Graded ferroelectric capacitors with robust temperature characteristics

El-Naggar, Mohamed Y.; Dayal, Kaushik; Goodwin, David G.; Bhattacharya, Kaushik
December 2006
Journal of Applied Physics;12/1/2006, Vol. 100 Issue 11, p114115
Academic Journal
Ferroelectric thin films offer the possibility of engineering the dielectric response for tunable components in frequency-agile rf and microwave devices. However, this approach often leads to an undesired temperature sensitivity. Compositionally graded ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. In this paper, we present a continuum model to calculate the capacitive response of graded ferroelectric films with realistic electrode geometries by accurately accounting for the polarization distribution and long-range electrostatic interactions. We show that graded c-axis poled BaxSr1-xTiO3 (BST) parallel plate capacitors are ineffective while graded a-axis poled BST coplanar capacitors with interdigitated electrodes are extremely effective in obtaining high and temperature-stable dielectric properties.


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