摘要:

A new type of photoacoustic microscopy is described in which the beam position, rather than the beam intensity, is modulated. It is demonstrated experimentally that the new technique provides greater detail and contrast than conventional photoacoustic microscopy.

ISSN:0003-6951    

DOI:10.1063/1.92592

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An intense, space‐charge‐neutral beam of protons (150 kV, 15 A/cm2) has been compressed from an initial diameter of 15 cm to a final diameter of 5 cm by propagating it along a magnetic field increasing from zero to 700 G in a distance of 55 cm. At the field maximum, the beam intensity is increased by a factor of 4 over the value with no field. When viewed from the beam frame, the experiment is analogous to a theta pinch with an applied field whose time derivative isv(dB/dx), wherevis the beam velocity anddB/dxis the magnetic gradient. The surface of the beam moves radially inward at approximately the velocity predicted by the snowplow model.

ISSN:0003-6951    

DOI:10.1063/1.92593

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The range of an ion can be decreased when the deposition material is heated because of the greater stopping power of free electrons over bound electrons. This suggests the possibility that a medium heated by an intense ion beam might suffer a thermal instability. It is shown that such an instability should not be important over the regimes of interest for ion beam fusion.

ISSN:0003-6951    

DOI:10.1063/1.92594

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A magnetically insulated diode with a cryogenically refrigerated anode is proposed and a prototype of such a diode is constructed. H2O ice is produced on an anode which is cooled with liquid nitrogen. A small machine, consisting of a marx generator and a blumlein line, is used to extract ion beams from the diode. Proton beams of about 50 A and 70 keV are obtained with good reproducibility. Diode electrical characteristics and the extracted beam performance are also examined.

ISSN:0003-6951    

DOI:10.1063/1.92595

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A surface plasmon that is excited on the interface separating a metal and a nonlinear semiconductor has a propagation constant that depends on the power carried by the plasmon. We present an analytic expression for the change in the propagation constant of the plasmon,K&Dgr;&bgr;, as a function of the dielectric constants of the two media, the nonlinear refractive index of the semiconductor,n2,E, and the power carried by the plasmon. We define a figure of merit,P0, which is the power required for shifting the phase of the plasmon by &pgr;/2 along a distanceS, (S= 1/2&agr;, where &agr; is the plasmon decay constant), and find the wavelength dependence ofK&Dgr;&bgr; andP0.

ISSN:0003-6951    

DOI:10.1063/1.92596

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Argon and neon crystallize in the face‐centered cubic structure (Fm3m,z= 4) at 11.5±0.5 and 47.4±0.5 kbar, respectively, at 293 K. Single‐crystal cell dimensions were obtained at 82 kbar for argon and 144 kbar for neon with high‐pressure, x‐ray diffraction techniques. The data were corrected to 0 K and fitted to a second‐order Murnaghan equation of state withV0andK0constrained to results obtained in low‐temperature experiments. No solid‐solid phase transitions are observed to the highest pressures studied.

ISSN:0003-6951    

DOI:10.1063/1.92597

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Transistor action at temperatures from 20 to 450 °C has been demonstrated forp+n−pp+bipolar structures fabricated in GaP. Improvements in the materials technology were essential to successful fabrication of these devices. The structural configuration chosen could also be used as a junction field‐effect transistor although this mode of operation was limited by the initial design to lower operating temperatures. While present device characteristics are restricted by ohmic contact resistance, this does not appear to be a fundamental limitation. These results demonstrate that GaP is a good materials candidate in which to base a technology for active electronic components operated at high temperatures.

ISSN:0003-6951    

DOI:10.1063/1.92598

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

This letter presents a modified version of the grain boundary barrier model for polycrystalline semiconductors which takes into account the carrier transport in the bulk of the grain and the dynamic process of capture and release of free carriers by the grain boundary traps.

ISSN:0003-6951    

DOI:10.1063/1.92599

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A composite metallization of Al over doped poly‐Si should exhibit superior electromigration resistance, since even after the Al develops an open circuit, the poly‐Si would be expected to provide electrical continuity. However, results indicate that poly‐Si reduces the lifetime of Al by a ×2 and a further decrease occurs over stepped topographies. Thus, while electron beam evaporated Al/poly‐Si exhibits acceptable lifetimes, induction‐source Al/poly‐Si may be only marginal in this regard. Failures occur predominantly at steps by nonuniform grain boundary diffusion in Al, until the metal opens up. This followed by the electromigration of Si into Al and localized melting.

ISSN:0003-6951    

DOI:10.1063/1.92600

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Secondary ion mass spectrometry was used to measure the18O profiles in thermally grown SiO2which had been treated in H2 18O steam. The oxygen isotope exchange between the water and the network proceeds rapidly at 800 °C, completely exchanging a 180‐nm film in ∼20 min. Even at 400 and 600 °C, where negligible Si oxidation occurs, the network oxygen can be completely isotopically exchanged. The exchange profiles are analyzed in terms of the competing reactions involving water molecules and the SiO2network. Similar measurements of the deuterium (D) profiles in D2O‐treated films are consistent with diffusion of molecular water and its reaction with the network to transport both hydrogen and oxygen through the thermal oxide. Our results are compared to related studies which used18O nuclear resonance analysis.

ISSN:0003-6951    

DOI:10.1063/1.92601

出版商:AIP    

年代:1981

数据来源: AIP