Characterization of low temperature graphene synthesis in inductively coupled plasma chemical vapor deposition process with optical emission spectroscopy

Low-temperature graphene was synthesized at 400 °C with inductively coupled plasma chemical vapor deposition (PECVD) process. The effects of plasma power and flow rate of various carbon containing precursors and hydrogen on graphene properties were investigated with optical emission spectroscopy (OES). Various radicals monitored by OES were correlated with graphene film properties such as sheet resistance, I_D/I_G ratio of Raman spectra and transparency. C₂H₂ was used as a main precursor and the increase of plasma power enhanced intensity of carbon (C₂) radical OES intensity in plasma, reduced sheet resistance and increased transparency of graphene films. The reduced flow rate of C₂H₂ decreased sheet resistance and increased transparency of graphene films in the range of this study. H₂ addition was found to increase sheet resistance, transparency and attributed to reduction of graphene grain and etching graphene layers. OES analysis showed that C₂ radicals contribute to graphite networking and sheet resistance reduction. TEM and AFM were applied to provide credible information that graphene had been successfully grown at low temperature.