摘要:

A possibility to control a thin superconducting channel through the proximity effect is analyzed on the basis of simple one‐dimensional solutions of the equation for the order parameter in the dirty limit. By estimating the transconductance, the feasibility of the three‐terminal device based on such a mechanism is discussed.

ISSN:0003-6951    

DOI:10.1063/1.105627

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Time‐resolved optical absorption spectroscopy techniques were used to study Ba, metastable Ba+, and YOabsorptionsin the laser‐produced plasma plume from a YBa2Cu3O7target. Results obtained indicate an initial explosive removal of material from the target surface followed by a subsequent evaporation process. Some YO is ejected from the target in molecular form, particularly at laser fluence <6 J/cm2, whilst additional YO is formed in subsequent reactions of Y with oxygen at the plasma plume edges. The formation of metastable Ba+(52D5/2) is also observed in the outer reactive layers of the plasma plume.

ISSN:0003-6951    

DOI:10.1063/1.105628

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Preparation and characterization of dc SQUIDs based on YBa2Cu3O7/Ag/YBa2Cu3O7edge junctions is reported. The SQUIDs were preparedinsituby a multistepalllaser ablation deposition process. Since the Ag on YBa2Cu3O7was exposed to 730 °C in O2ambient, the barrier resistance was quite high, ∼0.6 &OHgr;. The SQUIDs showed voltage periodicity versus magnetic fieldH⊥up to ∼80 K and had a maximum response of 30 &mgr;V/&Fgr;0at ∼70 K, whereIcRNwas 30 &mgr;V. The SQUID response versusH⊥was superimposed on a diffractionlike pattern of its junctions, indicating an improved uniformity in the junction cross section. When the SQUID was exposed to microwave radiation, many pronounced Shapiro steps were observed in theI‐Vcurve, which modulated with the microwave power.

ISSN:0003-6951    

DOI:10.1063/1.105603

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The atomic structure of (001) surfaces ofc‐axis‐oriented YBa2Cu3O7−x(YBCO) thin films was studied by low‐energy ion scattering spectroscopy (ISS) after annealing in ultrahigh vacuum. This is the first report on the surface analysis of superconducting oxide evaluated by ISS. A clean surface of YBCO (001) 1×1 is produced by annealing at around 500 °C. The surface structure is discussed in terms of the blocking and the nonblocking effects caused by the desorption of O(4) atoms. We conclude that the (001) surfaces are stabilized by Cu(1)‐O chains.

ISSN:0003-6951    

DOI:10.1063/1.105604

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

High‐temperature x‐ray studies of the melting of Bi2Sr2Ca1Cu2O8−&dgr;/Ag composites have been undertaken in order to determine the factors that control the melting temperature and the various phases that form during the melt‐processing part of the fabrication of these conductors. During the melting process, three distinct phases form and then dissolve in the Bi‐rich liquid: first (Sr,Ca)1Cu1O2, then (Sr,Ca)2Cu1O3, and finally (Sr,Ca)O. Ag suppresses the melting point about 30 °C and as much as 10% Ag can dissolve in the Bi‐rich liquid. A slight Bi excess also decreases the temperature where the Bi2Sr2Ca1Cu2O8−&dgr;structure disappears and liquid forms.

ISSN:0003-6951    

DOI:10.1063/1.105605

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The change in superconducting properties due to the presence of a bias electrode ininsitulaser deposition was explored. It was found that the bias ring allowed a 50–70 °C reduction in the deposition temperature. This reduction is correlated to an increase in ion current impinging on the substrate.

ISSN:0003-6951    

DOI:10.1063/1.105606

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An improvement in zero resistance temperature (T0c) of the 2223 phase in the Bi‐Sr‐Ca‐Cu‐O system by using a nominal composition Bi0.8Pb0.2SrCa2Cu2Oxhas been achieved. The bulk Bi0.8Pb0.2SrCaCu2Oxsamples synthesized from a matrix reaction method exhibited a superconducting transition withT0cof 110 K. Addition of one Ca‐atom per molecule of the above composition, that is, Bi0.8Pb0.2SrCa2Cu2Oxresulted in enhancedT0cof 122 K with onset temperature (Tonsetc) of 140 K. Interestingly,T0cof 122 K was also observed in the Pb‐free BiSrCa2Cu2Oxsamples, but it decreases to 115.5 K after 3–4 thermal cycles. However, no such decrease inT0cwas observed in the Pb‐doped samples, indicating the formation of stable 2223 phase. On the basis of x‐ray diffraction, energy dispersive spectra and scanning electron microscopy data, it is concluded that excess of Ca facilitate the nucleation of 2223 phase.

ISSN:0003-6951    

DOI:10.1063/1.105607

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Ni/Pt multilayers have been prepared by electron beam evaporation under ultrahigh vacuum conditions. All the samples were grown at 300 K. Thet(Ni) was in the range 0.7–2.1 nm andt(Pt) was fixed at 2 nm. The magnetization and the Curie temperature for these samples are lower than that of bulk Ni. For the samples witht(Ni)≤1 nm perfect rectangular hysteresis loops are obtained along the film normal in the low temperature range (5 to 70 K) indicating the presence of a strong uniaxial anisotropy. The coercivity for the sample witht(Ni)=0.7 nm at 5 K is as high as 4.7 kOe.

ISSN:0003-6951    

DOI:10.1063/1.105608

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A study is presented on the assessment of the Fe2+concentration in Fe‐doped InP by the quantitative evaluation of the Fe2+intracenter absorption at 2800–3200 cm−1. Based on a comparison with secondary‐ion mass spectrometry data fromn‐type samples, a calibration factor is derived for the oscillator strength of the zero‐phonon lines at 10 K. The detection limit for 500 &mgr;m samples is ≊5×1013cm−3.

ISSN:0003-6951    

DOI:10.1063/1.105609

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A field‐effect transistor in which the ferroelectric lithium niobate (LiNbO3) replaces the oxide in a conventional metal‐oxide‐semiconductor transistor has been fabricated. The channel conductance of this device has been shown to be strongly affected by the application of voltage pulses between the gate of the device and the substrate. A reduction of channel current of nearly 140 &mgr;A was observed after the application of a voltage pulse of −30 V and partially restored witha+10‐V pulse. This behavior was found to be consistent with the influence of the polarization charge of the LiNbO3layer on the carriers in the channel. This is the first observation of such behavior in a metal‐ferroelectric‐semiconductor field‐effect transistor without the growth of a buffer layer between the semiconductor and ferroelectric to prevent charge injection.

ISSN:0003-6951    

DOI:10.1063/1.105610

出版商:AIP    

年代:1991

数据来源: AIP