摘要:

Sum-frequency mixing in neodymium-dopedYAl3(BO3)4of its fundamental laser line at 1062 nm and the pump light from a tunable Ti:sapphire laser has been used to generate blue radiation from 435 to 465 nm in an end-pumped configuration. In nonoptimal preliminary experiments 22 &mgr;W at 458 nm was obtained out of 200 mW absorbed power at 807 nm. Nd:YAB, therefore, emerges as a promising laser material for diode-pumped solid-state lasers in the blue spectral region. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122854

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have investigated the MeV bremsstrahlung which is emitted when fast electrons generated by the interaction of 200 mJ, 130 fs Ti:sapphire laser pulses with a preformed plasma penetrate into a solid target. Employing different targets the dependence of the&ggr;-rayspectrum on the atomic number was studied. We detected single &ggr; photons with an energy up to 2.5 MeV and found a maximum conversion efficiency of the laser energy into MeV bremsstrahlung of4×10−6.Data analysis using a Monte Carlo code revealed a fast-electron temperature of 0.9 MeV.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122855

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The viscosity and flow stress of a bulkPd40Ni10Cu30P20alloy glass near the glass transition were measured as a function of temperature and strain rate under compression. The steady-state viscosity of the glass for a given temperature remains constant at low strain rate, then decreases by many orders of magnitude above a critical strain rate. A master curve in term of the viscosity ratio&eegr;/&eegr;Nand the product&eegr;N&egr;˙has been constructed, where &eegr; and&eegr;Nare, respectively, the steady-state viscosity and Newtonian viscosity, and&egr;˙is the strain rate. The flow stress also can be represented in terms of the product&eegr;N&egr;˙.The master curves are fitted with a simple stress relaxation of the form1−exp[−t/&lgr;]witht=&egr;˙−1.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122856

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A thin (∼2 nmthick) amorphous diamond coating was prepared on single crystal silicon tip arrays by using a filtered vacuum arc plasma deposition technique. The coating has a microscopically uniform morphology. As compared to uncoated tips, the electron emission of the coated tip arrays is enhanced, showing an increase in the total current, lower turn-on field and a lower-slope Fowler–Nordheim plot. We propose that field-emitted electrons could tunnel through such a thin coating with few scattering events. It is shown that the low potential barrier at the interface is the major cause of the enhancing effects instead of the negative surface electron affinity of the coating. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122857

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Carbon nitride particles of nm size were prepared in an induction thermal plasma treatment of carbon powder including a small amount of nitrogen. Relatively large ones of about 5 nm in diameter are mostly in a dodecahedral shape. The structure was analyzed by high-resolution transmission electron microscopy and electron energy-loss spectroscopy to be a cubicC3N4,which had been predicted by a first-principles calculation as a substance with the highest bulk modulus. The lattice parameter is, however, rather large(a=0.582nm) as compared to the prediction. N-deficient planar defects are included in some of the particles. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122858

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

PolycrystallineSrBi2Ta2O9(SBT) ferroelectric thin films were synthesized onPt/Ti/SiO2/Sisubstrates by metalorganic decomposition. Electric measurements demonstrate that the polarization decay increases with increasing the write/read voltage within the first second. This could be attributed to the depolarization fields, which increases with increasing the retained polarization. However, we found that the polarization loss is insignificant with different write/read voltages over a range of 1–30 000 S. Furthermore, experiment indicates that there is weak pinning of domain walls existing in SBT, which plays an important role for SBT thin film over a range of 1–30 000 S with a low write/read voltage. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.122859

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effect of compression on grain growth in Al and Al(Cu) films on oxidized Si substrates has been studied. Samples were compressed in a uniaxial press during annealing at 400 °C, and then examined using focused ion beam imaging. It was found that the compressed regions had a final grain size roughly a factor of 3 larger than in the uncompressed regions. This behavior is interpreted as due to a decrease in grain boundary grooving and the pinning forces associated with them, thus allowing enhanced grain growth. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122860

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The influence of bias voltage on the quality of scanning tunneling microscopy images of carbon nanotube “rafts” was investigated in the range from −1 to 1 V in combination with scanning tunneling spectroscopy (STS) measurements. While for positive tip polarity only a slight voltage dependence was found in the image quality, for negative polarity a strong increase of the noise was observed with increasing voltage. STS showed that, for negative tip polarity, the tunneling current may be different in different locations by several orders of magnitude. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122861

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Doped alkaline–bismuth–titanate perovskite single crystals have been grown in ferroelectric phases with high piezoelectric actuation. Rhombohedral-phaseNa1/2Bi1/2TiO3–BaTiO3crystals exhibit up to 0.25&percent; free strain with low hysteresis along the cubic ⟨001⟩ direction(d33∼450 pC/N).Tetragonal phase crystals exhibit free strains as high as 0.85&percent; with greater hysteresis characteristic of domain switching; low fieldd33exceeds 500 pC/N. Strain energy densities exceed those of optimized polycrystalline lead perovskites, and actuation capability is retained at compressive stresses >100 MPa. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122862

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In this letter we examine an influence of surface morphology on yellow and edge emissions in wurtzite phase GaN. Our cathodoluminescence measurements show that the yellow emission does not correlate with the surface morphology, but simultaneously the “edge” emission shows very strong spatial fluctuations. The observed effect is attributed to granular structures in GaN films and enhancement of the yellow emission in the interface region. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122863

出版商:AIP    

年代:1998

数据来源: AIP