摘要:

The formation of intermetallics in copper–tin bimetallic couples has been studied from room temperature to 183 °C by measuring the evolution of contact resistance and composite electrical resistance with time and temperature in order to assess the kinetic behavior of the system. X‐ray diffractogram (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies have also been performed on the samples. As regards bulk diffusion, copper diffuses interstitially into tin rapidly at room temperature with the formation of &eegr;’‐Cu6Sn5intermetallic compound. Further diffusion through this phase as evaluated by composite electrical resistivity measurements is given by 0.40 eV, assuming a model of defect‐assisted diffusion into the grains. The grain‐boundary diffusion is found to occur with an activation energy of 0.78 eV as estimated from contact resistivity measurements. SEM confirms the presence of grain‐boundary diffusion of tin in copper, whereas XRD and TEM measurements indicate the growth of &eegr;’intermetallics at room temperature which exists up to 90 °C when it transforms to the &egr;‐Cu3Sn phase. The presence of tin whiskers on the tin surface has also been occasionally observed.

ISSN:0021-8979    

DOI:10.1063/1.345324

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The growth of the Pd2Si thin fllms on Si(111) substrates has been monitored by aninsitux‐ray diffraction technique in vacuum and in helium atmosphere from 160 to 250 °C. A familiar parabolic growth rate was found, confirming the diffusion‐controlled film growth process. The activation energies were found to be 1.34 and 1.37 eV for the measurements performed in vacuum and helium environment, respectively. Stress relaxation in the growing Pd2Si fllm was observed when the reaction temperature exceeds 200 °C. The relaxed films showed a higher degree of texture as evidenced by the rocking curve measurements.

ISSN:0021-8979    

DOI:10.1063/1.345325

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A convenient kinetic uptake method has been employed to determine the absolute saturation monolayer coverage of C2H2and C2H4on a Si(100)(2×1) surface. Such measurements are important for postulating the structure of the chemisorbed hydrocarbon species on this surface. The saturation surface coverage for both chemisorbed molecules at 105 K is 2.5(±0.2)×1014molecules/cm2. This number is consistent with 1 hydrocarbon molecule per Si dimer site at monolayer coverage when the role of surface defects on Si(100) is considered. A di‐&sgr; bonding model for both molecules is proposed at saturation coverage.

ISSN:0021-8979    

DOI:10.1063/1.345326

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Theoretical and experimental aspects of the growth of GaAs/Al/GaAs heterostructures have been investigated. In these heterostructures the GaAs on top of the buried metal layer is grown by migration‐enhanced epitaxy (MEE) at low temperatures (200 and 400 °C) to provide a kinetic barrier to the outdiffusion of Al during superlayer growth. The crystallinity and orientation of the Al film itself deposited on (100) GaAs at ∼0 °C was studied by transmission electron diffraction, dark‐field imaging, and x‐ray diffraction measurements. It is found that the Al growth is polycrystalline with a grain size ∼60 A˚ and the preferred growth orientation is (111), which may be textured in plane but oriented out of plane. The quality of the GaAs superlayer grown on top of Al by MEE is very sensitive to the growth temperature. The layer grown at 400 °C has good structural and optical quality, but is accompanied by considerable outdiffusion of Al at the Al‐GaAs heterointerface. At 200 °C, where the interface has good structural integrity, the superlayer exhibits twinning and no luminescence is observed.

ISSN:0021-8979    

DOI:10.1063/1.345035

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For heteroepitaxial systems, such as silicon on sapphire, microtwins can usually be observed in the epitaxial layer. It has also been suggested that microtwins play a significant role in strain relief in these systems. From a knowledge of the differential volume fraction of microtwins occurring in a heteroepitaxial systems, it is possible to estimate the greatest possible strain relief due to microtwins. Measurements of the differential volume fraction of microtwins in silicon‐on‐sapphire, however, indicate that the strain relief due to microtwins cannot be greater than 0.7%, even though the lattice mismatch between silicon and sapphire is an order of magnitude larger. Therefore, if the silicon/sapphire interface is coherent, the misfit strain must be relieved by another mechanism.

ISSN:0021-8979    

DOI:10.1063/1.345036

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Zn‐doped GaxIn1−xP epilayers grown by metalorganic chemical vapor deposition have been studied in a wide range of GaP mole fraction. The Zn distribution coefficient was studied as a function of alloy composition. With a constant flow rate of diethylzinc, a decreasing net hole concentration was observed with increasing GaP mole fraction. TheI‐Vcharacteristics of Au onp‐GaxIn1−xP Schottky diodes show a deviation from an ideal thermionic behavior as the lattice mismatch increases. This deviation was analyzed in terms of the shunt resistance which decreased exponentially with the mismatch. A dominant hole trap located atEV+0.84 eV was detected by deep‐level transient spectroscopy in a Ga0.032In0.968P layer. The density of this hole trap significantly increases with increasing lattice mismatch.

ISSN:0021-8979    

DOI:10.1063/1.345011

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

At low temperatures, a subband‐gap‐light‐excited photoconductivity overshoot &Dgr;&sgr; was observed following a millisecond pulse of visible‐light excitation in hydrogenated amorphous silicon. The relative change &Dgr;&sgr;/&sgr; was attributed to an increase in the optical absorption, &Dgr;&agr;/&agr;, due to deeply trapped carriers. Both the spectral distribution of &Dgr;&agr;/&agr; and its relaxation in the annealed state A are different from those in the light‐soaked state B. Silicon dangling bonds generated by the Staebler–Wronski effect having different configuration than the thermally generated bonds are suggested as the explanation for the different behavior.

ISSN:0021-8979    

DOI:10.1063/1.345012

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A two‐layer model to explain the thickness dependence of conductivity and thermoelectric power of semiconducting thin films has been developed assuming that the film is a parallel combination of resistances of the three layers: The first is the interior ‘‘grain‐boundary’’ layer, and the other two, outer layers on opposite sides, whose conductivities are altered by the band bending (and is also affected by surface‐gas interactions). The equations obtained in this model lead to an inverse thickness dependence of both the conductivity and thermoelectric power of thin films. The model is applied to analyze the conductivity and thermoelectric variation with thickness of PbTe thin films and the parametersUg, the energy dependence of the ‘‘grain‐boundary’’ mean free pathlg, and &sgr;gthe surface conductivity, have been evaluated.

ISSN:0021-8979    

DOI:10.1063/1.345013

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have studied photocarrier generation and injection at the interface in a double‐layered organic photoconductor consisting of a charge generation layer (CGL) of vacuum‐deposited phthalocyanine film and a charge transport layer (CTL) ofp‐diethylaminobenzaldehyde‐1,1‐diphenyl hydrazone doped polymer film. The photocarrier generation efficiency in the CGL was measured by the photoacoustic method. The transport and trapping of holes in the CTL and at the CGL/CTL interface were studied by xerographic discharge measurements and time‐of‐flight photoconductivity measurements. The photogeneration efficiency in the CGL is affected by the hydrazone concentration in the CTL. At high hydrazone concentrations, the photogeneration efficiency means the quantum efficiency of photocarrier generations controlled by geminate and nongeminate recombination in the CGL. At low hydrazone concentrations, the photogeneration efficiency is affected by the injection and trapping of holes at the CGL/CTL interface. Xerographic and time‐of‐flight photoconductivity measurements show that the lifetime of holes at the CGL/CTL interface is short compared with that in the CTL and no trapping of holes occurs in the CTL. The lifetime of holes at the CGL/CTL interface decreases with increasing hydrazone concentration in the CTL. The injection efficiency of holes is determined by the competition between the trapping of holes at the CGL/CTL interface and the hopping transport of holes across the CGL/CTL interface. We discuss the influence of the hydrazone concentration in the CTL on the photocarrier generation in the CGL and the injection of holes at the CGL/CTL interface.

ISSN:0021-8979    

DOI:10.1063/1.345014

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Properties of hydrogenated amorphous silicon (a‐Si:H) prepared by glow discharge decomposition of silane with visible light illumination on a growing surface have been described. The visible light illumination during growth has resulted in smaller light‐induced changes, slightly lower photoconductivity before the prolonged illumination, lower content of bonded hydrogen, and lower ratio of the number of silicon dihydrides to that of total silicon‐hydrogen bonds. Formation of Si network and consequent structural disorder of SiSi bonds, on the other hand, has not been affected by the illumination during the growth. The improved stability against the long exposure to light can be ascribed to the lower bonded hydrogen content and the reduced density of SiH2bonds, while the structural disorder of the Si network does not have a direct relationship with the light‐induced changes.

ISSN:0021-8979    

DOI:10.1063/1.345015

出版商:AIP    

年代:1990

数据来源: AIP