摘要:

We report temperature-dependent pulsed lasing performance, internal losses, and Auger coefficients for optically pumped type-II W lasers with wavelengths in the range of 3.08–4.03 &mgr;m at room temperature. All lased to at least 360 K, and produced 1.5–5 W peak power at 300 K. Internal losses at 100 K were as low as 10 cm−1, but increased to 90–360 cm−1at 300 K. Room temperature Auger coefficients varied from5×10−28&hthinsp;cm6/sat the shortest wavelength to3×10−27&hthinsp;cm6/sat the longest. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122909

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Neutral higher silane molecules in silane radio frequency glow discharge plasmas are investigated using photoionization mass spectroscopy at various radio frequency (rf) powers and total pressures. Densities of higher silane molecules increase with rf power up to 10 W, and then decrease at 10–100 W. The reduction of the neutral higher silane molecules at high rf power suggests that these molecules contribute to the particle formation through secondary reactions in the plasma. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122897

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A detailed three-dimensional structural analysis of single-walled carbon nanotubes was carried out using a scanning tunneling microscope (STM) operated at room temperature in ambient conditions. On a microscopic scale, the images show tubes condensed in ropes as well as tubes which are separated from each other. For a single-wall nanotube rope, the outer portion is composed of highly oriented nanotubes with nearly uniform diameter and chirality. On separated nanotubes, atomically resolved images show variable chirality ranges between0°–30°,and variable diameter (1–3 nm), with no one type dominant. From STM and scanning tunneling spectroscopy measurements we confirmed the correlation between chirality and the electronic properties, namely the tuning from metallic to semiconducting. We also observed a rectifying behavior correlated with the chiral angle of25°,an important observation for nanodevices application. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122910

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The mechanical behavior of multiwalled carbon nanotube/epoxy composites was studied in both tension and compression. It was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression. In addition, it was found that the Raman peak position, indicating the strain in the carbon bonds under loading, shifts significantly under compression but not in tension. It is proposed that during load transfer to multiwalled nanotubes, only the outer layers are stressed in tension whereas all the layers respond in compression. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122911

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666&hthinsp;°C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 &mgr;m in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio, and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122912

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The combined effects of mechanical stress and surface electromigration on the dynamics of transgranular voids in passivated metallic thin films are analyzed based on self-consistent dynamical simulations. Depending on the strength of the electric and stress fields, void morphological instabilities can lead to film failure by propagation from the void surface of either faceted slits or finer-scale crack-like features. Most importantly, there exists a narrow range of applied stress for given strength of electric field over which slit formation can be inhibited completely. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122913

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant(d33)of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single-crystal quartz, thin film ZnO, and nonpiezoelectricSiO2thin films. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122914

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The MgO-dopedZrO2–TiO2ceramic pellets were studied for its humidity-sensitive electrical conduction. An equivalent circuit model has been proposed to define the humidity-sensitive electrical properties. This model is in agreement with the experimental findings. The electrical conduction is largely controlled by the intergranular impedance except at very high humidities. The impedance of the pellets showed inductive behavior in high-humidity region. This behavior can be attributed to the spherical paths adopted by charge carrier because conduction is mainly through the spherical grain surface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122915

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In situreflectance difference spectroscopy (RDS) has been performed during growth and nitrogen-doping of ZnTe thin films fabricated by molecular beam epitaxy. The doping level of the ZnTe samples can be determined by evaluating the RD spectra in the vicinity of theE1andE1+&Dgr;1transitions. RDS features in this spectral range were used to optimize online the doping performance of the N-plasma cell. Furthermore, doping-induced surface processes have been investigated, like surface saturation with activated N species and surface Fermi level pinning occurring at ambient pressure. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122916

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A procedure is presented for incorporating the results of atomistic simulations of ion–surface interactions into integrated circuit topographic simulations of ionized physical vapor deposition (PVD). Energy and angular dependent sticking probabilities for energetic Cu atoms impacting a {111} Cu surface, obtained from molecular dynamics simulations, were implemented in a simple Monte Carlo flux model. The resulting flux-averaged Cu sticking probability was found to vary significantly with position within submicron features and with the feature geometry. This illustrates the shortcomings of a constant (energy and angle independent) sticking probability model for ionized PVD. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122917

出版商:AIP    

年代:1998

数据来源: AIP