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It is well known that the CVD method is currently the most effective method for preparing a high-quality single-layer large-area graphene film, but the current process requires a high temperature of 1000 ° C or higher, the cost is high, and the process is complicated. Recently, a team of researchers from Japan and Taiwan created a new CVD method that uses a dilute methane vapor source and a molten gallium catalyst to grow graphene at temperatures as low as 50 °C. The results of the study were published in the journal "Scientific reports" under the recent "Nature". Reducing the CVD synthesis temperature of graphene can excellently integrate graphene into various applications, such as direct integration of CVD-grown graphene into electronic devices. The team explained that in silicon-based electronics, the upper limit temperature at which components can withstand graphene integration is about 400 °C. Plastic semiconductor devices have even lower thresholds and can only withstand temperatures up to 100 °C during graphene growth. Under conventional CVD techniques, graphene growth occurs around 1000 ° C and is not suitable for direct integration into electronic devices. 
The new method of carbon source decomposition and graphene growth can break this limitation. The team used molten gallium as a catalyst to grow CVD graphene on sapphire and polycarbonate substrates with the help of a dilute methane atmosphere. Can be reduced to about 50 °C. Gallium is selected as a catalyst because it is a catalyst which has proven to be effective in the recent graphene growth method, and can be easily removed by a gas jet after synthesizing graphene. The carbon source is a mixture of air and nitrogen and argon mixed to dilute to 5% methane gas. 
Characterization of graphene The researchers examined the quality of graphene grown using Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The characterization results show that the new CVD process is capable of growing high quality graphene at near room temperature (relatively), and graphene is grown on polycarbonate substrates and sapphire substrates at 50 ° C and 100 ° C, respectively. Low temperature synthesis can be achieved by attaching carbon to the edges of the pre-grown graphene nucleus without damaging the substrate or surrounding components. The pre-existing nuclei themselves are prepared by conventional CVD processes or by special nuclear transfer techniques using mixtures 12C and 13C at low temperatures. The presence of a molten gallium catalyst promotes methane absorption at lower temperatures, resulting in a very low final reaction barrier below 300 ° C and 0.16 eV. Studies have also found that the molten state of gallium is sufficient to flow to promote increased transport and growth of carbon atoms. The study found that the rapid growth kinetics associated with lower reaction barriers and low-temperature nuclear transfer processes promoted the growth of graphene down to 50 ° C and was the result of a competitive pathway, namely the decomposition of methane on the gallium surface; Liquid gallium adsorbs methane, which is then deposited in gallium. The study also found that these two pathways are advantageous at high and low temperatures, respectively, and explain the reasons for the weak temperature dependence and low reaction barrier in the process. The methane absorption pathway is also considered to be a unique feature of molten gallium because it is found to be ineffective when other metals are used, including common graphene catalysts such as copper and nickel. This research is a major advancement in low temperature graphene synthesis technology. For the first time, researchers have grown graphene directly onto plastic substrates. Anyone in the graphene field will understand the potential impact of low temperature synthesis methods and can be used to integrate graphene into a variety of electronic devices in the future.
Recently, researchers from Japan and Taiwan have created a new CVD method that uses a dilute methane vapor source and a molten gallium catalyst to grow graphene at temperatures as low as 50 °C. This research is a major advancement in low temperature graphene synthesis technology. For the first time, researchers have directly grown graphene onto plastic substrates, and in the future, graphene can be integrated into various electronic devices.