摘要:

We report on the influence of60Co gamma‐radiation upon the properties of Cr‐GaAs diode structures. Auger depth profiling proved that while a low dose of radiation made the transition region wider, higher doses caused its narrowing. Radiation treatment affected the Schottky barrier height and ideality factor favourably. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114495

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence spectroscopy has been used to investigate the behavior of Hg, implanted into MBE‐grown GaAs. A new recombination path in the near‐band‐edge region at 1.51291eV is identified with the neutral Hg‐bound exciton recombination (Hg°X), with a localization energy following an anti‐Haynes’ rule. The electron‐acceptor and donor‐acceptor transitions are displayed at 1.466 and 1.463 eV, respectively. From the temperature dependence of the photoluminescence, the value of 52.5 meV is extracted for the binding energy of the Hg acceptor in GaAs. With the resonant excitation of the Hg°Xline, the electronic signature of the Hg acceptor in GaAs is further evidenced, with the observation of two‐hole transitions. Transitions to 2sas well as 3sstates are resolved, with Raman shifts of 37.2 and 44.8 meV, respectively. The corresponding binding energies are thus 15.3 and 7.7 meV, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114496

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Visible light emission from porous silicon can be stimulated by applying a positive bias to a formic acid/sodium formate liquid junction cell. The emission lasts for 45 min at +2.75 V applied potential (<5 mA/cm2, power conversion efficiency ≳10−2%) and is reliably generated fromn‐ orp‐type porous silicon. An applied voltage as low as 1.3 V is capable of generating the red (720 nm) emission, indicating that current‐induced chemical reactions aid in the generation of charge carriers. A mechanism involving oxidation of formic acid followed by electron injection from a CO2−radical is proposed. Infrared spectra of the porous silicon surface taken after anodization show formation of a stable silyl‐ester species that is thought to be responsible for the increase in radiative recombination efficiency through passivation of surface defects. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114497

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using various size rectangular mesas formed by photolithographically patterning and etching on single‐crystal Bi2Sr2Ca1Cu2Oxsuperconductors, we have obtainedc‐axis volt‐ampere characteristics as a function of magnetic field applied parallel to thea‐bplanes. Enhanced sensitivity with field perpendicular to the long side was observed even in mesas with dimensions smaller than the magnetic penetration depth &lgr;c. This can be explained in terms of viscous flow of Josephson vortices. The measurements are in good quantitative agreement with theoretical models for Josephson vortex motion in layered superconductors. Vortex flow coexists with the multiple hysteretic structure previously presented as evidence that this material behaves as a stack of underdamped intrinsic Josephson junctions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114498

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The low‐frequency noise in multiloop dc superconducting quantum interference device (SQUID) magnetometers fabricated from low‐Tc(transition temperature) materials was investigated. The magnetometers are operated in a flux‐locked loop based on additional positive feedback (APF). A simple noise reduction scheme for dc SQUIDs with APF is presented that eliminates the influence of critical current and resistance fluctuations without deteriorating the white noise performance. Applying this scheme to a magnetometer with a low‐frequency two‐level switching due to a single trap in the SixNytunnel barrier reduced the switching amplitude of &bartil;10−3&Fgr;0by at least two orders of magnitude down to a level below the intrinsic magnetometer flux noise. Using simple direct‐coupled readout electronics with a 10 kHz bias reversal, a high bandwidth of &bartil;1 MHz, a low white flux noise of 1.5×10−6&Fgr;0/&sqrt;Hz, and a 1/fnoise corner frequency of 4 Hz have been measured. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114499

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of electric field on ultrathin YBa2Cu3O7−&dgr;grain boundary Josephson junctions has been investigated. A conventional metal insulator superconductor field effect transistor structure consisting of aPr0.55Y0.45Ba2Cu3O7−&dgr; /YBa2Cu3O7−&dgr;bilayer channel, a crystalline SrTiO3dielectric, and an Au gate electrode is deposited on a SrTiO3bicrystal substrate. At high bias current (Ibias≫Ic) the observed effect is compatible with a parallel resistor model using a value close to the bulk charge carrier density of YBa2Cu3O7−&dgr;. At low bias current (Ibias≥Ic) an enhanced field effect not compatible with a parallel resistor model is observed. This enhanced effect is related to the field dependent dielectric properties of the crystalline SrTiO3insulation layer. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114500

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Complex magnetic structures were observed on a durability tested TbFeCo magneto‐optical disk. By considering the magnetic properties of the TbFeCo and the polarized microscopic image of the same region, it was concluded that those complex structures result from the decrement of the compensation temperature of the TbFeCo film at the track center. Samples that were exposed to static magnetic fields were also observed for the purpose of inspecting the changes in the coercive force of the damaged regions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114501

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report here on an experiment in which picosecond electron pulses, produced by a compact radiation frequency (rf) electron gun, were used to excite a rectangular waveguide, generating 5 ps pulses of radiation with a bandwidth of ∼200 GHz. The interaction of the electron pulses with the waveguide can be modeled quite simply by performing a harmonic expansion of the pulse train produced by the electron gun and employing Poynting’s theorem to compute the power coupled into the modes of the waveguide by each harmonic. The resulting model for the distribution of spectral power yields good agreement with the observed spectrum. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114502

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Surface diffusion coefficients,DS, of platinum adatoms were measuredinsituon polycrystalline platinum electrodes inmersed in 1 M HClO4, 1 M H3PO4and 0.5 M H2SO4electrolytic solutions at different potential values. The change in theDSvalues observed, as well as the rate of change ofDSwith the potential value, confirm an adsorbate induced relaxation of Pt electrode surfaces. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114503

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Large arrays of Au nanowires down to 50 nm in width are fabricated on V‐grooved InP substrates. Holographic laser interference exposure of photoresist and anisotropic etching are used to pattern the surface of InP(001) substrates into V‐shaped grooves with a 200 nm period. Next, the patterned substrates are covered with a thin Au film, which is subsequently structured into nanowires using a well controlled wet etching process. Initial characterization confirms that the wires are electrically continuous. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114504

出版商:AIP    

年代:1995

数据来源: AIP