摘要:

The first Brillouin‐scattering measurements of single‐crystal Mg2SiO4have been made at 1 atm and pressures up to 40 kbar in a diamond‐anvil cell at room temperature. The elastic moduli C11,C22,C33,C44,C55, and C66, and their pressure derivatives were obtained. These results were compared with those obtained by ultrasonic measurements up to 10 kbar. The observation of lowdCij/dPslopes for the transverse moduli. C44, C55, and C66, and the evidence for negative second derivatives as well, support Poirier’s proposed mechanism for the olivine→spinel transition due to gliding of close‐packed oxygen layers. Moreover, the numerical relationships among photoelastic constants were determined by studying the intensity ratio of LA to TA modes.

ISSN:0021-8979    

DOI:10.1063/1.329968

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The results of photoluminescence measurements ofp‐type AlxGa1−xAs:Ge (with 0.03<x<0.39) grown by liquid phase epitaxy are presented. An investigation of the composition and temperature dependencies of the acceptor‐related peak in this range shows that Ge behaves as a shallow effective mass‐like center. The discontinuity in the variation in peak energy versus composition that occurs atx= 0.30 is explained rather in terms of a crossing of donor levels associated with the direct and indirect band gaps. It is also shown that the luminescence is characteristic of donor‐acceptor recombination involving shallow donors forx<0.30, whereas a deep donor or a vacancy complex is indicated forx≳0.30. The broad emission band at ∼1.5 eV has also been investigated but its source has not been identified. The presence of this band in the room temperature spectrum and the implications for characterization of light‐emitting devices are discussed.

ISSN:0021-8979    

DOI:10.1063/1.329969

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Photoluminescence and infrared absorption in liquid encapsulated Czochralski‐grown InP single crystals are discussed. Photoluminescence intensities, intensity ratio, and half‐width due to donor‐valence band and conduction band‐acceptor transitions are clarified at 77 K as functions of carrier concentration. Acceptor binding energies of Zn, Cd, and Hg impurities are determined. Correlations between free‐carrier absorption coefficient and carrier concentration to mobility ratio are also examined. It is concluded that carrier concentration, compensation ratio, and mobility in InP single crystals can be determined nondestructively by combining their photoluminescence and infrared absorption spectroscopies.

ISSN:0021-8979    

DOI:10.1063/1.329970

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A model is proposed for the observed hysteretic behavior of ac‐coupled ZnS:Mn thin‐film electroluminescent devices. The following mechanisms are invoked: (1) tunnel injection from ZnS‐dielectric interfaces (E4106V/cm), (2) electron‐hole pair generation, (3) deep trapping of holes, leading to space‐charge formation, (4) charge storage at the ZnS‐dielectric interfaces, and (5) direct recombination of injected electrons and trapped holes. When these mechanisms are combined in a self‐consistent numerical simulation model, a bistability of charge transfer versus applied voltage is obtained which exhibits many of the characteristics of the observed device behavior. Experimental evidence in support of the individual assumptions is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.329971

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The Maxwell‐Garnett theory is generally used to describe the optical behavior of aggregated metallic films. This theory is, however, restricted to ultrafine particles whose main dimension can be considered very small compared to that of the wavelength. With particle dimensions in experiments generally larger than 10 nm, this approach is no longer valid for many metals. The purpose of the present work is, therefore, to revise the dipole approximation to include frequency‐dependent terms. The theory is also extended to quadrupolar terms, in order to assess the relative importance of these latter when the aggregates are no longer very small compared to the wavelength. Applications to real metals are discussed.

ISSN:0021-8979    

DOI:10.1063/1.329972

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Refractive indices and absorption coefficients of In1−xGaxP1−yAsyfory= 0 to 1 lattice matched to InP and of GaAs and GaP have been measured by ellipsometry in the wavelength range between 365 and 1100 nm. The high‐purity layers (7×1014<n<2×1016cm−3) used here were grown by liquid phase epitaxy. The quaternary refractive indices were also calculated from the measured indices of the constituent binary compounds by averaging the quantity (&egr;−1)/(&egr;+2). The &egr; values were all taken at the same energy separation from the respective band gaps. The results of this new averaging procedure are compared with the measured indices and with the refractive index steps to InP deduced from lasers. In addition, the absorption coefficient of InP near the band gap was measured as a function of the doping level. Finally, the temporal growth of the natural oxide layer thicknessdoxon various InP and GaAs samples was determined by ellipsometry. For InP, the increase ofdoxis 0.39 nm per decade of time.

ISSN:0021-8979    

DOI:10.1063/1.329973

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The CO2laser annealing characteristics of high‐dose boron‐ and arsenic‐implanted silicon were studied by isothermal annealing experiments. A different annealing behavior at different annealing temperatures was found. At high annealing temperatures, a complete electrical activation was achieved, but after a prolonged annealing time, a relaxation of metastable concentrations takes place. At low doses, this phenomenon does not occur. The electrical activation energy is 5.8 eV for boron‐implanted silicon (1.3×1016cm−2, 120 keV), for annealing temperatures between 1045 and 1140 ° C.

ISSN:0021-8979    

DOI:10.1063/1.329974

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

An apparatus consisting of an optical microscope with a hot stage attachment capable of simultaneously nonuniformly heating and mechanically loading small single crystals of salt was used to measure the velocities of all‐liquid inclusions NaC1 and KC1 specimens under various conditions of temperature, temperature gradient, and uniaxial stress. The rate‐controlling elementary step in the migration of the inclusions was found to be associated with interfacial processes, probably dissolution of the hot face. Dislocations are required for this step to take place. The small number of dislocation intersections with small inclusions in nearly perfect crystals causes substantial variations in the velocity, a sensitivity of the velocity to mechanical loading of the crystal, and a velocity which varies approximately as the second power of the temperature gradient.

ISSN:0021-8979    

DOI:10.1063/1.329975

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A containerless low‐gravity environment, produced within a 32‐m drop tube has been used to undercool and solidify Nb(1−x)Gexalloys for 0.13⩽x⩽0.27 with sample diameters in the range of 2–4 mm. Even for modest undercoolings of 100 K, evidence is found for the formation of metastable Nb3Ge. For major undercoolings in the range of 300–500 K, the x‐ray diffraction studies on these samples revealed the A‐15 structure with lattice constants consistent with the values obtained on chemical vapor deposited films. The instabilities of Nb3Ge at temperatures near the solidification temperature are revealed by quenching the samples in oil. TheTcwidths vary from broad, similar to splat‐solidified specimens, to narrow, similar to thin‐film values, depending upon the high temperature solid state quenching rates in oil. The importance of maintaining a stoichiometric composition near 25 at. % Ge and the requirements for longer processing times are also revealed in the experiment.

ISSN:0021-8979    

DOI:10.1063/1.329976

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The alloy Ti‐6Al‐4V has been implanted with carbon and nitrogen ions. The microstructure produced by these implants is found to contain fine particles of TiC and TiN, respectively. Rotating beam fatigue tests show improved fatigue life for both implants, with the superior carbon implantation giving a 20% increase in endurance limit and a factor of 4–5 lifetime increase at higher stresses over unimplanted material. A dose of 1×1017at./cm2is required to obtain the maximum effect. Fatigue cracks have been observed to originate up to 150 &mgr;m below the surface, indicating a complex interaction between the implanted layer and the fatigue failure process.

ISSN:0021-8979    

DOI:10.1063/1.329977

出版商:AIP    

年代:1982

数据来源: AIP