'Dream Material' Graphene, Freely Adjustable Number of Layers

[Asia Economy Reporter Junho Hwang] Domestic researchers have developed a technology that can freely control the number of layers of graphene, known as the dream material, up to four layers. Depending on the number of graphene layers, the miniaturization of integrated circuits and the adjustment of the semiconductor bandgap can be achieved. It is expected to be utilized in high-integration semiconductor electrodes and various photoelectrode devices in the future.

Lee Young-hee, head of the Nano-Structure Physics Research Group at the Institute for Basic Science, along with Samsung Advanced Institute of Technology and Pusan National University, announced on the 28th that their joint research team developed a method to grow multilayer graphene up to four layers as a single crystal, and the research results were recently introduced in Nature Technology.

Graphene is formed by decomposing and adsorbing hydrocarbons injected through a thin metal film catalyst. When metals with low solubility, such as copper, are used, monolayer graphene is formed, and when metals with high solubility, such as nickel, are used, multilayer graphene is formed. However, a technical limitation was that the number of layers in multilayer graphene was not uniform.

Schematic Diagram of Multilayer Graphene Growth via Copper-Silicon Alloy

The research team overcame this limitation by creating a copper-silicon alloy to increase carbon solubility. When methane gas is injected into this alloy, carbon atoms from methane and silicon atoms from the metal substrate meet to form a uniform silicon-carbon layer. This layer controls the carbon solubility of the copper-silicon alloy. Co-first author Dr. Banruen Nguyen from Samsung Advanced Institute of Technology explained, "It took two years of trial and error from coming up with the idea to finding a method to produce a uniform silicon-carbon layer."

Using the substrate made from the alloy developed by the research team, uniform multilayer graphene from 1 to 4 layers was produced. The number of layers could also be controlled depending on the methane concentration. The research team stated, "Each layer overlapped at exactly the same angle and was formed at a size comparable to semiconductor wafers," and added, "this is the first study to synthesize large-area, high-quality multilayer graphene up to four layers."

Research group leader Lee Young-hee emphasized the significance by stating, "This experiment demonstrated that uniform multilayer graphene growth is possible using chemical vapor deposition."

Electron microscope images of graphene from the 1st to 4th floor

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