摘要:

The origin of the tail on the distribution of phosphorus atoms implanted into misaligned silicon crystals has been established by measuring the number of phosphorus atoms transmitted through thin silicon crystals during implantation. Experiments on ⟨110⟩ and ⟨100⟩ crystals show that the tail is due entirely to atoms which are scattered into channels. The preparation of crystals 0.4–0.8 &mgr;m thick from epitaxial layers by selective electrochemical etching and ion beam thinning is described and the measurement of their thickness by backscattering techniques is discussed. It is suggested that the tails on the profiles of other dopants in silicon are also due to atoms which have entered channels in the crystals.

ISSN:0021-8979    

DOI:10.1063/1.1663203

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Edge‐ and screw‐dislocation velocities in iron‐doped magnesium oxide single crystals containing dislocation dipoles and 90 ppm iron have been measured as a function of the stress (at stresses below the macroscopic yield stress), temperature, and valence state of the iron impurities to identify the rate‐controlling drag mechanisms for dislocation mobility. Edge dislocations have been observed to move faster than screw dislocations in the Fe2+and Fe3+valence states over the stress and temperature regimes investigated. The edge and screw dislocations move faster in reduced samples than in oxidized samples. From the analysis of the edge‐ and screw‐dislocation velocity data in terms of the activation parameters (volume, enthalpy, total enthalpy, and the stress exponent of dislocation velocity), it is proposed that the screw‐dislocation mobility in MgO single crystals containing dislocation dipoles and 90 ppm iron in the oxidized state is controlled by the interaction of dislocations with noncentrosymmetric defects(FeMg  ·−V″Mg). However, the edge‐dislocation mobility in the oxidized crystals is governed by the interaction of the edge dislocations with the dislocation dipoles. Moreover, the edge‐ and screw‐dislocation mobilities in the reduced state are also controlled by the interaction of the edge dislocations with the dislocation dipoles.

ISSN:0021-8979    

DOI:10.1063/1.1663204

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The frequency characteristics of the surface displacements of the Lamb waves excited by interdigital transducers on unpolarized piezoelectric ceramic plates have been analyzed by using the same method as Tseng's analysis of Rayleigh wave excitation. This analysis has lead to the conclusion that the transducer operates most effectively when the wavelength of the Lamb wave is equal to the half‐period of the electrode. The dispersive characteristics of the zeroth modes in a comparatively thick specimen are also shown. Our discussion dwells on the frequency dependence of the surface displacement on the total number of the electrode fingers in a transducer and the electrode configurations.

ISSN:0021-8979    

DOI:10.1063/1.1663205

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Platinum silicide formation has been studied by Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) in conjunction with argon ion depth profiling. These techniques were used to probe the chemistry of the interface between the Pt metal and PtSi formed from two standard platinum deposition processes: dc sputtering and filament evaporation. The results indicate that after sintering in nitrogen, the PtSi is separated from the platinum metal by a ``protective'' layer which has tentatively been identified as PtSiO4. This ``protective'' layer has a significantly slower etch rate in standard etchants than the platinum metal and platinum silicide and may be formed during sintering by an interaction between the platinum metal and the native silicon dioxide. The platinum silicate identification is based on the XPS ``chemical shifts'' found for both the platinum and silicon core levels. The silicate layer formation appears to be independent of the technique for platinum deposition.

ISSN:0021-8979    

DOI:10.1063/1.1663206

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We report results of extensive measurements on the acousto‐optic properties of several sulfosalt‐type chalcogenide crystals. These materials typically are transparent from the near ir to the intermediate ir, with refractive indices ranging from 2.5 to 3. Their acoustic velocities are among the lowest of any material, and ultrasonic attenuation remains low for frequencies to 500 MHz. These properties lead to exceptionally high acousto‐optic figures of merit.

ISSN:0021-8979    

DOI:10.1063/1.1663207

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Impurity segregations and their interactions with domains and dislocations in KNbO3single crystals have been studied. In the technique used, impurity structures in the bulk are first brought to the surface by removing layers of crystal without stress by methyl alcohol. The domain structure in the crystal remains completely undisturbed in this process. The dislocation pattern is then revealed by etch pits produced with an etchant such as a mixture of a concentrated solution of ammonium acetate in water and hydrogen peroxide (30% wt/vol) in the volume ratio 1 : 2. It has been found that impurity segregations interfere quite appreciably with domain formation. Segregations around arrays of edge dislocations form surprisingly straight lines parallel to pseudocubic ⟨100⟩ directions, appearing very similar to 60° domain lines under reflected light. Under these conditions, they prevent the formation of a 60° domain. Domain walls terminate at such lines, and may also be bent as a result of segregation‐dislocation interactions, occupying crystallographically irregular positions. These and other observations are discussed, providing the necessary microscopic and interferometric evidence.

ISSN:0021-8979    

DOI:10.1063/1.1663208

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Acoustic surface wave (ASW) components have been tested by visualizing the acoustic field amplitude and phase distribution in real time in the 15–25‐MHz frequency range. The properties of some useful devices are reported here.

ISSN:0021-8979    

DOI:10.1063/1.1663209

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper describes electro‐optically induced tunable deflection in the plane of a waveguide structure by utilizing the liquid‐crystal property of tunable birefringence together with appropriately designed electrodes. The magnitude of tunable deflection achieved in this experiment (>20°) had only been demonstrated in passive structures in the past. Furthermore, by changing the device parameters slightly, electrically controlled total internal reflection or refraction in the plane of the waveguide structure was demonstrated. This allowed operation of the device as a switch where the guided beam was deflected or ``switched'' through a very large angle (>70°) in the plane of the guide.

ISSN:0021-8979    

DOI:10.1063/1.1663210

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The adsorption and condensation of Cu up to several monolayers in thickness on tungsten {110} and {100} single‐crystal surfaces are studied by combining low‐energy electron diffraction, Auger electron spectroscopy, thermal desorption spectroscopy, work‐function measurements, and quartz microbalance thickness measurements in one experimental system. The results show drastic differences in the evolution of the structure, work function, and desorption behavior between {110} and {100} surfaces. These differences are understandable in terms of the atomic roughness of the surfaces.

ISSN:0021-8979    

DOI:10.1063/1.1663211

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In a simple model of a cubic lattice with piecewise linear and nearest‐neighbor interactions a solution is obtained for the motion of two parallel screw dislocations of the same sign, under the action of a constant applied stress. The only damping mechanism considered is the emission of sound waves. The important parameters are the external strainsand the dislocation separation &agr;. They are determined by energy balance and the boundary conditions imposed by the force law. The main result is the existence of multiple branches in the strain versus velocity curve, the lowest of which corresponds to an external strain less than that of a single dislocation. However, in the snapping bond model, two dislocations, as well as a single dislocation, cannot move at supersonic velocities without causing a breakdown of the crystal.

ISSN:0021-8979    

DOI:10.1063/1.1663212

出版商:AIP    

年代:1974

数据来源: AIP