摘要:

An electro-optical element based on antiferroelectric liquid crystal (AFLC) has been prepared by photopolymerization-induced anisotropic phase separation of a solution of an AFLC and a prepolymer. It consists of two adjacent layers, one comprised of the isotropic polymer and the other of the AFLC aligned by surface treatment of the adjacent substrate. The electro-optical properties show that these devices are either optically monostable or multistable (at zero field) with maximum memory angle of ∼15°. A qualitative model to describe the origin of memory in these AFLC/polymer composites is discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122721

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The achievement of high-quality continuous polycrystalline silicon (poly-Si) layers onto glass substrates by using aluminum-induced crystallization is reported. The crystallization behavior of dc sputtered amorphous silicon on glass induced by an Al interface layer has been investigated above and below the eutectic temperature of 577 °C. Secondary electron micrographs in combination with energy-dispersive x-ray microanalysis show that annealing below this temperature leads to the juxtaposed Al and Si layers exchanging places. The newly formed poly-Si layer is fully crystallized and of good crystalline quality, according to Raman spectroscopy and transmission electron microscopy investigations. At 500 °C, the time needed to crystallize a 500-nm-thick Si layer is as short as 30 min. By annealing above the eutectic temperatures, layer exchange is not as pronounced and the newly formed Al layer is found to contain a network of crystallized Si. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122722

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Polarized Raman scattering by phonons is used to characterize thin films prepared by laser ablation ofLa1−xCaxMnO3targets. It was found that, in the temperature range from 6 to 300 K, phonon spectra ofLa0.7Ca0.3MnO3films exhibit observable differences from those in bulk materials (microcrystalline ceramics and single crystals). A significant difference was found in the spectra of “as-grown” films compared to those annealed in oxygen at 800 °C. The observed Raman peaks and their linewidths exhibit an irregular temperature dependence nearTc.A correlation of Raman data with magnetization of the sample was also found. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122723

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Diffusion data for amorphous binary alloys are scarce in the literature. There are no data available for the diffusion of Al in Al–Pt amorphous phase known to the authors. High-temperature successive deposition of components was used in the present experiments to reveal the elementary processes of reactive diffusion forming the metastable amorphous phase and to determine the diffusion coefficient of Al in this phase:D(&agr;)=(1.2±0.4)×10−10×exp[−(6.9±0.1)×104J&hthinsp;mol−1/RT]m2&hthinsp;s−1.This value, taken from thin film experiments, can be considered as a good approximation to the bulk diffusion coefficient. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122724

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Gold dots of 2.5 nm mean diameter and 0.8 nm standard deviation have been fabricated successfully on chromium oxide(CrOx)thin films. TheCrOxthin films were deposited on Si substrates by sputtering and gold dots were subsequently deposited by a retarding-field single ion deposition (RSID) technique. The formation of gold dots has been investigated systematically with landing energies from 100 to 900 eV and doses from 10 to40 C/m2.The dot diameter and density could be controlled by varying the landing energy and dose of gold ions arriving on the surface. The formation of single electron devices, quantum dots, nanopillars, and other nanoscale device structures is proposed using the RSID technique. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122725

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The intrinsic stresses have been investigated in detail in particular diamondlike carbon films prepared by chemical vapor deposition assisted by electron cyclotron resonance plasma, as a function of the substrate bias and sample thickness in relation with the H content and bonding. Combined infrared absorption, elastic recoil detection analysis, and residual stress measurements are used to fully characterize the films in their as deposited state. The results indicate clearly that both the low and high biased samples exhibit compressive stresses. The stresses are found to be higher in the high biased films and are affected not only by the [H]/[C] ratio but also by the C–H and C–C volumetric distortions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122726

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Images of nanometer-scale ferroelectric domains inBaxSr1−xTiO3thin films are obtained with 30 Å spatial resolution using apertureless near-field scanning optical microscopy (ANSOM). The images exhibit inhomogeneities in the ferroelectric polarization over the smallest scales that can be observed, and are largely uncorrelated with topographic features. The application of an in-plane static electric field causes domain reorientation and domain-wall motion over distances as small as 40 Å. These results demonstrate the promise of ANSOM for imaging near-atomic-scale polarization fluctuations in ferroelectric materials. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122727

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report on the incorporation of In during growth ofInxGa1−xNby molecular beam epitaxy under varying In/Ga flux ratios and with different film thicknesses. The incorporation efficiency studied by energy dispersive x-ray microanalysis, high-resolution x-ray diffraction and photoluminescence spectroscopy is strongly affected by the chosen fluxes of Ga and N and is limited by the excess of nitrogen compared to gallium. Furthermore, thick films exhibit a decrease of the In content in growth direction. The behavior can be explained by considering the different stabilities of the two binary compounds InN and GaN. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.122728

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In addition to the persistent photoconductivity (PPC) attributed toDXcenters in GaAs delta-doped with Si, a weak PPC (WPPC) with a PPC carrier density independent of Si-doping concentration has been generally reported at ambient atmosphere, but the nature of the deep states responsible has not been elucidated. Here, we present the results of a detailed study of the WPPC in &dgr;-GaAs:Si at low-doping densities,NSi≈1–3×1012&hthinsp;cm−2,and ambient pressure. It is concluded that the WPPC does not arise fromDXcenters but from another deep defect, which isDX-like in the sense that it can be metastably excited. The presence of two distinctDX-like states is apparent from two separate annealing temperatures of the PPC,Ta≈50 KandTb≈230 K;to the best of our knowledge, the latter is the highest annealing temperature observed in the AlGaAs:Si system. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122729

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Optical properties of zincblende structuredZnxCd1−xSeepilayer grown on InP by metal organic chemical vapor phase deposition at temperatures of 360, 400, and 440 °C are investigated with low temperature cathodoluminescence spectroscopy (CL). Both near band gap and deep level emissions are found for the samples grown at 400 °C and above, but deep level emissions are absent for the sample grown at 360 °C. We conclude that the growth temperature should be kept below the temperature at which InP begins to decompose and diffusion of III–V constituents into the epilayer occurs. Evidence of this diffusion comes from an analysis of depth resolved CL studies, which shows that the deep level emissions occur mainly at the epilayer/substrate interface. By monitoring the ratio of the intensity of the deep level emissions to that of the near band emissions, we find that this ratio is larger for samples grown at high temperatures than those at low temperatures. Indium diffusion from the substrate into the epilayer is most likely the source of these deep levels. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122730

出版商:AIP    

年代:1998

数据来源: AIP