摘要:

The energy distributions of ions ablated from silver in vacuum have been measuredin situfor pulsed laser irradiation at 355 nm. We have determined the energy spectra for directions ranging from 5° to 75° with respect to the normal in the intensity range from 100 to 400MW/cm2.At the highest intensity and for angles close to the normal, the highest ion energy measured exceeds 500 eV. However, the energy distributions are shifted strongly towards low energies with increasing angle. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121197

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using polarized infrared (IR) absorption, we have investigated the surface anisotropy of a poly [4, 4′-oxydiphenylene-pyromellitimide] (PMDA-ODA) film that arises from anisotropic decomposition of the polyimide chain during irradiation with linearly polarized ultraviolet (LPUV) light. To monitor the surface anisotropy, we designed the sample structure so that the polyimide films decomposed uniformly over the entire film thickness. The surface anisotropy has a maximum at an irradiation energy of 105J/cm2.For PMDA-ODA, the maximum surface anisotropy is significantly smaller than the surface anisotropy generated by rubbing. By analyzing the irradiation energy dependence of an IR absorption band, we found that the decomposition rate of the polyimide chain oriented parallel to the polarization direction of the LPUV light is greater only by ∼23&percent; than that oriented perpendicular to it. This is the reason for the small surface anisotropy induced by the LPUV light irradiation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121198

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Silicon nanowires have been synthesized in high yield and high purity by using a high-temperature laser-ablation method with growth rates ranging from 10 to 80 &mgr;m/h. Transmission electron microscopic investigation shows that the nanowires are crystalline Si, and have diameters ranging from 3 to 43 nm and length up to a few hundreds microns. Twins and stacking faults have been observed in the Si core of the nanowires. The lattice structure and constant of the nanowires as determined from x-ray diffraction (XRD) are nearly identical to those of bulk Si, although the relative XRD peak intensities are different from those of randomly oriented Si crystallites. Raman scattering from the nanowires shows an asymmetric peak at the same position as that of bulk crystalline silicon. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121199

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The degradation of cathodoluminescent (CL) brightness under prolonged electron-beam excitation of phosphors has been identified as one of the outstanding critical issues for flat-panel field-emission displays. In this letter, we have demonstrated that aTaSi2coating onY2O2S:Eu3+phosphors substantially inhibits the cathodoluminescent degradation characteristics without reducing its efficiency. The coating was deposited by pulsed laser deposition ofTaSi2targets onto a fluidized bed containing phosphor particles. Cathodoluminescent degradation experiments conducted at 2 keV and at150 &mgr;A/cm2,showed that the CL brightness decreased by more than 50&percent; after a Coulomb load of15 C/cm2on the uncoated material. In contrast, theTaSi2-coated phosphor powders showed much less degradation, with CL brightness only decreasing by approximately 12&percent; after electron irradiation with the same dose. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121195

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We demonstrate the utilization of various transition metals in a biologically derived, nanometer-scale patterning process. This process created large arrays of nanometer-scale dots (nanodot arrays) with several of these metals. The correlation between nanodot array formation and the interaction energies between metal atoms, other metals atoms, and the surface of the sample was explored. The behavior of the metal films was then investigated with the aid of a Monte Carlo solid-on-solid simulation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121200

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Graphite samples are heated in a diamond anvil cell with aCO2laser above 11 GPa. A light transparent phase has appeared after heating, which is quenchable at ambient conditions. The Raman spectrum shows that the phase is a fine-grained cubic diamond. Images by a high resolution transmission electron microscope indicate that the diamond has twins and stacking faults of nanometer size. The electron diffraction pattern shows that the stacking fault cannot be explained by a diamond polytype such as a hexagonal diamond. The cathodoluminescence pattern exhibits the “band-A” emission, which is derived from the defects of the cubic diamond. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.121201

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In this letter, we study Ta/parylene-F (PA–F) buried interfaces using x-ray photoelectron spectroscopy. We found that the Ta–F bond was formed at the Ta/PA–F interface after depositing a layer of thin Ta film(<50 Å).For theAr+orO2plasma pretreated PA–F surface, in addition to the Ta–F bond, a Ta–C bond was observed at the buried interface after Ta metallization. The Ta–C bond may be responsible for the enhancement of Ta/PA–F adhesion. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121202

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We observed strong correlation between optical properties and transport properties in GaN. Both the intensity and the energy of near-band edge photoluminescence (PL) peak in GaN:Si vary with its mobility. Such behavior has been explained by the potential fluctuation associated with the inhomogeneous impurities or local defects, leading to the space-charge scattering of carriers and the redshift of the PL line. We also discuss the strain relaxation in GaN:Si. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121203

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Different conduction behavior is observed in nonstoichiometric (NS) molecular-beam epitaxial GaAs grown at 200 °C below and above the critical thickness. In the low-field Ohmic region only the monocrystalline part of the layer contributes to the room-temperature resistivity, but at higher temperatures the resistivity scales with the total layer thickness. In NS GaAs grown above the critical thickness, a superlinearJ–Vn(n=2–3)dependence is found at intermediate fields. The prebreakdown voltage is proportional to the total thickness. This indicates that different defects control the electrical properties of the polycrystalline and monocrystalline parts of the NS GaAs. These results can be useful in the design of NS GaAs based devices, which operate at higher temperature and/or higher electric fields. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121204

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The charge-carrier transport mechanism in the organic semiconductor pentacene is explored using thin-film transistor structures. The variation of the field-effect mobility with temperature differs from sample to sample, ranging from thermally activated to temperature-independent behavior. This result excludes thermally activated hopping as the fundamental transport mechanism in pentacene thin films, and suggests that traps and/or contact effects may strongly influence the observed characteristics. These results also indicate that field-effect transistors may not be appropriate vehicles for illuminating basic transport mechanisms in organic materials. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121205

出版商:AIP    

年代:1998

数据来源: AIP