AVS 47th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL+MS-ThA

Paper DI+EL+MS-ThA4
Atomic Polarization and Screening Charge by Variable Temperature Scanning Probe Microscopy of Ferroelectric Surfaces

Thursday, October 5, 2000, 3:00 pm, Room 312

Session: High K Dielectrics: Perovskites
Presenter: S.V. Kalinin, University of Pennsylvania
Authors: S.V. Kalinin, University of Pennsylvania
D.A. Bonnell, University of Pennsylvania
Correspondent: Click to Email
Atomic force microscopy (AFM), electrostatic force microscopy (EFM), scanning surface potential microscopy (SSPM) and piezoresponse imaging (PRI) are applied to the BaTiO3 (100) phase transition. The imaging mechanism for non-contact microscopies (EFM and SSPM) based on an analytical solution for potential and field above the surface is discussed. The PRI imaging mechanism on a ferroelectric surface is analyzed in terms of the solution of the combined electrostatic-piezoelectric indentation problem. The relationship between SPM signal and screened and unscreened charge density is established. Quantification of force and force gradient-distance dependencies indicate that polarization bound charge is screened on this surface when imaged in ambient environments. The absolute value of the measured potential difference between domains of opposite polarity suggests that surface adsorbates play the governing role in surface potential. This conclusion is corroborated by a direct measurement of the phase transition and by observations of domain wall motion. The influence of tip shape effects and mobile surface charges on effective domain wall width is also discussed. The contribution of electrostatic forces to piezoresponse contrast is extracted from force-distance measurements and its influence of the local hysteresis loops is estimated. Considerations regarding the polarization switching by the tip are presented. Based on the experimental observations for this and other systems the dominant role of electromechanical vs. electrostatic effects in PRI imaging mechanism is established.