摘要:

An aligned nematic droplet in the axial configuration is modeled as a hollow spheric scatterer for studying its small angle light scattering characters. When the thickness of the shell is reduced by an external field, calculations by anomalous diffraction approximation suggest that scattering intensity would decrease and scattering peak would drift to a smaller angle. Measured angular scattering intensities show good agreement with calculations. As the shell part originates from anchoring of the nematic molecules to the surrounding medium, angular scattering intensity can be associated with correlation length. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363689

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We use molecular dynamics techniques to study the ion beam induced enhancement in the growth rate of microcrystals embedded in an amorphous silicon matrix. The influence of the ion beam on the amorphous‐to‐crystal transformation was separated into thermal annealing effects and defect production effects. Thermal effects were simulated by heating the sample above the amorphous melting point, and damage induced effects by introducing several low energy recoils in the amorphous matrix directed at the crystalline grain. In both cases, the growth rate of the microcrystals is enhanced several orders of magnitude with respect to the pure thermal process, in agreement with experimental results. The dynamics of the crystallization process and the defect structures generated during the growth were analyzed and will be discussed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363690

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An amorphous Ge‐Au(a‐Ge‐Au) film prepared by vacuum deposition was studiedinsituand irradiated by an electron beam in a transmission electron microscope. The amorphous Ge‐Au film can be crystallized rapidly and locally by electron beam irradiation, forming polycrystalline metastable Ge0.4Au0.6tetragonal phase and then decomposing to polycrystalline Ge and polycrystalline Au at increased irradiation dose. The results suggest that the crystallization ofa‐GeAu film, the formation of Ge0.4Au0.6and the decomposition of the metastable Ge0.4Au0.6are dependent on the temperature rise of the irradiation process. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363691

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A sample of Nd2Fe17Nxpreviously studied has been remeasured with higher‐resolution powder neutron diffraction. Rietveld analysis confirms the existence of two values ofx. The higherxcorresponds to nearly full occupation of the octahedral 9esite, while the lower value corresponds to partial occupancy of both the octahedral and tetrahedral 18gsites by nitrogen. The lattice changes for both compositions have been carefully examined. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363692

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Gold diffusion experiments were performed in three types of polycrystalline silicon over the temperature range 551–1265 °C by using the radiotracer195Au and the serial sectioning technique. Depending on temperature, material structure, and diffusion time, different types of profiles were obtained, some of them being noninterpretable within the framework of classical solutions of Fick’s equations in the presence of grain boundaries. In contrast, all these experimental profiles were successfully analyzed by using a new diffusion model applicable to host material/impurity systems revealing strong segregation effects and a negligible diffusion flux along the extended defects. At temperatures higher than about 1100 °C, effective diffusion coefficients slightly lower than true lattice diffusion coefficients previously reported in the literature were measured. Decreasing the temperature, the effective Au diffusivity depends on the structure of the samples, which leads to different Arrhenius plots exhibiting a downward curvature. A gold segregation enthalpy of about 141 kJ mol−1was estimated from the observed diffusion behavior. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363712

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

While the same atomic mechanism is usually assumed in both viscous flow and diffusion in a liquid, viscous flow is found much faster (by many orders of magnitude) in all situations studied where the mass transfer is caused by pressure gradients. A detailed study shows that Fick’s law must be modified for self‐diffusion in liquids. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363693

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Defects, notably interstitial impurities, are responsible for degradation of resonator performance with time. In order to study the mobility of ionic impurities, we have measured thermionic currents as a function of temperature by the thermally stimulated depolarization (TSD) method. We have observed several current maxima; each peak is due to the displacement of an impurity family from a given site and is characterized by its activation energy. Making impedance measurements to complete these results, we find energies of about 1 eV. We have studied quartz crystals doped with a given impurity in order to identify the nature of the impurities responsible for some current peaks. This study confirms that the TSD method is very sensitive. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363694

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We studied the recombination‐enhanced Fe atom jump between the first (1st) and second (2nd) neighbor sites of Fe–Al and Fe–B pairs in Si. We first annealed specimens at 80 °C to generate Fe–acceptor pairs after doping of Fe. Concentrations of the 1st and 2nd neighbor Fe–acceptor pairs were determined by electron‐spin‐resonance (ESR) measurement after annealing at around 150 K under optical excitation. The concentration of the 1st neighbor pair was decreased and that of the 2nd neighbor pair was increased by the above annealing. Activation energy for the above changes was about 0.11 eV in the case of the Fe–Al pair. This is much smaller than that (0.8 eV) of thermal annealing alone. In the case of the Fe–B pair, the ESR signal of the 2nd neighbor pair could be detected due to annealing at around 160 K under optical excitation. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363695

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

X‐ray diffraction has been used to characterize the heteroepitaxial growth of indium formed at the interfaces between ZnO thin film and InP monocrystalline substrates. The In formation was induced by a thermal degradation of InP during annealing in the range of 400–700 °C for 3 min. The results prove that the evolution of the degradation is controlled by the decomposition of close‐packed InP{111} planes, while the polar character of these planes plays a very important role. Moreover, for all four employed orientations of InP substrates [namely (111)A, (111)B, (110) and (100)], In is found to grow (101) on InP{111} planes. On an InP{111} interface plane, In crystallites can occur in six possible orientations characterized by a condition In⟨100⟩∥InP⟨110⟩. To estimate a mismatch of the heteroepitaxy, a geometrical model of the atomic arrangement at In(101)‐InP(111) interface is given. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363696

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The influence of starting surface topography on the nucleation and growth of epitaxial silicide layers was investigated. CoSi2layers were grown via the template technique on one‐dimensionally patterned Si(100) substrates. These substrates contained mesa stripes, running parallel to Si[011], and exhibited either a number of Si {hkl} facets, or ‘‘smoothly varying’’ sinusoidal profiles. Conventional plan view and high resolution cross section transmission electron microscopy showed that the orientation and morphology of the CoSi2grains depend on the angle (&thgr;) between the CoSi2/Si interface normal and Si(100). CoSi2(100) grains nucleated on mesa tops and trench bottoms, where &thgr;<5°, and formed atomically sharp interfaces. CoSi2(110) and CoSi2(221) grains nucleated along sidewalls of the mesa structures, in regions where 5°<&thgr;<11° and &thgr;≳5°, respectively. CoSi2(110) grains formed highly stepped interfaces with the substrate which were punctuated by step bunches at the grain boundary/substrate triple points. CoSi2(221) grains formed rough interfaces with the substrate which were punctuated by facets andB‐type silicide/substrate interfaces along Si{111} planes. Analysis of these data suggests that nucleation of CoSi2(110) grains is associated with the presence of double height steps and step bunches with small surface misorientation, and that nucleation of CoSi2(221) grains is associated with Si{111} facets, Si{311} facets, and step bunches with larger surface misorientation. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363697

出版商:AIP    

年代:1996

数据来源: AIP