Ac susceptibility is used to measure a small shift of the coupling peak of the imaginary part of the ac susceptibility ([chi][double prime]) to a higher temperature as the frequency is increased. Applying the Bean model one obtains the zero-field and zero-temperature intergranular pinning potential U(0,0) and the critical, intergranular current density J[sub c](0,0) from the data. Here it is shown how one can calculate the intergranular flux creep activation energy E[sub a](T,H) as a function of the applied magnetic field H and the temperature T if the average grain radius R[sub g] and the zero temperature London penetration depth [lambda][sub L](0) are known. We arrive at E[sub a](T,H) values between 0 and about 109 meV for a range of ac fields between 0 and 20 Oe at 77 K for a sintered YBaCuO pellet. 21 refs., 1 fig.
The mobility edge concept, as it is currently being applied to understand transport phenomena in disordered semiconductors, loses a lot of the underlying physics. Arguments are presented that (dark and photo) transport can be described with a concept of an [open quotes]effective transport level[close quotes] or activated mobilities. It is argued that phenomena associated with [open quotes]transport[close quotes] can be more important than recombination in determining device performance. 27 refs., 2 figs.
It is argued that the Shockley-Read-Hall recombination model often used to describe the behavior of semiconductor devices provides only an insufficient description of the device performance and may not account for the most important mechanism that is limiting the performance of disordered semiconductor materials. Arguments are presented that in disordered materials, diffusion lengths are often limited by the effective band mobilities, which are lower than in [open quote]perfect[close quotes] crystalline materials because of long-range fluctuations of the band edges.
Nb-substituted samples of the stoichiometric composition YBa 2 (Cu 1−x Nb x ) 3 O 7−δ with 0 ≤ x ≤ 0.04 prepared under identical conditions have been characterized by a.c. susceptibility & d.c. magnetization measurements. No significant change in T c of the Nb-doped 1-2-3 compounds has been observed in spite of Nb existing in 5 state. Detailed magnetization measurements on randomly oriented powdered samples as a function of temperature and field exhibit no flux-pinning. A critical current density, J c ≃ 10 2 A.cm 2 is deduced from M(H) data at T = 10 K in a 1.0 KOe field for x = 0.01, 0.02 and 0.03 samples, which is nearly 1000 times lower than the J c of the pristine 1-2-3 powdered sample
In this work we focus on the chemical and thermal resistance of diamondlike carbon (DLC) thin films under conditions commonly encountered by an integrated circuit hermetic seal. We will show that DLC films are effectively impervious to HCl, H 2 SO 4 , and HF acid. Furthermore, DLC can withstand prolonged exposure to 200 C and thermal cycling to 225 C without loss of adhesion or chemical resistance
Artificial structures of Bi 2 Sr 2 CaCu 2 O y (superconducting BSCCO)/ Bi 2 Sr 2 CuO x (normal conducting BSCO) multi-layered thin films by multitarget RF magnetron sputterings has been characterized by X-ray diffraction (XRD), secondary-ion mass spectroscopy (SIMS) and crosssectional transmission electron microscopy (TEM). By the crosssectional TEM and XRD, it was confirmed that the BSCCO/BSCO multilayers have the c-axis normal to the substrate surface. And that the compositional modulation of the BSCCO/BSCO multi-layer film was constructed as we designed
The progress towards utilizing silver-clad bismuth cuprate high temperature superconductors in transmission cables is reviewed. By example, it specifically addresses issues in the development of a high temperature superconducting power cable at BICC Cables Ltd in the UK, one of the world's leading supertension cable manufacturers. 21 refs., 2 figs.
The effect of Cr substitution in the YBa[sub 2](Cu[sub 1[minus]x]Cr[sub x])[sub 3]O[sub 7[minus][delta]] (x = 0.01) system has been investigated. The resistance-temperature curves showed metallic behavior for samples with x [le] 0.02 and semiconductor-like behavior for x [ge] 0.03. The resistance-temperature curves also showed very little change in the onset temperature (T[sub c] onset [approximately] 93 K) for all samples but a pronounced broadening of the superconducting-transition-width with increasing Cr content. The superconducting and normal state properties are discussed using the electrical resistivity, X-ray diffraction, Energy Dispersive X-Ray Analysis (EDAX), and Scanning Electron Microscope (SEM) observations. 16 refs., 5 figs., 1 tab.
Artificial structures of Bi[sub 2]Sr[sub 2]CaCu[sub 2]0[sub y](superconducting BSCCO)/ Bi[sub 2]Sr[sub 2]CuO[sub x] (normal conducting BSCO) multi-layered thin films by multitarget RF magnetron sputterings has been characterized by X-ray diffraction (XRD), secondary-ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy (TEM). By the cross-sectional TEM and XRD, it was confirmed that the BSCCO/BSCO multilayers have the c-axis normal to the substrate surface. And that the compositional modulation of the BSCCO/BSCO multi-layer film was constructed as we designed.
Recently it was shown that reaction at the interface at room temperature between a bifluoride and a vanadate in solid state across the ever growing reaction product layer takes place by continuous transport of the bifluoride along with its associated cation into the vanadate side. In this paper, scanning electron microscopic evidence is presented to show that the transport of the bifluoride into the vanadate side of the product interface does take place. The possible role of moisture as well as the structure of the product in this kind of solid state reactions is discussed.
A mathematical description of photoelastic polarization modulators is developed for the general case in which the modulator exhibits a static retardation that is not colinear with the dynamic retardation of the modulator. Simplifying approximations are introduced which are appropriate to practical use of the modulators in polarization measurements. Measurement errors due to the modulator static retardation along with procedures for their elimination are described for reflection ellipsometers, linear dichrometers, and polarimeters.
In order to test a simplified approach to evaluate the carrier induced refractive index change in III-V semiconductors, the optically induced changes in refractive index have been measured in an AlGaAs waveguide structure in a wavelength range varying between 875 and 900 nm using a Mach-Zehnder interferometer set-up. The experimental results have been compared with the above-mentioned theoretical model and a quite good agreement has been found.
The authors report successful fabrication of superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} wire, where yttrium metal wire was used as a precursor and core. The surface of the wire was first oxidized, and was then coated by molten Ba-Cu-O. After annealing in oxygen, a superconducting layer was formed between the yttrium core and the Ba-Cu-O. The results demonstrated the feasibility of producing superconducting wire of arbitrary length with a naturally occurring thermal, chemical, and electrical insulating layer.
