摘要:

A temporally and spatially periodic light intensity distribution generates thermally in an absorbing sample a corresponding density variation which can be considered a standing sound wave. This thermal excitation of ultrasonic waves by modulated laser light has been investigated theoretically and experimentally. The sound waves were excited by two light beams of equal intensity derived from a mode‐locked ruby laser. The amplitude, velocity, and damping of the sound waves were examined by Debye Sears diffraction of argon laser pulses.

ISSN:0021-8979    

DOI:10.1063/1.1662780

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Prismatic dislocation loopsb= 1/2⟨101⟩, were observed around impurity precipitates in as‐grown magnesium oxide single crystals with a high percentage of Ca and Al impurities. The loops lay on {101} slip planes. By using the results of the dynamical theory of electron diffraction including absorption and stereo microscopy, the majority of the loops were identified asb= 1/2⟨101⟩ vacancy type. The possible chemical form of these impurities is discussed in view of the nature of the dislocation loops.

ISSN:0021-8979    

DOI:10.1063/1.1662781

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Misfit dislocations generated in (110), (112), and (113) siliconp‐on‐p+epitaxial wafers are investigated through x‐ray topography. Dislocations observed are of mixed type and arranged along the intersection of the four {111} planes with the specimen surface. The dislocations are formed by slip to relieve the interfacial shear resulting from the misfit.

ISSN:0021-8979    

DOI:10.1063/1.1662782

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Many theories have been proposed for the propagation of stress waves in metals. They are classified into three types by the constitutive equation; that is, the Ka´rma´n‐type theory, the Malvern‐type theory, and the Cristescu‐type theory. However, these proposed theories are not sufficient to explain certain facts which are found in the impact test of a thin rod consistently. For example, they fail to explain how the front of the stress wave always travels with the elastic‐wave velocity even in material prestressed into the plastic region, and the plateau of the uniform plastic strain remains in the neighborhood of the impact end. Therefore, in this paper, the authors apply the Johnston‐Gilman‐type constitutive equation to the theory of stress‐wave propagation and study the propagation of the stress wave produced in a thin rod by an impact of a long duration. The results of analysis account for the above‐mentioned two facts consistently, and, moreover, account for other phenomena which occur during the propagation of the stress wave not only in mild steel but also in other metals. From these results, the following conclusions are obtained. It is proper to use the Johnston‐Gilman‐type constitutive equation for the theory of the stress‐wave propagation in mild steel, and it seems that the forms of the constitutive equations of other metals may bear a close resemblance to that of the Johnston‐Gilman‐type constitutive equation. Though the Johnston‐Gilman‐type constitutive equation is based on the microscopic mechanisms of the dislocation theory, the theory of stress‐wave propagation in which it is used is essentially Malvern's theory, which has a noninstantaneous plastic response to an increase of the stress.

ISSN:0021-8979    

DOI:10.1063/1.1662783

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A theoretical analysis by Mitoff and Charles of electrode processes for an ionic material is criticized and corrected. These authors introduce three separate capacitances into their equivalent circuit where only one need appear. This frequency‐dependent diffusion‐discharge capacitance is calculated incorrectly by Mitoff and Charles, and earlier relevant work is ignored. Partial blocking small‐signal theory is used to show that Mitoff and Charles's experimental results on three different ionic materials can quite possibly by understood using such an approach, contrary to these authors' expectations.

ISSN:0021-8979    

DOI:10.1063/1.1662784

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Internal charge distribution in carnauba wax thermoelectrets was measured. It was found that substantial volume charges exist within the electrets. These charges form a characteristic permanent volume charge distribution which is essentially the same for all investigated (over 100) electrets regardless of the magnitude of the electric field used for polarizing the electrets, duration of polarization, electret age, surface charge, or storage conditions. The existence of this characteristic volume charge distribution indicates that the primary mechanism responsible for the electret effect in the carnauba wax thermoelectrets is a trapping of electric charges within the electret material rather than a permanent microscopic polarization of the material.

ISSN:0021-8979    

DOI:10.1063/1.1662785

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Alloying kinetics data on thin‐film materials systems of interest in large‐scale integration (LSI) technology are useful in the design of high‐temperature processing schemes. In the present work, we have investigated the kinetics and mechanism of WSi2formation in the thin‐film system W/PtSi/Si, which is encountered in the Ohmic contact and Schottky barrier areas of silicon integrated circuits.In situx‐ray diffractometer measurements were carried out on various thin‐film samples in the temperature range 690–840 °C. All the samples consisted of 2000‐Å W film on 900‐Å PtSi on 10‐mils‐thickn‐type (100) Si doped with arsenic to a resistivity of 10 &OHgr; cm. The amount of WSi2formed was found to be equal to the amount of W consumed, indicating that an excess of Si atoms (diffusing species) is present at the reaction interface. The rate of transformation of W to WSi2first increases with time and then it decreases. The data can be represented in terms of the generalized kinetic law:x= 1‐exp[−K(T)tn], wherexis the volume fraction of W transformed,K(T) is a temperature‐dependent rate constant,tis time, and the indexnis experimentally found to be equal to [inverted lazy s]1.35 in most cases of W/PtSi/Si samples annealed between 690 and 840 °C. A relatively high thermal activation energy of [inverted lazy s]4.4 eV/mole was deduced from an Arrhenius plot of half‐time for transformation vs reciprocal of the annealing temperature. A comparison of the present results with those available on a W&sngbnd;Si thin‐film system indicates that an intermediate layer of PtSi substantially accelerates the rate of formation of WSi2and that PtSi may be also affecting the thermodynamic processes involved in WSi2formation. It is suggested that the WSi2nucleation process may involve, simultaneously, creation of W&sngbnd;Si bonds at the expense of Pt&sngbnd;Si bonds and restoration of the latter by out‐diffusing silicon atoms. All the WSi2nucleation sites at the W/PtSi interface are probably saturated before appreciable growth occurs.

ISSN:0021-8979    

DOI:10.1063/1.1662786

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The thermal expansion coefficients of the corundum structure oxides Ti2O3and V2O3were measured by elevated‐temperature x‐ray diffraction techniques, the former to 300 °C and the latter to 1000 °C. Compared with corundum, both of these oxides exhibit deviations in their thermal expansion behavior which may be attributed to electronic interactions of the transition metal cations.

ISSN:0021-8979    

DOI:10.1063/1.1662787

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

TheK&bgr;5emission andKabsorption spectra of Mn in MnP are obtained with a two‐crystal spectrometer and a 50‐cm bent‐crystal spectrograph, respectively. TheK&bgr;5spectrum consists of a main band and a subband. The high‐energy edge of theK&bgr;5band coincides with theKabsorption edge. This suggests that MnP is a metallike compound. The obtained spectra of MnP are compared with theKspectra of metallic manganese, the PKabsorption spectrum of MnP, and the energy‐band structure of MnP. The main band and the subband in theK&bgr;5emission spectrum correspond to the filled 3dbands of manganese and the 3pband of phosphorus, respectively. The first and the second maxima in theKabsorption spectrum correspond to the empty 3dbands (related to theegorbitals containing somesandpcharacter) and 4pband of Mn, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1662788

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The electrical and mechanical features of a thermally induced interaction between platinum silicide and aluminum have been investigated. It has been found that a diffusion‐controlled reaction occurs between these two materials which results in conversion of platinum silicide to the intermetallic PtAl2. The activation energy for this process is found to be 0.77 eV. As platinum silicide Schottky diodes with aluminum contacts are sintered for increasing time periods, this reaction propagates to the platinum silicide‐silicon interface and the effective barrier height of the metal‐semiconductor junction is observed to drop sharply to a value below that of aluminum‐silicon Schottky diodes. As longer sinter cycles are performed the effective barrier height rises to a value characteristic of aluminum‐silicon contacts. This effect is shown to be a result of diffusion of aluminum through the reacted material and the formation of an essentially aluminum‐silicon contact at the silicon substrate. The mechanical features of the platinum silicide‐aluminum reaction observed on test devices are correlated with the electrical effects of this reaction noted on Schottky diodes.

ISSN:0021-8979    

DOI:10.1063/1.1662789

出版商:AIP    

年代:1973

数据来源: AIP