Photoinduced patterning of oxygen vacancies to promote the ferroelectric phase of Hf_0.5Zr_0.5O₂

Photoinduced reductions in the oxygen vacancy concentration were leveraged to increase the ferroelectric phase fraction of Hf_0.5Zr_0.5O₂ thin-films. Modest (⁠ $∼ 2 − 77 pJ / cm 2$⁠) laser doses of visible light (488 nm, 2.54 eV) spatially patterned the concentration of oxygen vacancies as monitored by photoluminescence imaging. Local, tip-based, near-field, nanoFTIR measurements showed that the photoinduced oxygen vacancy concentration reduction promoted formation of the ferroelectric phase (space group $Pca 2 1$⁠), resulting in an increase in the piezoelectric response measured by piezoresponse force microscopy. Photoinduced vacancy tailoring provides, therefore, a spatially prescriptive, post-synthesis, and low-entry method to modify phase in HfO₂-based materials.