Morphology Control of Graphene by LPCVD
We present a comprehensive study of the parameter for graphene growth by low pressure chemical vapor deposition on Cu foil. The growth of graphene was investigated in various conditions, changing the gas pressures, gas ratio, growth temperature and growth time. The synthesized graphene were characterized using Raman spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). By varying the growth time it can be concluded that the domain size increases when the growth time increases. The absence of 2D band in this section suggest that the produced graphene-like films are not monolayer and graphite can be formed in this growth conditions. The FESEM images demonstrate that increasing growth temperature while holding other parameters constant yields in larger domains which may be due to a faster growth at the higher temperature. The Raman spectra also showed the recovery of the 2D peak by increasing the growth temperature, indicating the crystallization of the damaged graphene layer. Hence the quality of grown graphene-like films is highly correlated to the process temperature. We show that the methane-to-hydrogen ratio is critical parameters that affect the structural perfection of graphene like domains. The Raman studies denote graphene like carbon nature due to the appearance of significant G and 2D peaks. Also the 2D peak intensity increases by increasing the H2 concentration in gas mixture, indicating a low graphene layers. The resulting domain size and the nucleation density are maximum at maximum value of H2 concentration. We can conclude that by controlling the growth parameters, the morphology and structure of graphene can be changed. We suggest that graphene can be used for fusion reactor first wall due to its unique physical and chemical properties. Our results provide important guidance toward the synthesis of high quality and uniform graphene films.