Graduation Year

2005

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Ashok Kumar, Ph.D.

Co-Major Professor

Shekhar Bhansali, Ph.D.

Committee Member

Thomas Weller, Ph.D.

Keywords

Bst, Rf, Tunability, Pld, Sputtering

Abstract

The dependence of dielectric permittivity on the applied electric field, high dielectric constant and low cost makes barium strontium titanate (BST) a promising ferroelectric material for applications in tunable microwave devices. High tunability and low dielectric loss is desired for tunable microwave devices. The primary objective of this research was to optimize the tunability and dielectric loss of BST thin films at microwave frequencies with different deposition techniques. Ba0.5Sr0.5TiO3 thin films were grown on Pt/TiO2/SiO2/Si, by pulsed laser deposition (PLD) and sputtering. Parallel plate capacitor structures were designed using ADS and fabricated. The microstructural and phase analysis of the BST films were performed using X-ray diffraction (XRD) method. The diffraction patterns are attributed to cubic (perovskite) crystal system. The analysis of surface morphology was done using atomic force microscopy. Electrical properties of parallel plate capacitors were measured using LCR meter and tunability of 2.4:1 and loss tangent of 0.05 was achieved at low frequencies for laser deposited BST thin films. Tunability of 2.8:1 and loss tangent of 0.03 was achieved at low frequencies for sputtered BST thin films. The correlation of optimized structural and dielectric properties of thin films deposited by pulsed laser deposition and sputtering technique was analyzed and compared. The structural characterization of sputtered BST thin film on MgO, Alumina and LaAl2O3 was achieved for the fabrication of interdigital capacitors. Interdigital capacitor has been designed using ADS momentum.

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