IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Tuesday Sessions
       Session SS3-TuP

Paper SS3-TuP15
Spatially Resolved Thermodynamic and Kinetics of Adsorption on BaTiO@sub 3@ Surface by Variable Temperature Scanning Probe Microscopy

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Adsorption/Desorption Poster Session
Presenter: S. Gupta, University of Pennsylvania
Authors: S.V. Kalinin, University of Pennsylvania
D.A. Bonnell, University of Pennsylvania
S. Gupta, University of Pennsylvania
Correspondent: Click to Email
Variable temperature scanning surface potential microscopy is used to determine thermodynamic and kinetic parameters associated with polarization and charge dynamics on BaTiO@sub 3@ (100) surface. Potential retention above the ferroelectric phase transition, observation of domain wall motion, and local piezoresponse indicate that the temperature dependence of surface potential results from the interplay between the fast dynamics of atomic polarization and slower dynamics of screening charge. At room temperature surface potential has the sign of the screening charges and is reverse to that expected from polarization orientation. Increasing the temperature results in a decrease of polarization charge leaving the screening charges uncompensated, thus increasing the effective surface potential. On decreasing the temperature spontaneous polarization increases and for a short period of time sign of domain potential is determined by the polarization charge. This phenomenon is referred to as temperature induced potential inversion (TIPI). Under isothermal conditions, polarization and screening charges equilibrate and the potential returns to an equilibrium value. The relaxation kinetics are found to be weakly dependent on temperature with activation energy E@sub a@ ~ 4 kJ/mole. The equilibrium domain potential difference was found to be linearly dependent on temperature. A thermodynamic description of ferroelectric screening based on the Ginzburg-Devonshire theory was developed and enthalpy and entropy were obtained as @Delta@H@sub ads@ = 164.6 kJ/mole, @Delta@S@sub ads@ = -126.6 J/mole K for BaTiO@sub 3@ (100) surface in air. These values are within the range expected for adsorption from the gas phase. Thus, in the case where the charge compensation mechanism is surface adsorption, scanning probe microscopy allows kinetics and thermodynamics of adsorption to be studied with the advantage of spatial localization over techniques such as temperature programmed desorbtion.