Ultra-thin plan-view lamella made by focused ion beam

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Microstructure dictates functional properties in advanced materials like ferroelectric hafnium zirconium oxide (HZO).
• Characterizing ultrathin HZO films is challenging due to nanoscale features and polymorphic variations.
• Conventional cross-sectional TEM sample preparation methods obscure critical microstructural details.

Purpose of the Study:

• To develop an optimized focused-ion-beam (FIB) workflow for preparing plan-view lamellae of ultrathin HZO films.
• To enable high-resolution microstructural and crystallographic analysis of HZO for ferroelectric device applications.
• To establish a robust method for correlating HZO microstructure with its ferroelectric performance.

Main Methods:

• A refined FIB workflow using a low-kV fine-thinning sequence for preparing electron-transparent plan-view lamellae from ~10 nm HZO films.
• In situ monitoring via scanning electron microscopy (SEM) and ex situ verification using energy-dispersive X-ray spectroscopy (EDS).
• Quantitative scanning transmission electron microscopy (STEM) with EDS to confirm lamella thickness and structural integrity.

Main Results:

• Successful fabrication of plan-view lamellae with a reproducible taper from 10 nm to 3-4 nm thickness at the edge.
• Minimized ion-induced damage and preserved atomic-column integrity in the thinned HZO films.
• Demonstrated capability for unambiguous polymorph identification using nanobeam electron diffraction (NBED).

Conclusions:

• The developed FIB workflow effectively prepares high-quality plan-view lamellae of ultrathin HZO films.
• This method overcomes limitations of conventional techniques, enabling detailed microstructural analysis.
• Provides a crucial platform for understanding and optimizing HZO-based ferroelectric materials and devices.