▎ 摘　　要

In recent years, graphene growth technology has been greatly progressed, and it is possible to grow graphene with millimeter-size single crystals using metal-catalysis CVD. However, the transfer process is unavoidably which largely deteriorates the graphene. We have proposed direct precipitation method of graphene using a W capping layer. The method does not only require a transfer process, but also the introduction of wrinkles will be suppressed by optimizing the cooling rate at the graphene precipitation. The growth conditions such as thickness of amorphous carbon, annealing temperature, cooling rate and crystallinity of Ni catalyst were systematically changed to study the mechanism of the precipitation method using the W cap layer. By the optimization of the conditions, wrinkle-free multilayer graphene with D/G ratio of less than 0.1 were successfully obtained directly on a sapphire substrate.