摘要:

This letter reports the observation of one‐ and two‐dimensional amplified spontaneous emission of F+3color centers in a LiF crystal and a measurement of its optical gain coefficient.

ISSN:0003-6951    

DOI:10.1063/1.96558

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The spectral linewidth of a GaAlAs double heterostructure laser placed in a high magnetic field is measured at 190 K. It is found that the power‐dependent spectral linewidth is reduced by a factor of 0.6 in a magnetic field of 19 T. This reduction is believed to result mainly from the reduction of the linewidth enhancement factor &agr; due to a quasi‐one‐dimensional electronic system formed by the high magnetic field (i.e., by quantum wire effects).

ISSN:0003-6951    

DOI:10.1063/1.96559

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Picosecond transient grating experiments have been performed on a 5‐&mgr;m‐thick polystyrene film doped with naphthalene and on a 700‐&mgr;m‐thick pure polystyrene film at room temperature. In both cases, the observed acoustic modulation of the diffracted signal is explained by the formation of a thermal grating. No detectable acoustic attenuation is observed within the time delay of 6 ns, and the speed of sound obtained from the acoustic modulation period is in excellent agreement with that reported by an ultrasonic measurement. The coherent third order nonlinear electronic response observed at zero‐time delay is found to be shorter than 2 ps.

ISSN:0003-6951    

DOI:10.1063/1.96560

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The poly‐peri‐naphthalene (PPN) whisker is a typical graphitizing carbonaceous material. Graphitized PPN consists of linear graphite chains oriented perpendicular to the direction of the whisker axis and folded at the whisker edges. The formation of such a unique whisker structure can be explained from the original structure of the PPN whisker.

ISSN:0003-6951    

DOI:10.1063/1.96561

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Polarized micro‐Raman spectroscopy has been used to study polymer blends of poly (&egr;‐caprolactone), poly (vinyl methyl ether), and poly(styrene) for the first time. The banded pattern is attributed to the twist of the lamellae from microscopic (vibrational spectroscopic) measurements on the orientation of the lamellae. Polarized micro‐Raman spectroscopy is shown to be a powerful method for studying high order structures of polymers on the molecular level.

ISSN:0003-6951    

DOI:10.1063/1.96562

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report the first transmission electron microscopy (TEM) study of a HgTe‐CdTe superlattice. The superlattice consists of 250 layer pairs of HgTe‐CdTe on a (100) CdTe substrate and was grown at 175 °C by molecular beam epitaxy. Vertical cross‐section TEM images show a highly regular structure of the superlattice from the CdTe substrate to the free surface, indicating that interdiffusion effects at interfaces are minimal. Diffraction patterns taken from the first 30 pairs of layers of the superlattice from the CdTe buffer layer show a series of satellite spots up to the sixth order. This implies that the interfacial sharpness of this HgTe‐CdTe superlattice is comparable to those interfaces of high quality III‐V semiconductor superlattices. The HgTe‐CdTe superlattice exhibits an infrared photoluminescence peak at 357 meV, in reasonable agreement with theoretical predictions of its band gap.

ISSN:0003-6951    

DOI:10.1063/1.96563

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

In thin films (1140 A˚) of silicon doped with phosphorus, secondary or abnormal grain growth leads to bimodal grain size distributions and eventually to grains much larger than (≳25×) the film thickness. The resulting grains have nonrandom texture and are thought to be the result of surface‐energy‐driven secondary grain growth. The rate of secondary and normal grain growth increases with increasing P content. This rate increase is thought to be due to an increase in the grain boundary mobility. The rate of normal grain growth is unchanged or slightly increased when films are doped with boron. The secondary grain boundary mobility enhancement that occurs due to P doping can be compensated (reduced or eliminated) when films are co‐doped with B.

ISSN:0003-6951    

DOI:10.1063/1.96510

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Advanced compound semiconductor devices require increasingly stable, shallow, and uniform metallized layers for ohmic and Schottky contacts. However, the design of new multielemental contact metallization systems is limited by the paucity of information regarding the structure, composition, and stability of phases resulting from the interaction of single metal layers with compound semiconductors. In this letter, the results of a transmission electron microscopy investigation of the Ni/GaAs reaction are presented. The first reaction product is shown to have the composition Ni3GaAs. Based on this composition and lattice parameter measurements, it is proposed that the structure of Ni3GaAs is closely related to that of &ggr;’ Ni3Ga2, a derivative of the hexagonal B8 structure type.

ISSN:0003-6951    

DOI:10.1063/1.96511

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The surface‐limited release of deuterium from solution in polycrystalline iron was measured in ultrahigh vacuum using nuclear reaction analysis and ion implantation with surface characterization by Auger electron spectroscopy. For a bare iron surface the magnitude and temperature dependence of the release rate are quantitatively predicted by a model in which the rate limiting step is the recombination and desorption of deuterium chemisorbed on the surface. The release rate decreased approximately linearly with oxygen coverage up to a cutoff at about 0.4 monolayer.

ISSN:0003-6951    

DOI:10.1063/1.96512

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Amorphous Si:H and Si1−xGex:H films were prepared by mixing electron beam evaporated silicon with a molecular beam of germanium from a Knudsen cell and with a beam of ionized hydrogen produced by a 0–3 keV ion source. Aluminum Schottky barriers on two types of samples of (1) amorphous Si1−xGex:H with 0.15<x<0.85 and (2) modulated structures of 50×100 A˚ layers of amorphous Si:H/a‐Si0.8Ge0.2:H (10−5Torr PH hydrogen) were investigated. Barrier height was found to depend on the Ge concentration and possible Fermi level pinning due to the dangling bond deep level. The modulated structures showed a negative resistance region and a barrier height determined only by the composition of the first layer.

ISSN:0003-6951    

DOI:10.1063/1.96513

出版商:AIP    

年代:1986

数据来源: AIP