Persistence of Surface Domain Structures for a Bulk Ferroelectric aboveTC

Abstract

Photoemission electron microscopy performed on a well-prepared surface of BaTiO3 reveals the persistence of surface domains at temperatures well above the bulk Curie temperature. Their patterns follow the ferroelectric domain structure observed at 300 K. The contrast between formerly outward polarized domains and in-plane polarized domains is preserved across the transition, while the contrast of inward polarized domains changes sign. The work functions of different possible structures are compared by first-principles calculations. The domain contrast in photoemission above the bulk Curie temperature is associated with a remaining tetragonal distortion of the topmost unit cells which is stabilized by an ionic surface relaxation.

Effect of Internal Electric Fields on Charge Carrier Dynamics in a Ferroelectric Material for Solar Energy Conversion

“…Photo electron emission spectroscopy studies have indicated a 30% loss of band bending of BaTiO 3 during heating in the tetragonal phase below T C . [ 40 ] Such dependencies of P S and surface potential upon temperature have also been supported by theoretical modeling based on treating the ferroelectric medium as a polar semiconductor. [ 41 ] Regarding the absolute magnitude of the band bending in BaTiO 3 resulting from P S , reported values at room temperature measured under vacuum conditions are of the order of 1.3 V in total or 0.65 V at each interface.…”

“…[ 41 ] Regarding the absolute magnitude of the band bending in BaTiO 3 resulting from P S , reported values at room temperature measured under vacuum conditions are of the order of 1.3 V in total or 0.65 V at each interface. [ 40 ] We note that band bending is typically reduced under atmospheric conditions, such as those employed herein, by external screening due to molecular chemisorption to the BaTiO 3 surface. [ 42 ] In our case, the illumination of the surface of the ferroelectric is likely to reduce such screening.…”

X-ray photoelectron diffraction study of relaxation and rumpling of ferroelectric domains in BaTiO3(001)

“…Not only does the XPD allow quantification of the local surface atomic distortions, it also points to the simultaneous presence of different surface polarizations. Similar information has also been obtained using photoelectron emission microscopy 33,34 (PEEM) and low-energy electron microscopy 25 (LEEM), however, the real-space imaging mode of these techniques does not allow direct probing of the microscopic atomic distortion. To do so would require LEEM imaging of the diffraction plane of the microscope in order to carry out a quantitative micro-LEED I-V experiment, giving similar information to that obtained by XPD, albeit without the chemical sensitivity of the latter.…”

Ultrathin Perovskites: From Bulk Structures to New Interface Concepts

“…These local work function differences can be used to image the ferroelectric domain structure at the nanoscale by photoelectron emission microscopy (PEEM). In a temperaturedependent PEEM study, Höfer et al could demonstrate that the domain contrast is preserved at the surface of a BaTiO 3 (001) single crystal up to a temperature of 510 K, which is nearly 100 K above the bulk ferroelectric to paraelectric phase transition temperature T C [29]. Their calculations revealed that the surface relaxation stabilizes the tetragonal distortion of the surface-near domains on top of a paraelectric bulk.…”