Solution Synthesis of Layered van der Waals (vdW) Ferromagnetic CrGeTe₃ Nanosheets from a Non-vdW Cr₂Te₃Template

Abstract

CrGeTe₃ has recently emerged as a new class of two-dimensional (2D) materials due to its intrinsic long-range ferromagnetic order. However, almost all the reported synthesis methods for CrGeTe₃ nanosheets are based on the conventional mechanical exfoliation from single-crystalline CrGeTe₃, which is prepared by the complicated self-flux technique. Here we report a solution-processed synthesis of CrGeTe₃ nanosheets from a non-van der Waals (vdW) Cr₂Te₃ template. This structure evolution from non-vdW to vdW is originated from the substitution of Ge atoms on the Cr sites surrounded by fewer Te atoms in the Cr₂Te₃ lattice due to their smaller steric hindrance and lower energy barrier. These CrGeTe₃ nanosheets present regular hexagonal structures with a diameter larger than 1 μm and excellent stability. They exhibit soft magnetic behavior with a Curie temperature lower than 67.5 K. This non-vdW to vdW synthesis strategy promotes the development of CrGeTe₃ in ferromagnetism while providing an effective route to synthesize other 2D materials.