Catalytic decomposition of SiO2 by Fe and the effect of Cu on the behavior of released Si species

Abstract Si supply mechanism in the spontaneous formation of SiO 2 pattern on a Cu foil, which was previously reported to enable the selective growth of graphene in no direct contact with organic materials, was investigated. Upon annealing at 1000 °C and atmospheric pressure, SiO 2 in the Fe-coated SiO 2 /Al 2 O 3 template covered by a Cu foil was found to be severely decomposed by Fe droplets. No signature of reaction between SiO 2 and Fe droplets suggested that Si species, which contributed to the spontaneous formation of SiO 2 pattern on a Cu foil, originated from SiO 2 catalytically decomposed by Fe droplets. In the absence of a Cu foil covering an Fe-coated SiO 2 /Al 2 O 3 template, the catalytic activity of Fe droplets was significantly suppressed because of the encapsulation of Fe droplets by a 2-nm-thin-Fe 3 O 4 layer. Furthermore, a part of the Fe film on SiO 2 /Al 2 O 3 without a Cu foil turned into nanodroplets and assisted the formation of SiO 2 nanowires. These results reveal that a Cu foil made an intriguing role in preventing Fe from being encapsulated by Fe 3 O 4 , so the catalytic role of Fe droplets was not terminated until SiO 2 was fully decomposed. Our experimental results provided insights into better understanding of these intriguing behaviors of Fe and Cu on SiO 2 at high temperature and at atmospheric pressure.