Dr. Sebastian Schmitt: "Investigation of BaTiO3 nanostructures on silicon by scanning probe microscopies"
Helmholtz Centre for Materials and Energy, Germany
A high-density integration of ferroelectric enabled on-chip circuitry requires the downscaling of ferroelectric materials. However, the size, configuration, and stability of electrically switchable polarization domains, which are the key features of a nanoscopic ferroelectric building block, are highly dependent on its geometry, and the electrical and chemical surface boundary conditions1–3. In this study, we investigate the ferroelectric properties of barium titanate (BaTiO3) cylindrical nanostructures on strontium titanate (SrTiO3) buffered silicon (Si) of different geometries with and without different top electrodes. Using focused Neon (Ne) ion beam milling in an ion microscope or reactive ion etching (RIE), the BaTiO3 structures were fabricated by the patterning of molecular beam epitaxy (MBE) grown thin films with or without sputtered metal electrodes. By the means of modern scanning probe microscopy (SPM) methods such as switching spectroscopy and band excitation piezoresponse force microscopy (SS-PFM, BE-PFM) or contact Kelvin probe force microscopy (cKPFM), we show how ferroelectric domain patterns and switching properties evolve as function of structure size, geometry, electrode material and environmental conditions such as temperature. The results yield fundamental insights into the formation and stabilization of ferroelectric domains and domain textures in nanoscale structures and capacitors, which are of relevance for the understanding of the investigated material system as well as for its technological applications.
1. Ahn, C. H., Rabe, K. M. & Triscone, J. M. Ferroelectricity at the Nanoscale: Local Polarization in Oxide Thin Films and Heterostructures. Science. 303, 488–491 (2004).
2. Gruverman, A. & Kholkin, A. Nanoscale ferroelectrics: Processing, characterization and future trends. Reports Prog. Phys. 69, 2443–2474 (2006).
3. Ihlefeld, J. F. et al. Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations. J. Am. Ceram. Soc. 99, 2537–2557 (2016).