BaTiO₃ Nanostructures on Si Fabricated by Neon Ion Milling

Ferroelectric nanostructures are of great interest for fundamental studies on scaling effects of ferroelectricity and as building blocks for ferroelectric-based nanoscale devices for low power, high density integrated circuits. In this study, we investigate the ferroelectric properties of BaTiO₃ cylindrical nanostructures on Si. Epitaxial BaTiO₃thin films were grown by molecular beam epitaxy on SrTiO₃-buffered Si (100) substrates Nanopillars with different lateral dimensions (from 200 - 500 nm) were then fabricated using focused neon ion milling in a Zeiss Orion Nanofab microscope¹. The unpatterned thin films were first characterized using X-ray diffraction, Raman spectroscopy, and piezoresponse force microscopy (PFM) showing <i>c</i>- axis orientation and a ferroelectric behaviour. Ferroelectricity in the neon ion milled nanostructures was investigated using band excitation piezoresponse force microscopy (BE-PFM)² and contact Kelvin probe force microscopy (cKPFM)³. Their crystalline structure, strain state, and polarization were studied at a local scale by scanning/transmission electron microscopy (S/TEM). We find an imprint and a maximal switchable response in the nanostructures that are dependent on their lateral dimension. The information gained from S/TEM will be discussed, emphasizing the effect of the pillar lateral dimensions on the polarization state. Finally, the potential damage caused by the ions during milling will be evaluated.<br/><br/><b>References</b><br/>1. Olanyian, I. <i>et al.</i> Nanofabrication of barium titanate using noble gas ions, submitted 2022.<br/>2. Jesse, S., <i>et al.</i>, The band excitation method in scanning probe microscopy for rapid mapping of energy dissipation on the nanoscale. <i>Nanotechnology</i> <b>18</b>, 435503 (2007).<br/>3. Balke, N. <i>et al.</i> Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy. <i>ACS Nano</i> <b>9</b>, 6484–6492 (2015).