Engineering phase transition and ferroelectric properties in acceptor-doped HfO2/SrRuO3 thin-film heterostructures by a charge-balance synergistic strategy

In HfO 2 , the stabilization of orthorhombic phase is crucial for hafnia-based ferroelectric devices. Here, we propose a charge-balance synergistic strategy to modulate phase transition and optimize ferroelectric properties in acceptor-doped HfO 2 thin-film heterostructures. Sm-doped HfO 2 /SrRuO 3 heterostructures are adopted as the platform, in which the acceptor Sm Hf ′ introduces extra holes into the HfO 2 controlled by doping concentration, while the SrRuO 3 electrode injects electrons depended on termination-controlled surface work function. Transition from monoclinic to orthorhombic and then to tetragonal phase is observed with increasing Sm concentration. The Sm-doping region for improved ferroelectricity is found to be depended on SrRuO 3 termination. These behaviors are ascribed to the charge-balance effect that combines the acceptor doping and the interface injection in the heterostructures. The holes in HfO 2 lattices are thus modulated to dominantly distribute on specific oxygen sublattices, lowering the relative energy between monoclinic and orthorhombic phases. We also extend the study into other acceptor-doped HfO 2 , such as La 3+ and Eu 3+ , and observe almost identical phase transition and ferroelectric behaviors. Our findings provide more physical insights into the stabilization of orthorhombic phase and open a new gateway for designing high-performance ferroelectric HfO 2 devices by harnessing both the electrode structures and the HfO 2 -based layers in heterostructure systems. • Charge-balance synergistic strategy modulates phase transition and optimizes ferroelectricity in doped HfO 2 films. • Electron injection and hole doping together yield high ratio of orthorhombic phase. • Ln-doped HfO 2 films show universal phase transition and improved ferroelectric properties.