Surface-adsorbed polar molecules can significantly alter the ferroelectric properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelectric thin film devices, such as ferroelectric tunnel junctions. Herein, we report an imprint control of BaTiO3 (BTO) thin films by chemically induced surface polarization pinning in the top few atomic layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod analysis demonstrate that the chemically induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelectric phase in BTO tunnel junctions. We conclude that the chemical treatment of ferroelectric thin films with polar molecules may serve as a simple yet powerful strategy to enhance functional properties of ferroelectric tunnel junctions for their practical applications.
Bibliographical noteFunding Information:
The work at University of Wisconsin-Madison was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering, under Award DE-FG02-06ER46327 (fabrication and structural and surface characterization of thin films). The research at University of Nebraska-Lincoln was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering, under Award DE-SC0004876 (PFM measurements), and by the National Science Foundation (NSF) through Materials Research Science and Engineering Center (MRSEC) under Grant DMR-1420645 (theoretical modeling).
- Imprint control
- ferroelectric thin films
- ferroelectric tunnel junctions
- surface chemistry
- water adsorption