摘要:

Recrystallization solvent effects on second harmonic generation (SHG) of acetylene derivatives are reported. SHG intensities of substituted diphenylacetylene recrystallized from strong polar solvents are enhanced in crystalline states.

ISSN:0003-6951    

DOI:10.1063/1.97716

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Mercury telluride is shown to have the largest known third‐order nonlinear optic susceptibility with response time in the picosecond range. At 10.6 &mgr;m andT=300 K, &khgr;(3)=1.6×10−4esu. The response time, estimated from the dispersion of &khgr;(3), is 5 ps. The effect is attributed to interband population modulation. It does not saturate below 1 MW/cm2.

ISSN:0003-6951    

DOI:10.1063/1.97717

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We apply the phase portrait analysis to semiconductor lasers with Auger recombination and extend the analysis to high modulation frequency &ohgr;m. On the two‐dimensional bifurcation diagram of modulation depth and modulation frequency, there are seven regions: digital pulsing regions, analog modulation region, period doubling regions, chaos regions, and one multiloop region. It is found that Auger recombination tends to suppress chaos for &ohgr;m<&ohgr;r, the relaxation frequency. However, for &ohgr;m>&ohgr;r, chaotic behavior becomes prominent. Furthermore, in the pulsing region, the maximum pulsation frequency is limited to a value around &ohgr;reven though &ohgr;mmay be twice or three times &ohgr;r. A normalized two‐dimensional bifurcation diagram defining the digital pulse region and the analog modulation region is presented for the purpose of locating the suitable region for analog and digital operation of semiconductor lasers.

ISSN:0003-6951    

DOI:10.1063/1.97718

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The effects of a magnetic field gradient on the energy profiles of ions extracted from an electron cyclotron resonance (ECR) microwave plasma stream are studied. The mean energy and energy dispersion of the ions strongly depend on the spatial distribution of the magnetic field strength. Ions with an energy dispersion of several eV are extracted from the plasma by the mirror field gradient application. Consequently, the magnetic field gradient, i.e., the magnetic flux profile, is one of the most important parameters in ECR microwave plasma processes.

ISSN:0003-6951    

DOI:10.1063/1.97719

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Linac‐driven free‐electron lasers, new powerful synchrotron radiation sources, and advanced high‐power microwave devices will require very bright emitters of electrons to operate efficiently. By irradiating a Cs3Sb photocathode with a frequency‐doubled, Nd:glass laser, we have obtained a very high normalized electron beam brightness of over 1011A/m2/rad2. Peak currents emitted from the 1 cm2surface in 50 ns pulses ranged up to 80 A. Measured normalized emittances were between 5 and 9 &pgr; mm mrad.

ISSN:0003-6951    

DOI:10.1063/1.97720

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A saturated bilayer of hydrogen isotopes has been formed in graphite by implanting protons and deuterons at different energies. Residual gas analysis during thermal desorption strongly suggests that hydrogen atoms recombine locally in the bulk of the damaged material and diffuse to the surface in molecular form. This model of local recombination and molecular diffusion is consistent with the predictions of the local saturation model. It also explains recent data of the low‐energy chemical erosion during hydrogen bombardment at room temperature.

ISSN:0003-6951    

DOI:10.1063/1.97670

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Certain metastable metallic crystals spontaneously vitrify upon low‐temperature annealing, as recently demonstrated for the high‐temperature solid solution of Cr and Ti. The driving force for the vitrification process can be accounted for by the concomitant decrease in lattice strain energy. Predictions for a number of binary phases are made and compared with preliminary experimental results. Spontaneous vitrification is found in the systems Co‐Nb, Cr‐Ti, Cu‐Ti, Fe‐Ti, Mn‐Ti, and Nb‐Ni.

ISSN:0003-6951    

DOI:10.1063/1.97671

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

In Ti‐Cr alloys containing both the Laves phase (ordered TiCr2) and the &bgr; phase (bcc solid solution), 1 MeV Kr+irradiation at temperatures <250 K amorphizes the Laves phase but not the &bgr; phase. The irradiation‐induced amorphous material transforms into polycrystalline &bgr; upon warming to room temperature. In contrast, irradiation at room temperature causes the &bgr; phase to grow by migration of the &bgr;/Laves interface; no change in local composition across the migrating interface is observed. The &bgr; phase also grows during prolonged irradiation at 100 K, but the velocity of the &bgr;/amorphous interface per unit calculated atomic displacement rate is more than three orders of magnitude lower than that of the &bgr;/Laves interface at room temperature. An interpretation of this new type of irradiation‐induced phase transformation is presented in terms of displacement cascade formation and dynamic recovery at the structural interface that exists between the two phases.

ISSN:0003-6951    

DOI:10.1063/1.97672

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have investigated reactively sputtered films of RuO2for possible application in very large scale integrated circuits. Sputtering yields stoichiometric ruthenium dioxide in a large window of oxygen pressures and the films are reasonably low stressed in the 10−9dyn cm−2range. The resistivity of as deposited films is 40 &mgr;&OHgr; cm. The films are excellent barriers against interdiffusion of Si and Al.

ISSN:0003-6951    

DOI:10.1063/1.97673

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Silicon wafers were implanted with 200 keV14N+ions to a dose of 0.95×101814N+cm−2at a temperature of 520 °C. These wafers were then annealed at 1405 °C for 30 min, a temperature significantly higher than that normally used (1200 °C) for annealing buried nitride, silicon‐on‐insulator (SOI) structures. Annealing leads to the formation of a well defined layer of essentially single‐crystal Si3N4containing a few low angle grain boundaries. The Si/Si3N4interfaces are abrupt, the lower one being almost planar while the upper one shows some irregularities due to fingerlike protrusions of Si3N4and has an associated region of defective silicon. The silicon overlay is single crystal with no resolvable defects making the wafers good candidates for SOI substrates.

ISSN:0003-6951    

DOI:10.1063/1.97674

出版商:AIP    

年代:1987

数据来源: AIP