‐Al thin‐film system has been studied by nuclear backscatering of energetic ions and by x‐ray diffraction techniques. At temperatures between 150° and 220 °C Au2Al or Al2Cu are formed initially from Au‐rich or Cu‐rich solid solutiions, respectively. The growth kinetics are slower than in the corresponding bilayers of Al‐Cu or Al‐Au while the sequence of compound formation is unchanged.

ISSN:0021-8979    

DOI:10.1063/1.328159

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Parallel silicide contacts consisting of PtSi and NiSi with fixed ratios of contact areas were prepared for current‐voltage and capacitance‐voltage measurements of Schottky barrier height. These measurements were analyzed with models assuming a linear combination of thermionic emission currents or junction capacitances. The measured and the computed values of barrier height have been found to agree very well. A systematic diagnosis of parallel contacts under a variety of conditions is presented in the Appendix.

ISSN:0021-8979    

DOI:10.1063/1.328160

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Two dominant selenium‐related defects in silicon have been studied by transient capacitance and current techniques. For one of the centers, the A center, Arrhenius plots of thermal emission rates for electrons and holes (loget−1/T) give ’’thermal activation energies’’ ofEC−ET=0.52 eV andET−EV=0.62 eV, respectively. Although the electron‐capture cross section of the center is too large to be measured with our equipment, a conservative estimate gives a value larger than 10−14cm2. The electron‐capture cross section &sgr;tnBof the other center, the B center, showed aT−3.2temperature dependence and has a value of 3×10−15cm2at 100 K. From the measured data for &sgr;tnBandetnBa value of 0.30 eV for the Gibbs free energy of the B center is obtained. This energy value is constant and equal to the enthalpy in the temperature range investigated. Plotting logT2&sgr;tnBversus 1/T, an activation energy of 14 meV is obtained. This is interpreted as the energy separation between the lowest state accessible in a cascade capture process and the conduction band. In all samples, the concentrations of the A and B centers are found to be equal.

ISSN:0021-8979    

DOI:10.1063/1.328161

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electrical properties of the oxide films thermally grown from polycrystalline silicon have been examined. Without the electrode shape effects the films can sustain high electric fields (6.5 MV/cm) and do not trap a significant number of electrons at those fields. The high oxide leakage current found in the bumpy injection electrodes is correlated to the shape of the bump. The electric field distribution between two parallel bell‐shaped electrodes was computed numerically. Solutions suggest that the field enhancement cause by the geometrical shape of the injection electrode is the major cause for the observed high oxide current in the polycrystalline silicon‐(poly‐oxide)‐polycrystalline silicon structure.

ISSN:0021-8979    

DOI:10.1063/1.328162

出版商:AIP    

年代:1980

数据来源: AIP