摘要:

An optimal shape for internal friction measurements using a dual cantilevered beam is described. The new shape is analyzed by a finite element method, in order (a) to optimize its parameters to reduce parasitic interactions with the sample holder, and (b) to calculate the stress distribution in the vibrating sample. The numerical analysis shows that the interactions between the sample and its holder are much weaker for the new shape than for the classical flexural vibration of a simple cantilevered beam. The predictions of the numerical analysis are compared to experimental results on a niobium sample at low temperature.

ISSN:0021-8979    

DOI:10.1063/1.336081

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Many chemical reactions can only take place after a diffusion process involving one of the reagents. This work examines how a reagentAdiffuses into a cylindrical fiber containing a uniform distribution of impuritiesB, when an irreversible second‐order reactionA+B→ABcan take place. The reaction is considered to be the rate‐controlling process. The determination of the different concentration profiles requires the solution of a system of nonlinear partial differential equations for which an approximate solution is derived. It is shown how the diffusion profile of the reagent is modified by the reaction and how the formation of the reaction product depends on the diffusion process. This interdependence is illustrated by some specific examples. For small values of time the concentrations of the diffusing substanceAlie below the values one would expect if no reaction took place. This difference depends on the reaction constantkand the number of impurities. The analysis of the differences between in‐ and out‐diffusion experiments is one way of measuring the influence of the reaction on the diffusion process. One possible application of the present model is the description of hydrogen diffusion and hydroxyl formation in optical fibers.

ISSN:0021-8979    

DOI:10.1063/1.336082

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A detailed study of transient thermal processing of S‐doped epitaxial GaAs wafers, both with and without ion‐implantation damage being present, has been performed. The average diffusivity of S is given for the temperature range 950–1050 °C, and is shown to be dependent on the position of any lattice damage present, the surface condition (capped or capless), and the annealing regime employed (thermal or rapid thermal). The mobility of the S‐doped region is degraded by rapid annealing, and the extent of this degradation is a function of the experimental conditions employed. Implantation of Si (which occupies a Ga site) into S‐dopedn+regions (S occupies an As site) failed to increase the electrical activity of the region above the often observed limit of 2×1018cm−3.

ISSN:0021-8979    

DOI:10.1063/1.336083

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A systematic study of arsenic redistribution in Ni, Cr, Ta silicide forming systems has been performed by implanting arsenic into metal layers or into single‐crystal silicon substrates. During silicide formation arsenic accumulates near the interface region, incorporates in the silicide, or diffuses out of the silicide into the surrounding ambient. Differences in the dopant redistribution are related to the arsenic initial location relative to the moving species in silicide formation and the diffusivity of dopant atoms at the metal‐silicon reaction temperature.

ISSN:0021-8979    

DOI:10.1063/1.336084

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Both epitaxial tetragonal and hexagonal WSi2(t‐WSi2andh‐WSi2) were grown locally on (111)Si. The best epitaxy was obtained in 600–1100 °C two‐step annealed samples. The orientation relationships betweent‐WSi2and Si are [110]WSi2∥[111]Si and (004)WSi2∥(2¯02), whereas those betweenh‐WSi2and Si are [0001]WSi2∥[111]Si and (202¯0)WSi2∥(202¯)Si. Interfacial dislocations, 80 A˚ in spacing, were identified to be of edge type with (1/6)⟨112⟩ Burgers vectors. Two step annealings were found to be effective in improving the epitaxy and relieving the island formation of WSi2on Si. Significant intermixing of W and Si atoms during the preannealing is proposed to account for the effects.

ISSN:0021-8979    

DOI:10.1063/1.336308

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The reactions of Pd on atomically clean or air‐exposed (100) and (110) GaAs surfaces at temperatures between 20 to 500 °C in different ambients were investigated by transmission electron microscopy. Interfacial reactions quite different from previous x‐ray results were observed and two new Pd‐Ga‐As ternary phases were identified for the first time. At lower temperatures (T≲250 °C) the formation of a ternary phase PdGa∼0.3As∼0.2, which has a hexagonal structure very similar to that of Pd2Ge or Pd2Si witha0=b0=0.672 nm andc0=0.340 nm, was observed. This ternary phase is epitaxially oriented with (12¯0)ternary∥(100)GaAsand [001]ternary∥[011]GaAson (100) GaAs substrates, and with (11¯0)ternary∥(110)GaAsand [001]ternary∥[11¯0]GaAson (110) GaAs substrates. At temperatures between 350 and 500 °C only one phase, PdGa, was observed to form in a high vacuum environment, whereas in a forming gas ambient, either a mixture of PdAs2and another ternary phase PdGa∼0.6As∼0.4(at 350 °C) or a mixture of PdAs2and PdGa (at 500 °C) was observed. The ternary phase PdGa∼0.6As∼0.4is also hexagonal in structure witha0=b0=0.947 nm andc0=0.374 nm. The PdGa phase formed at high temperature is epitaxially oriented on (100) substrates with (110)PdGa∥(100)GaAsand [1¯11]PdGa∥[011]GaAs, but is randomly oriented on (110) substrates. All these observations indicate that the Pd‐GaAs reactions atT≳350 °C are very sensitive to the ambient conditions but not as sensitive to the GaAs surface cleanliness or substrate orientation. Correlation of these structural observations to ultraviolet and x‐ray photoelectron spectroscopy data obtained from the same reacted interfaces are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.336085

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Inert markers (evaporated tungsten and silver) were used in growth studies of silicides formed both by thermal annealing and by ion mixing in the Ni/Si, Pd/Si, and Cr/Si systems. The markers were initially imbedded inside silicides and backscattering spectrometry was used to determine the marker displacement after different processing conditions. The results obtained in thermal annealing are quite consistent with that found in previous investigations. Ni is the dominant diffusing species in Ni2Si, while Si is the diffusing species in CrSi2. In Pd2Si, both Pd and Si are moving species with Pd the faster of the two. In contrast, in growth of silicides by ion irradiation Si is the faster diffusing species in all three systems.

ISSN:0021-8979    

DOI:10.1063/1.336086

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In1−xGaxP epitaxial layers were grown on (100) GaAs substrates by liquid‐phase epitaxy using supercooling technique. The lattice mismatch normal to the wafer surface between In1−xGaxP layer and GaAs substrate varies linearly with the supercooled temperature of the growth solution. The composition‐pulling phenomenon was not observed in this study. The growth rate, the intensity, and the full width at half maximum of the photoluminescent spectrum are also dependent on the supercooling temperature. It is shown that the narrowest full widths at half maximum of photoluminescent peak are 10.6 and 35 meV at 14 and 300 K, respectively, when &Dgr;Tis 6 °C, and the strongest intensity is occurred at &Dgr;T=12–18 °C. Carrier concentrations of undoped epitaxial layers are in the range of 1016cm−3measured by capacitance‐voltage method at 300 K and Hall method at 77 and 300 K. The optimum growth condition was then determined.

ISSN:0021-8979    

DOI:10.1063/1.336087

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect have been studied in &ggr;‐phase La3−xS4(LaSy) in the composition range 0.04≤x≤0.3 (1.35≤y≤1.48) in order to ascertain its suitability for high‐temperature (300 to 1400 K) thermoelectric energy conversion. In this temperature and composition range the material behaves as an extrinsic semiconductor whose degenerate carrier concentration is controlled by the stoichiometric ratio of La to S. A maximum figure‐of‐merit (Z) of ∼5×10−4K−1at a compositionx=0.3,y=1.48 (LaS1.48) was obtained.

ISSN:0021-8979    

DOI:10.1063/1.336088

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

ZnSe films have been grown on ⟨100⟩, ⟨110⟩, and ⟨111⟩BGaAs surfaces, using the metalorganic chemical vapor deposition technique. The electrical transport properties and lattice structure characteristics of these films have been studied using a van der Pauw technique and high‐resolution transmission electron microscopy. The electrical and structural properties of these films vary significantly with growth direction. In (100) layers, the observed defects are similar in nature to isolated compensated centers. For other orientations, observed properties are best described in terms of extended defects and grain boundaries.

ISSN:0021-8979    

DOI:10.1063/1.336089

出版商:AIP    

年代:1985

数据来源: AIP