Abstract
Reducing the dimensions of ferroelectric materials down to the nanoscale has strong implications on the ferroelectric polarization pattern and on the ability to switch the polarization. As the size of ferroelectric domains shrinks to the nanometer scale, the heterogeneity of the polarization pattern becomes increasingly pronounced, enabling a large variety of possible polar textures in nanocrystalline and nanocomposite materials. Critical to the understanding of fundamental physics of such materials and hence their applications in electronic nanodevices is the ability to investigate their ferroelectric polarization at the nanoscale in a nondestructive way. We show that contact Kelvin probe force microscopy (cKPFM) combined with a k-means response clustering algorithm enables to measure the ferroelectric response at a mapping resolution of 8 nm. In a BaTiO3 thin film on silicon composed of tetragonal and hexagonal nanocrystals, we determine a nanoscale lateral distribution of discrete ferroelectric response clusters, fully consistent with the nanostructure determined by transmission electron microscopy. Moreover, we apply this data clustering method to the cKPFM responses measured at different temperatures, which allows us to follow the corresponding change in the polarization pattern as the Curie temperature is approached and across the phase transition. This work opens up perspectives for mapping complex ferroelectric polarization textures such as curled/swirled polar textures that can be stabilized in epitaxial heterostructures and more generally for mapping the polar domain distribution of any spatially highly heterogeneous ferroelectric materials.
Original language | English |
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Pages (from-to) | 4409-4417 |
Number of pages | 9 |
Journal | ACS Applied Electronic Materials |
Volume | 3 |
Issue number | 10 |
DOIs | |
State | Published - Oct 26 2021 |
Funding
C.D. acknowledges Martin Franck and Vijay Narayanan from IBM in Yorktown Height, NY, USA, for providing the pre-structured Si wafer and Lucie Mazet for the growth of the sample at the technology platform “NanoLyon” of INL/Ecole Centrale de Lyon, Ecully, France. C.D. and S.W.S. acknowledge access to the Center for Nanophase Materials Sciences through the proposals CNMS2018-298 and CNMS2020-B-00356 and thank Nina Balke for support and useful discussions. This effort (STEM) is based upon work supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division (A.B.). The PFM portion of this work was performed at and supported by (SVK, RKV) the Center for Nanophase Materials Sciences, a US DOE Office of Science User Facility.
Keywords
- BaTiO
- contact Kelvin probe force microscopy
- ferroelectricity
- heterogeneous materials
- k-means clustering
- machine learning
- nanoscale domains