Gigantic-oxidative atomic-layer-by-layer epitaxy for artificially designed complex oxides.

Abstract

In designing material functionalities for transition metal oxides, lattice structure and d-orbital occupancy are key determinants. However, the modulation of these two factors is inherently limited by the need to balance thermodynamic stability, growth kinetics and stoichiometry precision, particularly for metastable phases. We introduce a methodology, namely gigantic-oxidative atomic-layer-by-layer epitaxy (GOALL-Epitaxy), to enhance oxidation power by three to four orders of magnitude beyond conventional pulsed laser deposition and oxide molecular beam epitaxy, while ensuring atomic-layer-by-layer growth of the designed complex structures. Thermodynamic stability is markedly augmented with stronger oxidation at elevated temperatures, whereas growth kinetics is sustained by using laser ablation at lower temperatures. We demonstrate the accurate growth of complex nickelates and cuprates-especially an artificially designed structure with alternating single and double NiO₂ layers that possess distinct nominal d-orbital occupancy, as a parent of the high-temperature superconductor. GOALL-Epitaxy enables material discovery within the vastly broadened growth parameter space.