computer simulations of ferroelectric local switching by phase-field approach

Open Access
Author:
Duan, Chen
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 31, 2012
Committee Members:
  • Long Qing Chen, Thesis Advisor
Keywords:
  • ferroelectric phase-field approach
Abstract:
Ferroelectric materials are a class of important functional materials with wide applications in various fields, e.g., microelectronics, storage devices, sensors and actuators. The switching behaviors of ferroelectrics with applied electric field are fundamental to the storage applications. The traditional phenomenological thermodynamics is mainly based on perfect crystal model, which cannot properly describe the effect of ferroelectric domain wall as well as other defects. Besides, it cannot describe the switching with applied inhomogeneous electric field, which would be important to the nanoscale switching phenomena of with the tip of piezoresponse force microscopy (PFM). Phase-field approach is a very powerful tool to model the microstructure evolution processes. In this work, a three-dimension phase-field model was developed to predict the nanoscale switching of ferroelectric thin film induced by the PFM tip. The nucleation mechanisms of reversal domain induced by the tip were intensively discussed which include the effects of a-c twinned domain wall and 180-degree domain wall. It is found that the effects are distance-dependent and the interaction between tip and a-c twinned domain wall is asymmetrical on the two sides. Besides, the mechanical effect induced by the PFM tip was also included, and the possibility of switching a single domain solely by mechanical means was confirmed, which may need further experimental confirmation.