Direct Growth of Magnetic Non-van der Waals Cr₂X₃(X = S, Se, and Te) on SiO₂/Si Substrates through the Promotion of KOH

Two-dimensional (2D) magnetic materials can be used to construct multifunctional electronic and spintronic devices attributed to their unique 2D restricted magnetic properties. However, some magnetic materials are non-van der Waals materials, and the substrate used in chemical vapor deposition (CVD) is usually a van der Waals substrate like mica. This kind of substrate can cause transfer problems and increase the complexity of equipment fabrication or magnetic measurement. It is meaningful to further optimize the current production process for realizing good repeatability and simple fabrication. Growing materials on SiO2/Si can directly make electronic devices and measure magnetic properties. Herein, we use potassium hydroxide to modify a SiO2/Si substrate and succeed in growing Cr2X3 (X = S, Se, and Te) directly on the SiO2/Si surface by a CVD method. OH– is attached to the surface of SiO2/Si, thereby inhibiting the growth of thin layered Cr2X3 along the [001] zone axis. Through density function theory calculation, it is verified that the formation energy of Cr2S3 and SiO2/Si heterojunction can be enlarged by introducing OH–, which is beneficial to the growth of Cr2X3 on the SiO2/Si surface. At the same time, we have also achieved Cr2S3 and Cr2Se3 with controlled size and thickness. The thinnest thickness of the three materials on SiO2/Si can be close to 1 unit cell. Cr2S3, Cr2Se3, and Cr2Te3 nanosheets exhibit ferrimagnetic, spin glass, and ferromagnetic behavior, respectively. This work can provide a new method for the growth of non-van der Waals 2D materials on SiO2/Si, and it is of great significance to the fabrication of spintronic devices.