摘要:

We report fabrication of single layer poly(p-phenylene vinylene) (PPV) light emitting diodes with low turn-on voltages by chemical vapor deposition of dihalop-xylenes. Devices made from dibromop-xylene exhibit turn-on fields of2×106 V/cm,which is in good agreement with solution processed PPV devices. Devices made from dichlorop-xylene, however, have significantly lower turn-on fields of6.5×105 V/cm.The electroluminescent output of bilayer PPV/tris (8-hydroxyquinoline) aluminum devices made from the two monomers suggests that the chlorine based polymer may have improved electron transport characteristics compared to solution processed polymer, which is tentatively attributed to residual chlorine from the thermal conversion process. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119351

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the measurement of nonlinear refraction in ion-doped solids with a method that combines the single-beamZ-scan technique and a Fourier analysis of the transmittance time evolution. The laser beam is modulated at a frequencyfand the Fourier components atfand2fare shown to be related, respectively, to linear and nonlinear refractions. Their ratio is used to eliminate spurious linear effects as a way of increasing the sensitivity of the measurement. With this method we are able to measure nonlinear phase changes of a few tens of mrad, corresponding to wave front distortions smaller than&lgr;/105.Moreover, the technique can discriminate nonlinear processes with different relaxation times. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119352

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The third-order optical nonlinearity&khgr;(3)of nanometer-sized CdO with different interfacial environments has been measured using theZ-scan technique. The real and imaginary parts of&khgr;(3)at 800 nm have been determined to be:−1.55×10−16 m2/Wand 0.91 cm/GW for CdO–CTAB (cetyltrimethyl ammonium bromide) organosol, and−6.97×10−16 m2/Wand 8.64 cm/GW for CdO–DBS (dodecylbenzene sulfonate) organosol. Origins of the optical nonlinearity and the effects of the interfacial conditions have been discussed. The optical Stark effect (OSE) and surface trapped states are the possible origins of the observed optical nonlinearity. The possible enhancement of optical nonlinearity of nanoparticles by intentional interfacial modification is suggested. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120424

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The extraordinary wave (X wave) was found to contribute to the uniformity of an electron cyclotron resonance (ECR) plasma whose electron density is about1–2×1017 m−3.The X wave propagated radially in the plasma both before and after the ECR point. The electron density jump occurred when the electron density was equal to the cutoff density of the X wave at the ECR point. Upon increasing the electron density, only the whistler wave propagated in a high density plasma of about1018 m−3.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120416

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The deposition of thin alternating layers of Cu and Nb on Si(100) substrates has been studied by transmission electron microscopy as a function of layer thickness. For layer thickness above 25 Å, there is a strong texture orientation relationship with the close packed planes of fcc Cu parallel to close packed planes of bcc Nb, forming the so-called “Kurdjumov-Sachs” orientation relationship. However, at thicknesses of under 12 Å, the Cu is constrained to grow as a slightly distorted bcc structure. It is thought that, when it reaches a critical thickness between 12 and 20 Å, the bcc Cu loses coherency and transforms martensitically to the fcc phase, resulting in the observed Kurdjumov–Sachs orientation relationship. Electron energy loss spectroscopy observations indicate a difference of 2 eV in theL3edge suggesting that the Fermi energy is lower in the constrained bcc form of Cu than in the equilibrium fcc structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119611

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The density of silicon islands trapped in buriedSiO2layers produced by the implantation of oxygen into (001)Si substrates is monitored by atomic force microscopy for the oxygen dose range just above that required for continuous oxide formation. In addition to an exponential increase in the Si island density with oxygen dose, the regularly shaped remnants of anSiO2phase with a reduced HF etch rate were found. The formation of this additional oxide phase as a result of enhanced internal pressure inside the Si crystal is proposed to account for the retention of Si islands in the buried oxide. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119353

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have used an optical pump-and-probe technique to measure the temperature dependence of the thermal conductivity,&kgr;(T),of isotopically pure Si. The sample was made from 99.7&percent;28Siby liquid phase epitaxy. Measurements were performed over the temperature range of 100–375 K. We found an increase in the thermal conductivity of isotopically pure Si, as compared to Si of natural isotopic abundance, throughout the entire temperature range. The results were theoretically reproduced by appropriately scaling the parameters used recently to fit the thermal conductivity of Ge samples with different isotopic compositions. A maximum in&kgr;(T)of∼4×104 W m−1 K−1is predicted for28SiatT≃33 K.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119384

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

With an undulator-based synchrotron source and a tunable x-ray monochromator, we produce an x-ray beam with a flux of4×108 photons/sin an energy bandwidth of920±110 &mgr;eV(&Dgr;E/E≈6.2×10−8)at a photon energy of 14.4 keV. The tunability of the monochromator allows for a measurement of lattice excitations in &agr;-Fe using the technique of inelastic nuclear resonant scattering from57Fe.The phonon density-of-states are extracted from the measurement and compared to the calculated phonon density-of-states derived from neutron-scattering measurements. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120448

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In cooperation with Zeiss/LEO GmbH, a monoenergetic positron source has been integrated in the electron optical system of a scanning electron microscope by help of a magnetic prism. The electron optics serves both to image the specimen with electrons and to form a positron microbeam that allows local positron-annihilation measurements with a resolution in the micron range. The fatigue damage profile along the cross section of a copper plate after a three-point bending test has been investigated. The obtainedS-parameter profile coincides well with the expected fatigue damage distribution. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120451

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the observation of the influence of light polarization on the photocrystallization process and on the properties of crystallized films. Irradiation with linearly polarized He–Ne laser light results in the preparation of polycrystalline films with strong optical anisotropy (dichroism), the sign of which is determined by the direction of the electrical vector of light. The results obtained allow one to select from previously proposed mechanisms of photocrystallization. Large values of photoinduced dichroism in the films studied can be interesting for different applications of photoinduced anisotropy. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119354

出版商:AIP    

年代:1997

数据来源: AIP