The mechanism of CVD graphene involves a two-step process: dissolution and segregation.
What is the Mechanism of CVD Graphene? 5 Key Steps Explained
1. Dissolution
In the first step, carbon atoms are diluted or incorporated into a transition metal catalyst, such as nickel, copper, platinum, or iridium.
This process is known as dissolution.
The carbon atoms diffuse into the metal substrate, driven by high temperatures within the substrate.
The higher the temperature, the faster the diffusion process occurs.
The duration of time also plays a role, as carbon atoms need additional time to reach their saturated state in thicker metal films.
2. Segregation
In the second step, known as segregation, the carbon atoms rapidly cool down, causing them to separate from the metal substrate and form a graphene layer.
This rapid cooling can be achieved by reducing the temperature or by using a cooling agent.
The carbon species that have diffused into the metal substrate react with each other to form small carbon clusters.
Once these clusters exceed a critical size, graphene crystals nucleate and grow on the catalyst surface.
3. Deposition of Carbon-Bearing Gases
The process of CVD graphene involves the deposition of carbon-bearing gases on a metallic surface within a heated reaction chamber.
The metal catalyst acts as both a catalyst for the decomposition of the carbon species and as a surface for the nucleation of the graphene lattice.
4. Monitoring Critical Conditions
The temperature, pressure, duration of time, and other conditions must be carefully monitored to ensure the successful growth of graphene.
5. Formation of Graphene Crystals
The carbon precursors, such as methane, are converted into graphene on a metal catalyst surface, such as copper, through decomposition and formation of carbon clusters.
The CVD reaction typically occurs at high temperatures, around 1000 °C.
Once the carbon clusters exceed a critical size, graphene crystals nucleate and grow, forming a single atom-thick layer of carbon atoms.
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