Fabrication by neon ion milling and ferroelectricity of BaTiO3 nanodisks on silicon

Israel Ibukun Olaniyan ^1,2 Dong Jik Kim ¹ Jürgen Albert ¹ Haidong Lu ⁴ Beatriz Rodrigues Canabarro ³ Daniel Abou-Ras ¹ Veeresh Deshpande ¹ Teresa Hungria ⁵ César Magen ^6,7 Sylvie Schamm-Chardon ³ Sebastian Schmitt ¹ Alexei Gruverman ⁴ Catherine Dubourdieu ^1,2

¹Quantum Materials, Institute Functional Oxides for Energy-Efficient Information Technology, Helmholtz Zentrum Berlin, Berlin, Select a State or Province, Germany
²Physical Chemistry, Free University of Berlin, Berlin, Berlin, Germany
³CEMES, CNRS and Université de Toulouse, Toulouse, France
⁴Physics and Astronomy, University of Nebraska, Lincoln, USA
⁵Centre Raimond Castaing, Univ. de Toulouse, Toulouse, France
⁶Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, Zaragoza, Spain
⁷Instituto de Nanociencia y Materiales de Aragón, Universidad de Zaragoza, Zaragoza, Spain

Fundamental studies on ferroelectrics and advances in ferroelectric nanoelectronics require fabrication of ferroelectric nanostructures. Among the nanofabrication techniques, focused ion beam (FIB) milling offers the advantages of rapid prototyping and high precision and is widely applicable to different materials. When Ga ions are used for FIB milling of nanostructures a post-annealing process is often required to recover the damage induced by the ion bombardment after the fabrication of ferroelectric nanostructures[1]. Ne ions are lighter than Ga ones, which might be an advantage for mitigating milling damages. The development of He/Ne ion microscopes makes it possible to develop milling routes for the realization of nanostructures[2].

In this study, we investigated Neon FIB milling for the fabrication of BaTiO3 nanodisks on silicon. The nanostructures of diameter 500 nm down to 80 nm were fabricated from epitaxial BaTiO3 thin films grown by molecular beam epitaxy on SrTiO3-buffered Si (100) substrates. In order to protect the top of the BaTiO3 nanostructures, different metals were investigated (Au, W and Pt) as hard masks deposited prior to ion milling and removed afterwards. We characterized crystallinity, elemental composition, and microstructure of the nanodisks using scanning electron microscopy (SEM), electron dispersive X-ray spectrometry (EDX), electron backscatter diffraction (EBSD), and scanning transmission electron microscopy (STEM). The ferroelectric properties were investigated by piezoresponse force microscopy. Control of the structure dimensions, crystalline orientation, and damage of the nanodisks will be discussed. The ferroelectric properties of crystalline and amorphous nanodisks will be compared to the properties of the unpatterned thin films.

1. A. Schilling et al., Strategies for gallium removal after focused ion beam patterning of ferroelectric oxide nanostructures. Nanotechnology 18, (2007).

2. A. Grillo et al., High field-emission current density from b-Ga2O3 nanopillars, Appl. Phys. Lett. 114, 193101 (2019).