摘要:

The luminance‐applied voltage hysteresis characteristic, so‐called memory effect, has been found in the SrS:Ce,K blue‐emitting electroluminescent thin‐film device. The hysteresis voltage width is about 38 V with 1 kHz pulse drive. The origin of the memory effect is attributable to native defects of the SrS phosphors.

ISSN:0003-6951    

DOI:10.1063/1.97689

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Energy amplification of short pulses in the presence of distributed absorption is analyzed and discussed. A short pulse is defined as a pulse length that is much shorter than the lasing state lifetime. It is shown that the energy density of a short pulse cannot be amplified indefinitely in the presence of nonsaturable absorption. In an active medium having a small signal gaing0and a nonsaturable absorption &agr;, the maximum attainable energy density is (Esatg0/&agr;), whereEsatis the medium saturation energy. High‐energy densities are obtained at the expense of the extraction efficiency. An amplifier design can be optimized by choosing the appropriate parameters such as small signal gain and active medium gain length.

ISSN:0003-6951    

DOI:10.1063/1.97690

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Femtosecond carrier dynamics in GaAs and Al0.3Ga0.7As are investigated using pump probe measurements of transient absorption saturation. Pulses of 35 fs duration are used both to excite carriers and to investigate their subsequent scattering out of their initial optically excited states. A two‐component ultrafast relaxation is observed. In GaAs the initial rapid relaxation occurs on a time scale of 10–35 fs. Measurements performed in Al0.3Ga0.7As indicate that this initial process slows significantly to 130–170 fs for increasing band gap.

ISSN:0003-6951    

DOI:10.1063/1.97691

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Falling‐ball rheometry is used to study a suspension (volume fraction solids=0.05) of large, neutrally buoyant rods (length=3.175 cm, diameter=0.154 cm) in a viscous Newtonian liquid. We find that all sizes of balls studied (0.65 cm ≤ diameter ≤1.90 cm) experience the same continuum that is characterized by a single viscosity which we have measured to be 2.41 times greater than that of the pure suspending liquid. The viscosity increase due to the presence of the rods is over 12 times greater than that observed for a suspension of uniform spheres having the same volume fraction. The results are free of any flow induced clustering and orientation effects and are in reasonable agreement with theoretical predictions for randomly oriented rods.

ISSN:0003-6951    

DOI:10.1063/1.98244

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The effect of Si on the reaction between Al and Al‐2% Si films with the transition metal Ti in bilayer structures is studied by the resistivity measurements on samples isothermally annealed in the temperature range of 400–450 °C. The change in the resistivity of the structures is correlated to the rate of formation of an intermetallic compound TiAl3due to the interaction between Ti and Al. It is found that the reaction rate of the intermetallic compound formation is reduced by a factor of 3 for Ti/AlSi compared with the Ti/Al bilayer structures. The growth mechanism in both the cases is indicated to be diffusion limited. The activation energy for the Ti/AlSi increases to 2.2 eV from 1.7 eV for the Ti/Al structure.

ISSN:0003-6951    

DOI:10.1063/1.97692

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The mechanical properties of the diamondlike coatings deposited with mass‐separated C+, CH+3, CH+4, and C2H+2ion beams have been compared. The hardness, abrasive wear resistance, and adhesion of the coatings prepared with the C+ion beam were superior to those of the coatings prepared with other ions. The most serious drawback of the films prepared with hydrocarbon beams was their brittleness and weak adhesion.

ISSN:0003-6951    

DOI:10.1063/1.97693

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have used a unique sample configuration consisting of thin, epitaxial films of Ge sandwiched within a Si(100) lattice to explore the conditions for statistical equilibrium in particle channeling. Indications of nonequilibrium came about from a strong asymmetry in the off‐normal angular scans. We find the depth necessary to achieve statistical equilibrium to be ∼2200 A˚ for 1.8 MeV He particle channeling along the Si⟨110⟩ direction. This measurement provides a useful guide for the interpretation of channeling experiments in a variety of near‐surface applications.

ISSN:0003-6951    

DOI:10.1063/1.97694

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Nitridation and oxidation of titanium and iron immersed in liquid N2, NH3, or H2O are achieved by pulsed excimer laser treatment. Rutherford backscattering spectrometry reveals that significant quantities of nitrogen and oxygen can be incorporated in the metal matrices over a depth scale of several thousand angstroms. X‐ray diffraction gives evidence for compound formation and scanning electron microscopy for large stress in the surface layer. The process is viewed as chemical reactive solute incorporation in the metal surface layer in its laser induced liquid state, followed by compound formation.

ISSN:0003-6951    

DOI:10.1063/1.98248

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

InGaAsP/InP optical switches have been fabricated which use a carrier induced refractive index change. Switching has been achieved with a power isolation of 20.5 dB in a 1‐mm‐long device in multimode operation. This is a promising new step toward making optical integrated circuits.

ISSN:0003-6951    

DOI:10.1063/1.97695

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

It has been determined that the incorporation of carbon into GaAs crystals grown by the liquid encapsulated Czochralski method occurs as the result of a reaction between the GaAs melt and gaseous oxides of carbon, rather than carbon particles. The incorporation occurs during growth as well as during synthesis. The incorporation of carbon was particularly large when a commercially available large puller was used because of the greater number of carbon components in the hot zone which act as sources. Crystals with a low carbon concentration of 1×1015cm−3have been successfully grown by employing pyrolytic boron nitride coated graphite components in the large puller.

ISSN:0003-6951    

DOI:10.1063/1.97642

出版商:AIP    

年代:1987

数据来源: AIP