Epitaxial Thin Films of Y doped HfO$_{\mathrm{2}}$

Hafnium oxide (HfO$_{\mathrm{2}})$ is one of a few metal oxides that is thermodynamically stable on silicon and silicon oxide. There has been renewed interest in HfO$_{\mathrm{2}}$ due to the recent discovery of ferroelectricity and antiferroelectricity in doped HfO$_{\mathrm{2}}$. Typical ferroelectrics -- such as strontium bismuth tantalate (SBT) and lead zirconium titanate (PZT) -- contain elements that easily react with silicon and silicon oxide at elevated temperatures; therefore, such ferroelectrics are not suited for device applications. Meanwhile, ferroelectric HfO$_{\mathrm{2}}$ offers promise regarding integration with silicon. The stable phase of HfO$_{\mathrm{2}}$ at room temperature is monoclinic, but HfO2 can be stabilized in the tetragonal, orthorhombic or even cubic phase by suitable doping. We stabilized Y-doped HfO2 thin films using pulsed laser deposition. The strain state can be controlled using various perovskite substrates and controlled growth conditions. We report on Y-doped HfO2 domain structures from piezo-response force microscopy (PFM) and structural parameters via X-ray reciprocal space maps (RSM). We hope this work spurs further interest in strain-tuned ferroelectricity in doped HfO2.