Coercive Field Control in Epitaxial Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films by Nanostructure Engineering

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Industry

Background:

• Ferroelectric hafnium oxide (HZO) is highly sought after in the semiconductor industry due to its CMOS compatibility and scalability.
• Key questions persist regarding the origins of ferroelectric phases and the tunability of HZO's properties.

Purpose of the Study:

• To investigate the impact of laser fluence on the coercive field (Ec) of HZO films.
• To understand the relationship between deposition energetics and the resulting microstructural and ferroelectric characteristics.

Main Methods:

• Pulsed laser deposition of 10 nm-thick epitaxial HZO films on SrTiO3 substrates.
• Systematic variation of laser fluence during film growth.
• Analysis of microstructural changes and measurement of coercive fields.
• Density functional theory (DFT) calculations to support experimental observations.

Main Results:

• Decreasing laser fluence from 1.3 J cm⁻² to 0.5 J cm⁻² reduced the coercive field (Ec) from ~3.3 to ~2.7 MV/cm.
• Lower laser fluence resulted in pure (111) oriented grains.
• Higher laser fluence led to an additional (11-1) orientation, creating low-angle tilt grain boundaries and dislocations that pin domains.

Conclusions:

• Lower energetic growth conditions, achieved with reduced laser fluence, are essential for obtaining low Ec in HZO films.
• Minimizing domain pinning sites through controlled growth is key for energy-efficient ferroelectric memory applications.