New technology may produce wrinkle-free graphene

The existing CVD technology forms many wrinkles during the growth of graphene, which greatly reduces the thermal conductivity and electrical conductivity of the graphene material, thereby impairing the performance of the graphene electronic device. Recently, Zhongfan Liu and Hailin Peng from the Nanochemistry Center of Peking University have developed a new technology that can produce high-quality graphene through well-designed substrates without the troublesome folds often formed during conventional growth. The ultra-smooth graphene material grown by this technique is greatly improved in electrical properties compared to the pleated graphene grown by conventional methods.

In theory, raw graphene materials have the highest electrical, thermal, and mechanical properties that can be used to make fast, energy-efficient electronics and optics. However, in practice, it is very difficult to grow a large number of single crystal super-smooth graphene suitable for high-performance electronic devices. The existing CVD technology forms many wrinkles during the growth of graphene, which greatly reduces the thermal conductivity and electrical conductivity of the graphene material, thereby impairing the performance of the graphene electronic device.

Recently, Zhongfan Liu and Hailin Peng from the Nanochemistry Center of Peking University have developed a new technology that can produce high-quality graphene through well-designed substrates without the troublesome folds often formed during conventional growth. . The ultra-smooth graphene material grown by this technique is greatly improved in electrical properties compared to the pleated graphene grown by conventional methods. The relevant results were published in the journal "ACSNano". (ACSNano 2017, DOI: 10.1021/acsnano. 7b06196).

Existing CVD techniques typically use copper foil as the growth substrate to form large ultra-thin graphene sheets. However, Hailin Peng, a nanochemist at Peking University, and colleagues speculated that the mismatch in material properties between graphene and copper growth substrates could cause graphene wrinkles. Graphene and copper (100), the crystalline form of copper commonly used to grow it, expand at different rates at a given temperature, causing mechanical strain and causing wrinkling. Therefore, Peng and his colleagues searched for a copper substrate with a better crystal structure. They now report that the graphene grown on the Cu (111) film is very smooth. More importantly, its electron mobility is a measure of the movement of current in material, can be up to 11,000 cm²V-1s-1. This is the highest level achieved by graphene grown in large areas using practical methods. The team used a 10 cm sapphire wafer as a support to grow a Cu (111) film with a suitable crystal structure. After the graphene is transferred, the copper-sapphire wafer can be reused. Peng said that this method can be compatible with the technology used in the semiconductor industry. The next step is manufacturing. He said: "We are working hard to achieve mass production of this wrinkle-free single-crystal graphene.

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