High quality large-area single crystal copper substrate is an effective method for preparing high-quality large-area single crystal graphene. There are several main methods for preparing single crystal copper: 1) Commercial single crystal copper is mostly produced by using the high-temperature hot casting mode continuous casting method to produce single crystal copper columns, and the production cost of single crystal copper foil is relatively high; 2) Using a single crystal sapphire substrate as a template, copper thin film was deposited and the surface of single crystal copper (111) was obtained through high-temperature annealing; 3) Similar to the method of preparing monocrystalline silicon, single crystal copper is prepared by introducing single crystal copper seeds and using the Czochralski technique. Among them, PAM-XIAMEN can provide sapphire based copper thin films for epitaxial growth of single crystal graphene, with specific specifications as follows:

1. Specification of Copper Thin Film on Sapphire Substrate

PAM240220 – COS

2. Single Crystal Graphene Growth on Copper Film

Most graphene based electronic devices require insulation support. However, high-quality graphene films for industrial use are typically grown on metal substrates (such as copper thin film) and then transferred to insulating supports for device manufacturing.

Researchers transformed polycrystalline copper foil into single crystal (111) copper thin film deposition on the surface of sapphire, and introduced active carbon atoms from the metal substrate to catalyze methane decomposition on the resulting thin film. Carbon atoms diffuse towards the copper/sapphire interface acting as a template through a metal film, forming well oriented graphene islands. After several growth cycles, these graphene islands merge to form thin films.

Then, researchers used hydrogen argon plasma to etch away any graphene stacked on top of the copper film to promote carbon diffusion. They immersed the sample in liquid nitrogen and quickly heated it to 500℃, making the copper thin film materials easy to peel off while maintaining the integrity of the single crystal graphene monolayer on sapphire substrate. 

In this way, field-effect transistors manufactured on single crystal graphene monolayers grown on sapphire exhibit excellent performance and higher carrier mobility since its excellent electronic properties due to the high crystallinity and fewer surface wrinkles. This work breaks the bottleneck of synthesizing wafer level single crystal monolayer graphene on insulating substrates and may drive the development of next-generation graphene based nanodevices.

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