Since the emergence of graphene, families of two-dimensional materials with atomic level thickness, such as transition metal sulfides, black phosphorus, hexagonal boron nitride, etc., have sparked a global research boom due to their electrical, optical, thermal, and mechanical properties. However, how to achieve high-quality, large-area, and controllable preparation of these materials is the core challenge and cutting-edge field that drives them from basic research to practical applications.

At present, the preparation of two-dimensional materials mainly follows two technical routes: "top-down" and "bottom-up", each with its own characteristics and application scenarios:

1、 Top down method: mechanical peeling and liquid-phase peeling

1. Mechanical peeling: By repeatedly peeling off bulk crystals with adhesive tape, high-quality two-dimensional material sheets can be obtained, but with small size and extremely low yield, mainly used for basic physical property research.

2. Liquid phase exfoliation: dispersing bulk materials into layers in a specific solvent through ultrasound or shear force can achieve high yields and is suitable for the preparation of composite materials and slurries, but the resulting layer thickness is uneven and has many defects.

2、 Bottom up approach: chemical vapor deposition

This is the most promising path to achieve large-area, high-quality two-dimensional material preparation. The principle is to use chemical reactions of precursor gases (such as methane, metal organic sources) on high-temperature substrates (such as copper foil, sapphire) to "in-situ" nucleate atoms on the substrate surface and grow into two-dimensional thin films.

The advantage of CVD technology lies in its ability to prepare wafer level single crystal or high-quality polycrystalline thin films, which can be directly compatible with existing semiconductor processes and lay the foundation for building future electronic devices. Advanced CVD technology can also effectively reduce growth temperature and broaden substrate selection range through plasma assistance.

Despite significant progress, the controllable preparation of two-dimensional materials still faces many challenges:

1. Large area single crystal preparation: How to achieve large-scale, grain boundary free single crystal film growth on non single crystal substrates is a key challenge.

2. Accurate control of layers: achieving uniform and controllable growth of specific layers (especially single-layer) is still a research hotspot.

3. Non destructive transfer technology: transferring high-quality grown two-dimensional materials onto target functional substrates without introducing damage or contamination is a bottleneck in device fabrication.

4. Development and scaling of new materials: Exploring novel two-dimensional materials beyond MoS ₂ and developing scalable preparation methods.

The preparation technology of two-dimensional materials is a bridge connecting their magical properties with practical applications. Currently, this field is moving from initial exploration to precise control, from small laboratory samples to large-scale industrial production. Every breakthrough in preparation technology will open new doors for the application of two-dimensional materials in the next generation of electronics, optoelectronics, flexible devices, and other fields.