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Research is presented concerning the investigation of the relationships which exist between the dielectric and microstructure properties of epitaxial films of ferroelectric barium titanate.

Research was conducted to examine the low frequency current noise in single electron transistors (SET) as a function of gain. it was found that the noise follows the gain in such a manner that the noise of the SET is dominated by input noise for almost all values of bias and gate voltage for the Al SET. However, it was found that there was a contribution from other sources when the gain is low for the Nb SET.

High-current-density Josephson junctions and high-transition-temperature superconducting YBaCu3O7-delta (YBCO) are grown on silicon on sapphire epitaxially by a new method. The method uses CeO2/YS2 as a buffer layer, which eliminates the possibility of Si substrates reacting with YBCO during deposition. The seed layer is a thin MgO layer, which facilitates the formation of YBCO layer with different crystal orientations. This results in the formation of a biepitaxial crystallographic grain boundary that is sensitive to growth conditions.

Experimental and simulation studies help evaluate a designed, high-Tc super conductor-based direct current to a single flux quantum converter loaded with a Josephson transmission line and coupled through a slot antenna to a millimeter wave external generator. Results of the experimental study agree with the simulation results, thus indicating the digital operation of the device. These converters help develop fast Josephson samples that can be used to test high-Tc rapid single flux quantum circuits.

Deposition of YBa2Cu3O7 thin films on SrTiO3 and Y-ZrO2 bicrystal substrates generates superconducting quantum interference devices (SQUID) and Josephson junctions. Current-voltage characteristics of the junctions are similar to resistivity-shunted junctions model. A temperature-dependent voltage modulation depth and Fraunhofer-like response of critical current to magnetic fields are observed.

Laser deposition methods yield YBa2Cu3O(7-X)/insulator/YBa2Cu3O(7-x) trilayers having one PrGaO3 layer and an SrTiO3 (STO)/PGO multilayer. Pinholes in PGO layers produce superconducting microshorts, and are eliminated by introducing thin STO films as buffer layers in the PGO.

A method for designing input circuits for multiloop superconducting quantum interference devices (SQUIDS) is presented. Numerical formulae derived for multitransformer SQUID circuits were effectively used in the design. Superior energy resolution and magnetic-field gradient sensitivity were obtained. Design techniques for SQUID magnetometers could be improved accordingly.

Y1Ba2Cu3Ox (YBCO) and Y-ZrO2 (YSZ) films were grown by pulsed layer deposition technique on sapphire substrates. It was observed that the c-axis oriented YBCO grows on amorphous YSZ at an optimal thickness of YSZ. An buffer layer of nine nanometers produced a Tc of 89 Kelvin which reflect the strong correlation of the properties of YBCO and the thickness of the buffer layer. The experiment further developed a model which showed the film growth process.

Ba(sub 0.25)Sr(sub 0.75)TiO(sub 3)/SrRuO(sub 3) (BSTO/SRO) thin-film varactors were manufactured on (001)LaAlO(sub 3) substrates and characterized at rf and microwave frequencies. X-ray analysis shows epitaxial growth of (001)-oriented BSTO films with extended out-of-plane lattice parameter b=3.925 angstrom.

The temperature and electric field response of the complex dielectric permittivity and the relaxation of domain walls in a ferroelectric layer that is of sufficient quality to show a Curie-Weiss behavior is described. The relaxation rate of the ferroelectric domain walls exponentially depend on temperature an the electric field strength.

Superconducting Josephson junctions with high characteristic voltage (I(Sub c)R(Sub n) larger than 4 mV at 4.2 K) were fabricated by depositing YBa2Cu3O7-x on tilted sapphire bicrystal substrates, where the tilting axis is along the grain boundary. The findings show that a high characteristic frequency of about 2 Thz and low microwave losses in sapphire make tilted junctions promising candidates for terahertz applications such as direct Josephson detector, a Josephson oscillator, or a Hilbert spectrometer.

We report on the observation in current-voltage characteristics of YBa[sub 2]Cu[sub 3]O[sub 7-δ] (YBCO) step-edge Josephson junctions of resistive branches generated by a current injected close to the grain-boundary region through two symmetrical Au/YBCO contacts. The current amplitude and voltage tunability of the branches is measured as a function of injected current and sample temperature and the observed effects are explained in terms of flux-flow dynamics in long Josephson junctions. As the voltage of the branches can be tuned up to 2.5 mV, the investigated phenomenon is also appealing for practical applications in the submillimeter-wave range of the electromagnetic spectrum. We estimate the available power and the linewidth of the electromagnetic radiation associated with typical bias points. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]