Date of Award

2006

Document Type

Thesis

Degree Name

Master of Materials Science and Engineering (MMatSE)

Department

Materials Science

First Advisor

Dr. Yousef Haik

Second Advisor

Dr. Maamar Benkraouda

Third Advisor

Dr. Hassan Ghmlouche

Abstract

Because of the high critical temperature (Tc) that the new superconductors can reach, thin films can be used in a number of technological applications. One of the major applications of thin films is in the microwave devices, where superconducting strips are used as resonators, filters, delay lines, etc. The importance of the superconductors resides in the low losses incurred during the transmission along the strip. For example, the surface resistance of a high-Tc superconductor is at least one order of magnitude less than a similar one made of ordinary conductors. Because of this advantage, there is an increase in the use of superconducting strips instead of normal conductors in a number of electronic devices.

Modeling of different behaviors of the high-Tc superconductors are still phenomenological with a number of adjusting parameters, Because of the lack of knowledge about the real mechanisms behind the pairing occurring in the high-Tc superconductors. In a type-II superconductor, loss occurs mainly because of the motion of vortex, generated by either an external magnetic field or the self-field of an applied current, due to the Lorentz force exerted by the current flowing in the superconductor. Therefore, the need to know the exact dynamics and hence the distribution of the current density in a superconductor is of primordial importance to calculate the loss incurred during Radio Frequency (RF) transmission. Because the nature of the pairing in the high-Tc superconductors is not settled yet, and the role of fluctuations due to high temperature, new phenomenological formula for different parameters, such as the penetration depth, the conductivity, etc., have to be taken into consideration, as well.

In this thesis, the FDTD method is formulated and applied to model the loss occurring during the transmission of an RF signal through superconducting micro strip. Different parameters including the surface impedance and current density distribution, as function of width and thickness, are calculated. The effect of temperature variation on these parameters is also investigated. It is found that they are temperature dependent.

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