摘要:

Anomalous carrier tail generation in BF+2ion‐implanted layers through gas‐ion interaction is quantitatively examined by a combination of gas pressure measurements and carrier profile measurements. The collision cross sections of He, Ar, Kr, and N2gases with BF+2ions are derived from the relative peak carrier concentrations of the tail and residual gas pressure relationships. Below 10−2Pa, simple gas‐ion interaction occurs and the collision cross section is around 10−14cm−2. A gas pressure of less than 10−5Pa in the implanter ion path is necessary to almost completely eliminate the anomalous tail generation. On the other hand, more than 4×10−1Pa, multiple collisions between the ions and the residual gas atoms/moleculs occur and the tail carrier concentration become saturated. BF3gas molecules are also foud to generate B+ions through collisions with BF+2ions.

ISSN:0021-8979    

DOI:10.1063/1.325763

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Detailed x‐ray diffraction investigations, based on precise measurements of the position, asymmetry, broadening, and shape of x‐ray diffraction profiles 111, 200, 220, 311, 222, and 400 recorded in a counter diffractometer, have been performed on vacuum‐evaporated fcc lead films in the range of thickness ∼300–6500 A˚. The films are deposited on glass substrates at a residual air pressure ∼5×10−5Torr for both normal and oblique vapor directions. The complete analyses have revealed clearly the microstructural features in these vapor‐deposited films. Near‐isotropy in the domain size and rms strain values with a relatively less size effect has been observed. The magnitudes of the respective compound fault parameters, close to the error limits, indicate the total absence of intrinsic (&agr;′), extrinsic (&agr;″), and even growth twin (&bgr;) stacking faults in the films. The dislocation density (&rgr;) is typical for thin films and is ∼1011cm/cm3. The residual internal stresses (&sgr;), compressive in nature, are small, and the small lattice parameter changes show a contraction in the plane of the film. The films are found to be highly oriented along [111] irrespective of the source position. It has been observed that the microstructural parameters exhibit more or less a regular variation with film thickness and are less influenced by the source position.

ISSN:0021-8979    

DOI:10.1063/1.325764

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The ferrobielastic behavior of &agr;‐quartz crystals under compressive stress has been investigated making use of the piezoelectric and piezo‐optic effects. The direction of mechanical stress was so chosen that secondary twinning is favored. Above a threshold of approximately 0.5 GPa, ferrobielastic switching results in a complete orientation reversal. Unexpectedly the mere removal of the mechanical constraint leads to a complete restoration of the original orientation. This retrotransition occurs between 0.1 and 0.025 GPa. This effect is discussed in terms of a simple thermodynamical model.

ISSN:0021-8979    

DOI:10.1063/1.325765

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Using one‐dimensional strain conditions, the dynamic stress‐wave response of polycrystalline Al2O3was measured with interferometry in both stress‐wave loading and unloading to about 16 GPa and with slanted resistor gauges in loading to about 50 GPa. The stress‐wave loading and unloading measurements were of high resolution and showed a 9.1‐GPa elastic precursor wave (velocity 10.9 km/s) followed by a slower dispersive permanent deformation wave. Unloading was elastic in the stress range of these experiments. Both loading and unloading wave propagation were modeled well with a Maxwellian elastic‐stress‐relaxing model with a yield stress of 5.8 GPa and a relaxation time of 70 ns. The rate‐dependent model correctly predicts both the dispersion of the permanent deformation wave and the unloading‐wave behavior. The bulk pressure‐volume behavior of alumina is given by the shock‐velocity–particle‐velocity relationship ofUs=8.14 +1.28up(km/s). Thermodynamic corrections to the dynamic bulk response yielded isothermal pressure‐volume results which agreed well with direct hydrostatic determinations on polycrystalline Al2O3and with results deduced from ultrasonic determinations on Lucalox. Permanent deformation of Al2O3from a micromechanical standpoint appeared to be compatible with a model involving general microcracking throughout the volume of the material. This model is supported by the lack of an appreciable spall strength. When the yield process is ascribed to the onset of microfracture, which depends upon the initial flaw size and distribution, the earlier results on single crystals are phenomenologically related to the stress‐wave behavior observed during this study on polycrystalline alumina.

ISSN:0021-8979    

DOI:10.1063/1.325766

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

To date, zinc oxide varistors have been subjected to uniaxial compression to 5 kbars and hydrostatic pressures to 10 kbars. These results show a behavior between current and pressure empirically described byIL∼P7. This paper presents results of experiments in which zinc oxide varistors were subjected to hydrostatic compression up to 25 kbars. Results show a significant departure from previously reported results. The leakage current remains constant at first until a pressure of 6–7 kbars is attained. It then rises sharply and nonlinearly to a maximum value of about 55 &mgr;A at a pressure of 15 kbars, and subsequently the leakage current decreases by about two orders of magnitude as the pressure increases from 15 to 25 kbars. The limit of 25 kbars is determined by the pressure cell design and materials used. The results presented here also suggest that the varistor behavior with pressure depends on thermal annealing and strain‐induced damage processes.

ISSN:0021-8979    

DOI:10.1063/1.325767

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Bounds on the effective elastic moduli of randomly oriented aggregates of orthorhombic crystals have been derived using the variational principles of Hashin and Shtrikman. The bounds are considerably narrower than the widely used Voigt bound and Reuss bound. In many instances, the separation between the new bounds is comparable to, or less than, the uncertainty introduced by experimental errors in the single‐crystal elastic stiffnesses. The Voigt‐Reuss‐Hill average lies within the Hashin‐Shtrikman bounds. several percent.

ISSN:0021-8979    

DOI:10.1063/1.325768

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A degenerate parametric oscillator which is driven by a random current additionally applied to a sinusoidal pumping current is found to exhibit a new type of oscillatory‐to‐nonoscillatory transition. This noise‐induced phase transition has a different kind of critical behavior from that observed in usual phase transitions, that is, near the threshold the variance of the fluctuating output current remains constant, however, the critical slowing‐down does occur. A stochastic equation for the parametric oscillation which includes a random force multiplied by the amplitude itself is derived and the experimental results are fully accounted for in terms of that equation.

ISSN:0021-8979    

DOI:10.1063/1.325769

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Variations of the XPS spectra of Fe1−xO crystal and iron metal oxidized in air were studied when the samples were heated in a vacuum. The structural variations observed by XPS can be explained by the phase diagram of the iron‐oxygen system. The intensity ratio of O 1sto Fe 2p3/2for Fe1−xO at 800 °C in thermal equilibrium was smaller than that of the sample quenched from 800 °C to room temperature. This indicates that quenching the sample changes the surface structure. FWHM (full width at half‐maximum) of 2.2 eV of O 1sfor Fe1−xO was larger than that of 1.7 eV for &agr;‐Fe2O3. The broader FWHM is due to the large value ofxand clustering of the cation vacancies in Fe1−xO. The binding energies and spectral profiles of Fe 3sand Fe 2p1/2,3/2for Fe1−xO coincided with the spectra for Fe2SiO4or FeTiO3having only divalent iron ions.

ISSN:0021-8979    

DOI:10.1063/1.325770

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The amplitude‐frequency effect in quartz crystal resonators is a consequence of the nonlinear elastic behavior of the crystal. However, dissipation due to internal losses can also induce frequency changes caused by amplitude variations, but in this case with a large time constant. Nonuniform heating introduces thermal stresses and density changes which act on a propagating wave by nonlinear coupling through the third‐order elastic constants. Both the heat and wave equations are solved for the quartz crystal, and thermal exchanges with the surrounding medium are considered for several types of mounting. The resonator frequency change due to variation of the driving level, which appears as the indirect amplitude‐frequency effect, is calculated. It is shown that the large time constants experimentally observed can be mainly attributed to thermal diffusion through the connection wires.

ISSN:0021-8979    

DOI:10.1063/1.325771

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Contact reactions in the temperature range 250–650 °C between (100) Si and Pd‐W binary alloy films of composition Pd80W20and Pd30W70have been studied by a combination of ion backscattering, x‐ray diffraction, and current‐voltage measurement of Schottky barrier height. For the Pd‐rich alloy, the reaction around 400 °C produced the silicide Pd2Si by depleting Pd from the alloy and resulted in the formation of a two‐layer structure, W/Pd2Si/Si. We have found that the W layer has served effectively as a diffusion barrier for the subsequently deposited Al, indicating that a rectifying contact and its diffusion barrier can be fabricated simultaneously. At higher reaction temperatures, the W layer transforms to WSi2with some mixture of Pd2Si. The alloying of Pd with W has been found to increase the formation temperature of Pd2Si but decrease that of WSi2. In the Pd80W20reaction, Pd2Si forms around 400 °C and WSi2around 500 °C. In the Pd30W70reaction, Pd2Si forms around 500 °C and WSi2around 650 °C.

ISSN:0021-8979    

DOI:10.1063/1.325772

出版商:AIP    

年代:1979

数据来源: AIP