Stress Driven Rearrangement Instability of Crystalline Films with Electromechanical Interaction
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0924-Z07-04
Stress Driven Rearrangement Instability of Crystalline Films with Electromechanical Interaction Peter Chung1, John Clayton2, Melanie M Cole3, Michael Grinfeld4, Pavel Grinfeld5, and William Nothwang1 1 AMSRD-ARL-CI-HC, US Army Research Laboratory, Aberdeen Proving Ground, MD, 21005-5069 2 AMSRD-ARL-WM-TD, US Army Research Laboratory, Aberdeen Proving Ground, MD, 21005-5069 3 AMSRD-ARL-WM-MA, US Army Research Laboratory, Aberdeen Proving Ground, MD, 21005-5069 4 AMSRD-ARL-WM-TD, US Army Research Laboratory, 4600 Deer Creek Loop, Aberdeen Proving Ground, MD, 21005-5069 5 Mathematics Department, Drexel University, Philadelphia, PA, 19104
Abstract It was demonstrated, on general thermodynamic grounds, that, in non-hydrostatically stressed elastic systems, phase and grain interfaces undergo morphological destabilization due to different mechanisms of "mass rearrangement". Destabilization of free surfaces due to the combined action of mass rearrangement in the presence of electrostatic field has been well known since the end of the 19th century. Currently, morphological instabilities of thin solid films with electro-mechanical interactions have found various applications in physics and engineering. In this paper, we investigate the combined effects of the stress driven rearrangement instabilities and the destabilization due to the electro-mechanical interactions. The paper presents relevant results of theoretical studies for ferroelectric thin films. Theoretical analysis involves highly nonlinear equations allowing analytical methods only for the initial stage of unstable growth. At present, we are unable to explore analytically the most important, deeply nonlinear regimes of growth. To avoid this difficulty, we developed numerical tools facilitating the process of solving and interpreting the results by means of visualization of developing morphologies. Introduction Recently, strong interest has focused on the development of tunable dielectric materials for frequency agile RF and microwave device applications [1]–[3]. Such electronic components include tunable filters, voltage controlled oscillators, varactors, parametric amplifiers, delay lines, and phase shifters [1]–[4]. Thin film Ba1-xSrxTiO3 (BST) has come to be considered one of the forerunner material systems for the realization of such tunable components. In particular, it is the composition dependent Curie temperature (TC) and the nonlinear, field dependent, dielectric permittivity of Ba1-xSrxTiO3 that makes it attractive for tunable devices at microwave frequency. In other words, BST is a material whose composition can be tuned such that under operating ambient, a nonhysteretic dielectric tunability can be produced through dc bias.
Various sorts of defects can change dramatically the overall properties and macroscopic behavior of crystalline solids. Particular types of dominating defects vary from one large class of materials to another. It has been known for a long time that vacancies are especially important in ceramic materials [5]–[9]. Effec
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