摘要:

Organic light-emitting diodes using thin film dispersing a hole transport material into a soluble polyimide as a hole transport layer and the sublimed molecular film of a chelate complex as an emissive layer were fabricated. In order to improve the injection of electrons into the emissive layer as well as the durability of devices, we have attempted mixing the chelate complex and metal between the emissive layer and the cathodic electrode. The charge injection of the device with the mixed layer was initialized at an applied voltage of 4.19 V. It was observed from the electroluminescent spectra that the oscillator strength was dramatically enhanced with the applied voltage. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121175

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have investigated the pair tunneling process inYBa2Cu3O7−xstep-edge Josephson junctions by studying the lifetime of the metastable zero-voltage state determined by the thermal activation out of the potential well. The junctions have a hysteretic current–voltage characteristic at 4.2 K, which allows the recording of transitions and switching distribution from the Josephson current to the resistive state. By applying an external magnetic field, we have found a strong dependence of the activation energy on the field intensity. Striking similarities with analogous measurements performed on lowTcconventional tunnel junctions suggest that the highTccounterparts can be described by a standard model for long junctions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121176

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

SuperconductingYBa2Cu3O7−x(YBCO) thin films with a surface resistance of 0.86 m&OHgr; at 10 GHz and 76 K have been grown on polycrystalline ferrite yttrium iron garnet (YIG) substrates. The chemical and structural mismatches between YBCO and YIG are solved by using a double buffer layer of biaxially oriented yttria-stabilized zirconia (YSZ) andCeO2,where YSZ is deposited by an ion-beam-assisted-deposition technique. The YBCO films arecaxis oriented with an in-plane mosaic spread [full width at half maximum of an x-ray &fgr;-scan on (103) reflection] of less than 8°. The films have a superconductive transition temperature above 88 K with a transition width less than 0.3 K, giving a critical current density above106 A/cm2in self field at 75 K. At 75 K in an external magnetic field of 1 T perpendicular to the film surface, the films maintain a critical current density over2×105 A/cm2.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121177

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have studied the effects of halogenizingHgBa2CaCu2O6+&dgr;(Hg-1212) thin films and have found that the addition of chlorine/fluorine significantly enhances (1) the reproducibility and stability of Hg-1212 thin films, (2) the phase purity of Hg-1212 to over 90&percent;, and (3) the magnetic critical current density(Jc,mag)both at zero field and in-field. A possible mechanism of preventing contamination of precursor materials by chlorine/fluorine doping is proposed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121178

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We studied the proximity effect in a series ofYBa2Cu2.7Fe0.3Oy/YBa2Cu3O7−&dgr;bilayer film with varyingYBa2Cu3O7−&dgr;thickness. In a bilayer of isolated YBCO islands, aTcof 72 K was observed, much higher thanTcof 32 K of theYBa2Cu2.7Fe0.3Oyfilm.TcandJcof thicker bilayers of continuousYBa2Cu3O7−&dgr;films were found to decrease with decreasing YBCO thickness. This behavior ofTcandJccan be explained by the Deutscher de Gennes theory for the proximity effect, provided one models the film as a series of grains whose lateral dimensions scale with the average film thickness. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121179

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have observed superconductivity induced by proximity effects for 100 nm thick (001)PrBa2Cu3O7−&dgr;films pseudomorphically grown on (001)YBa2Cu3O7−&dgr;single crystal substrates by vertical four-probe measurements. The induced superconductivity disappeared around 28 K and was recovered at around 15 K. The 220 nm thick (001)PrBa2Cu3O7−&dgr;/YBa2Cu3O7−&dgr;bilayers show nonlinearI–Vbehavior with 0.2 mV built-in potential at low temperature below 50 K. The local maximum of the vertical resistance appears around 25 K. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121180

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the results of magnetization measurements on pseudomorphic (fully strained)c-axis oriented colossal magnetoresistance manganite thin films grown by molecular beam epitaxy. We observe uniaxial magnetic anisotropy (hard axis/easy plane) with the easy plane being the film plane. Within the plane a weaker biaxial anisotropy is observed with [100] (Mn–O bond direction) easy axes. The magnetization dependence of the uniaxial anisotropy constant follows the predicted magnetization dependence of the magnetostriction constants within single-ion models indicating that the anisotropy energy is dominated by strain-induced anisotropy from the lattice constant mismatch with theSrTiO3substrate. These results indicate a magnetostriction constant&lgr;100≈+7×10−5,and an induced orbital moment of at least0.02&mgr;b/Mnion. We predict that by appropriate substrate selection an equilibrium out-of-plane magnetization can be produced. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121181

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe a technique for extracting topographic information using a scanning near-field microwave microscope. By monitoring the shift of the system’s resonant frequency, we obtain quantitative topographic images of uniformly conducting metal surfaces. At a frequency of 9.572 GHz, our technique allows a height discrimination of about 55 nm at a separation of 30 &mgr;m. We present topographic images of uneven, conducting samples and compare the height response and sensitivity of the system with theoretical expectations. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121182

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Alkanethiol self-assembled monolayers (SAMs) on a mercury surface are used to build a junction consisting of two opposing mercury surfaces with interposed SAMs: Hg-SAM/SAM-Hg. The liquid mercury surface provides a support for the SAM that is smooth, compliant, free of defects, and without the incommensurate lattice properties that characterize solid metal surfaces. The thickness of the dielectric(∼30–90 Å)in this junction can be easily changed by using alkanethiols with different lengths. From capacitance measurements, a dielectric constant of2.7±0.3is calculated for the SAMs. The conductivity of SAMs on the Hg surface is&sgr;=6±2×10−15 &OHgr;−1 cm−1,a value close to that of bulk polyethylene. The junction sustains an electric field of 6 MV/cm. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121183

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Electrical properties of the interface betweenBi4Ti3O12ferroelectric film andp-Si substrate have been studied by capacitance–voltage(C–V)characteristics. It is found that the interface barrier can be broken down temporally because of the charge injection from Si substrate into the ferroelectric thin film, and this charge injection behavior induces hump and valley structures in theC–Vcurves. It is also found that the polarization in theBi4Ti3O12film is aligned along a preferential direction from semiconductor to ferroelectric thin film, which is attributed to the ferroelectric/p-Si contact. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121184

出版商:AIP    

年代:1998

数据来源: AIP