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Effect of surface charges on the polarization of BaTiO 3 thin films investigated by UHV ‐ SPM
Author(s) -
Suzuki Keigo,
Hosokura Tadasu,
Okamoto Takafumi,
Steffes James,
Murayama Koji,
Tanaka Nobuhiko,
Huey Bryan D.
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15734
Subject(s) - piezoresponse force microscopy , materials science , thin film , nanocrystalline material , kelvin probe force microscope , crystallite , ferroelectricity , scanning probe microscopy , nanotechnology , microstructure , hysteresis , work function , polarization (electrochemistry) , composite material , optoelectronics , atomic force microscopy , condensed matter physics , chemistry , dielectric , physics , metallurgy , layer (electronics)
Nanostructured BaTiO 3 polar thin films are increasingly critical to the function of future multilayer ceramic capacitors and related oxide‐based electronic devices. The effect of surface charges on BaTiO 3 polarization behavior is therefore investigated by ultra‐high vacuum scanning probe microscopy ( UHV ‐ SPM ) for 3 distinct morphologies—epitaxial, polycrystalline, and nanocrystalline films. Regardless of the film morphology, Kelvin probe force microscopy reveals that BaTiO 3 thin film surfaces exhibit positive charging after contact scanning by various noble AFM probes due to the work function difference between tip and specimen. According to piezoresponse force microscopy, these positive charges uniformly stabilize downward polarized domains. However, the hysteresis and concomitant surface charging behavior are strongly sensitive to microstructure and defects. In particular, the stability and switching behavior are influenced by bulk and interfacial defect distributions and hence correlated to film deposition methods and grain size. Such morphology dependent properties for BaTiO 3 films are revealed only through UHV measurements where screening charges from the ambient can be minimized, demonstrating the importance of UHV ‐ SPM for understanding ferroelectric thin films and nanostructures.