Recent advances in synthesis of two-dimensional non-van der Waals ferromagnetic materials

Due to their strong covalent binding interaction between adjacent layers, it was difficult to exfoliate non-layered materials compared to layered materials. Recently, Balan, et al. (Nat. Nanotechnol. 13, 602–609, 2018) prepared a non-van der Waals (non-vdW) two-dimensional (2D) hematene from hematite (α-Fe₂O₃) by liquid exfoliation. Subsequently, various approaches including chemical vapor deposition (CVD), molecular beam epitaxy (MBE), ion layer epitaxy (ILE), pulsed laser deposition (PLD), and polymer assisted deposition (PAD) have been developed. Notably, a general thermodynamics-triggered competitive growth (TTCG) model was proposed to design a new hydrate-assisted CVD (HACVD) of the 2D non-layered materials growth. Although existing methods have achieved some good results, there are still many obstacles to overcome. In this review, we aim to give an overview on the recent advances and challenges in synthesis of 2D non-vdW ferromagnetic materials, and future prospects of 2D non-layered materials.