摘要:

The absorption characteristics of GexSi1−xquantum well infrared photodetector (QWIP) structures have been studied in samples over a range of germanium compositions and doping levels. In all these samples, quantum well intersubband transitions are either very weak or nonexistent for normally incident light. However, free carrier absorption in GexSi1−xquantum wells is a strong absorbing mechanism in the long wavelength infrared regime, and has been found to be stronger than in silicon for similar doping levels. Therefore, detectors relying upon free carrier absorption in GexSi1−xquantum wells may offer superior responsivity and quantum efficiency. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114454

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on optical and vibrational properties of porous silicon (por‐Si) layers grown onp‐type Si wafers by electroless etching technique. The results indicate a correlation between the photoluminescence (PL) intensity and the multihydride complexes (SiHnwithn≥2). However, similar correlation was also found for monohydride species from the layers containing no multihydrides. It is shown that the increase in the amount of oxidation is responsible for broadening of the PL emission band. Furthermore, a new IR absorption band is observed at 710 cm−1and assigned to multihydrides suggesting a new local bonding environment for hydrogen atoms in these layers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114429

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The structure of high angle boundaries in the (BiPb)2Sr2Ca2Cu3Oxsystem, which is compositional and structurally modulated along the boundaries, was investigated by high resolution electron microscopy. These compositional variable boundaries tend to facet onto the (001) plane, leaving steps of height equalc/2 for the (BiPb)2Sr2CuOxand (BiPb)2Sr2Ca1Cu2Oxphases with amorphous material at the corners of these steps. These data suggest a weak link is formed at high angle boundaries where there are such lowerTcor insulating phases. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114430

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This letter describes a method to sense slight off‐stoichiometry (less than 2%–3%) in the cation ratio [Cu/(Pr+Ce) or Cu/(La+Sr)] of atomic beam fluxes by detecting precipitated impurity phases on the surface using reflection high‐energy electron diffraction during growth ofT′‐(Pr,Ce)2CuO4andT‐(La,Sr)2CuO4films. The method is based on the facts that off‐stoichiometry of fluxes inevitably produces precipitates of certain impurity phases on the surface in film growth of these oxides, and that the species of the impurity phases are solely determined by the type of off‐stoichiometry; copper rich or lanthanoid rich. Furthermore, it has been found that it is possible to recover a precipitate‐free surface, from a surface with precipitates produced by lanthanoid‐rich deposition, by later flux readjustment, but it is difficult from a surface with precipitates produced by copper‐rich deposition. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114431

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new design for high‐energy radiation/particle detectors is presented. The nonequilibrium response of a superconductor to the absorption of the incident quanta is sensed by electromagnetic measurements of the altered dynamic conductivity. Microwave absorption may be used to amplify the signal. Such a detector will provide better energy resolution than semiconducting charge‐collection devices once the statistical resolution limit is reached. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114432

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Recent microstructural studies of high‐Jc, Tl‐1223, spray‐pyrolyzed thick films have shown that the high‐Jcand reduced weak‐link behavior can be ascribed to the presence of a unique microstructure, wherein the film is divided into ‘‘colonies’’ of biaxially aligned regions. In an effort to understand the nucleation and growth of Tl‐1223 as well as the formation of the colony microstructure, several sets of films quenched from various stages of the high‐temperature thallination process were examined using electron microscopy, x‐ray diffraction and electron backscatter diffraction (EBSD). It is found that the crystallization of the 1223 phase is associated with formation of a liquid phase which contains significant amounts of all oxides. Furthermore, it is found that the film nucleates at the substrate on the side closest to the thallium source. The growth front then moves up through the thickness and along the length of the film. X‐ray microdiffraction measurements show that local biaxial alignment or the formation of colonies starts to occur at the onset of 1223 crystallization. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114433

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The magnetic microstructure in a Co/Pt multilayer has been imaged by magnetic force microscopy employing a novel tip structure. Magnetic tips have been fabricated by evaporating a thin film onto a single facet of the pyramidal tip of a silicon nitride cantilever. Nanolithographically defined elements have been used to simulate the micromagnetic structure of the tip and have been investigated by the Lorentz mode of electron microscopy. We demonstrate that stray fields from the Co/Pt multilayer can be sensed by the tip producing images of the magnetic microstructure with a fine structure on a scale of 30–40 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114434

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Ground‐state CF and CF2radicals in CF4helicon plasmas of high density were detected by laser‐induced fluorescence (LIF). The LIF was used to measure the spatial and temporal variations of CFxconcentrations. The CF2concentration increases near 5–10 ms after the extinction of rf power, and the degree of this increase depends upon the discharge condition; plasma duration, plasma density, and CF4pressure. The result indicates that this behavior in the afterglow is closely related to the interactions of the rf‐on phase between radicals and a quartz surface with deposited fluorocarbon polymers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114435

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.115555

出版商:AIP    

年代:1995

数据来源: AIP