Van der Waals surface reconstruction for oriented epitaxial growth of two-dimensional metallic oxides.

Hybrid integration of two-dimensional single-crystalline metal oxides, including semiconductors, dielectrics, ferroelectrics and ferromagnetics, with silicon circuits enables functionalities such as spintronics and neuromorphic and quantum computing, forming a key part of the 'More-than-Moore' roadmap. However, synthesizing two-dimensional metal oxide single-crystal films has remained challenging. Here we report a van der Waals surface reconstruction of mica for the general large-scale, unidirectional growth of two-dimensional metal oxides (where M = Co, Fe, Ni, Mn) and their doped counterparts, which seamlessly coalesce into single-crystalline films. Quantum mechanics calculations reveal that reconstructing mica's oxygen atomic plane is critical for achieving the single-crystal epitaxy of these two-dimensional metal oxides. As an example, centimetre-scale two-dimensional Fe-doped CoO single-crystalline films were grown and exhibit room-temperature ferromagnetic semiconductor properties with a high Curie temperature of up to 430 K. These results demonstrate the power of this synthesis strategy, enabling the exploration of two-dimensional metal oxides for quantum physics and spintronics devices.