摘要:

High‐temperature‐superconductor Josephson junctions with an edge geometry of superconductor/normal‐metal/superconductor have been fabricated on yttria‐stabilized zirconia substrates by engineering the electrode andN‐layer material to reduce the lattice mismatches (a,b, andc). With GdBa2Cu3O7−&dgr;as electrodes and Pr‐doped Y0.6Pr0.4Ba2Cu3O7−&dgr;as a barrier, the lattice mismatches from electrode and barrier layer are reduced to a very low level. The junctions fabricated with such a design demonstrate resistively shunted junction current‐voltage characteristics under dc bias at temperatures in the range of 77–88 K. The quite low specific interface resistivity on the order of 10−10&OHgr; cm2indicates that the junction performance is controlled by the normal‐metal (N) layer material instead of the interfaces. The use of lattice‐matched electrode and N‐layer material is one of the key design rules to obtain controllable high‐temperature superconductor Josephson junctions. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360094

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An intense electron beam travelling axially through a superconducting tube is studied. We show numerically that it is necessary to compensate the space‐charge effect of the electron beam nearly completely in order to focus the beam by means of the superconductor tube. The tube functions as a lens not only for electrons injected parallel to the tube axis but also for electrons having a small initial radial velocity component. Additionally, it is suggested that the simple straight superconducting tube may function as a wiggler for free‐electron lasers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360095

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Aluminum and nickel contact metallizations have been investigated on polycrystalline, randomly oriented diamond films of varying dopant concentrations. Hall measurements have been used to characterize the diamond films to indicate good control of dopant incorporation with carrier mobility comparable with those of the highest reported in similar films. Rectifying characteristics have been observed for both Al and Ni contacts provided the sheet resistance of the films is greater than 1200 &OHgr;/sq. The thermal stability of these contacts have been investigated to 400 °C and Al diodes have been found to be electrically stable to such treatments. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360096

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrical properties of BC2N thin films have been investigated in terms of the temperature dependence of the resistivity and Hall effect measurements. The BC2N thin films were prepared by chemical vapor deposition from acetonitrile and boron trichloride on polycrystalline Ni and quartz substrates. The experimental results indicated that the BC2N films werep‐type semiconductors on both substrates, with acceptor levels between 7.5 and 23 meV relative to the valence band. The hole mobility on Ni substrates was one order of magnitude higher than that on the quartz substrates, suggesting that the thin film quality is better on Ni substrates than on quartz substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360029

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In highly doped thin semiconductor layers one often observes generation‐recombination (g‐r) noise with a broadened Lorentzian‐like spectrum. In a theoretical analysis we have shown that such a spectrum can be ascribed tog‐rprocesses between conduction band and monoenergetic traps in the edge of the layers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360030

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence and Raman spectroscopies are employed to study undoped InGaP layers grown on GaAs (100) substrates at 750 °C by liquid phase epitaxy. There are four peaks in the photoluminescence spectrum in the energy range between 1.55 and 2.25 eV. Besides a bound exciton recombination, three longitudinal optical phonon replicas with one superimposed donor‐acceptor emission are identified based upon their dependences of emission energies on temperature and excitation intensity. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360031

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report a study of the interfaces of InGaAs/InGaAsP quantum wells (QWs) grown by gas‐source molecular beam epitaxy. By optimizing the group‐V source supply sequence, a photoluminescence (PL) linewidth as narrow as 6.6 meV has been observed from a 2 nm wide single QW. The PL linewidths have been analyzed to evaluate the contributions of alloy compositional scattering and interface roughness. The analysis shows that for QW structures grown with the optimized growth sequence, the PL linewidth is mainly due to alloy compositional variations, whereas the contribution from interface roughness is small, indicating a good interface control. By considering the strain effect on the band alignment of the InGaAs/InGaAsP heterojunction, theoretical transition energies of QWs have been calculated using the envelope‐function approximation, and the results agree well with the experimental data. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360032

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Defects just beneath the mirror surface of a silicon wafer grown by the Czochralski method is critical for epitaxial growth on the surface. Inside total reflection of an IR laser beam allowed only the light scattered by defects and tiny inclusions in the denuded zone of the wafer to be observed through the surface, because part of the scattered light makes an incident angle smaller than the critical one while the unscattered part of the beam is totally reflected and thus does not emerge from the wafer. Background brightness was caused by light scattering from tiny inclusions such as interstitial oxygen atoms in the zone, and inhomogeneity of this background indicated distribution fluctuation of the defects with gettering function. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360033

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Films with angular and spectral selectivity of the optical transmittance were produced by reactive magnetron sputtering with oblique incidence of the deposition species towards a substrate. These data could be reconciled with multiparameter fits to a model based on the Maxwell Garnett effective medium theory applied to a three‐component structure with inclined columns, surrounded by voids, comprised of elongated Al particles in an Al2O3matrix. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360034

出版商:AIP    

年代:1995

数据来源: AIP