Chemical vapor deposition epitaxial growth of graphene single crystal wafers

Chemical vapor deposition (CVD) epitaxial growth of graphene single crystal wafers is a technique for preparing high-quality graphene single crystals on substrates. The following are the key steps and key points of the process:

1. Substrate selection

Common substrates include:

Copper (Cu): Suitable for high-quality graphene growth, the low solubility of carbon in copper helps the formation of single-layer graphene.

Nickel (Ni): The high solubility of carbon in nickel may lead to multi-layer graphene, but single crystals can still be prepared by controlling the conditions.

2. Precursor selection

The commonly used precursor is methane (CH₄), and others such as ethylene (C₂H₄) and acetylene (C₂H₂) can also be used.

3. Growth process

Pretreatment: The substrate needs to be cleaned and annealed to remove impurities and smooth the surface.

Growth stage: At high temperature (usually 900°C-1000°C), hydrogen and carbon source gas are introduced, hydrogen acts as a reducing agent and carrier gas, and the carbon source gas decomposes and forms graphene on the substrate surface.

Cooling: After the growth is completed, slow cooling is performed to prevent the graphene from cracking or deforming.

4. Key parameters

Temperature: High temperature promotes the decomposition of the carbon source and the crystallization of graphene.

Gas ratio: The ratio of hydrogen to carbon source gas affects the quality and number of graphene layers.

Pressure: Low pressure environment contributes to the growth of high-quality graphene.

5. Epitaxial growth mechanism

Surface catalysis: The substrate surface catalyzes the decomposition of the carbon source, and carbon atoms diffuse on the surface and form a graphene lattice.

Lattice matching: The degree of lattice matching between the substrate and graphene affects the quality of epitaxial growth.

6. Post-processing

Transfer: Transferring graphene from the growth substrate to the target substrate, usually by wet or dry transfer.

Characterization: Characterize the quality and structure of graphene by Raman spectroscopy, AFM, SEM and other means.

7. Application

High-quality graphene single crystals are widely used in electronic devices, sensors, composite materials and other fields.

Summary

The key to preparing graphene single crystal wafers by CVD epitaxial growth lies in substrate selection, precursor control, growth parameter optimization and post-processing. This technology provides a reliable way for the large-scale application of graphene.