▎ 摘　　要

The elimination of wrinkles has become a research hotspot in the realm of the chemical vapor deposition growth of graphene, and there have been reliable routes developed for the scenario of catalytic synthesis on metals. Nonetheless, the transfer-free growth of graphene over insulating substrates affording ultra-flatness remains a puzzle. Here, the authors report the direct preparation of ultra-flat graphene on an economical quartz glass substrate at a wafer level, without any wrinkles and metallic impurities, is reported. Density functional theory calculations are employed to establish that graphene adlayer is prone to generate in the presence of textured particulates. In parallel, a critical temperature regime (1443-1453 K), is identified within which graphene adlayer-restrained forming and substrate in-situ flattening could simultaneously occur. The thus-obtained graphene enables the atomically smooth growth of a GaN film with (001) single-crystallinity over the amorphous substrate. This technique is particularly attractive in the context of cost-effective integration of emerging III-nitrides toward exciting applications.