Characteristics of graphene grown through low power capacitive coupled radio frequency plasma enhanced chemical vapor deposition

We study the characteristics of graphene grown through low power capacitive coupled radio frequency plasma enhanced chemical vapor deposition (PECVD) and explore its application. Fully-covered, mostly single-layered, and highly defective graphene films were grown on Cu substrates through plasma composed of various argon/methane/hydrogen gas ratio with low RF power within a minute under a moderate substrate temperature at 850°C. The structural, chemical, and electrical properties of the graphene films were measured through Raman spectroscopy, X-ray photoelectron spectroscopy, and Hall measurement, respectively. The Raman signatures were strongly affected by the argon/hydrogen flow rates and the subsequent thermal annealing, and is strongly correlated to carrier mobility of the film. Through analysis of the defect related Raman bands within the theoretical framework of activated defect model, it is concluded that the defects found in the graphene films are originated from ion bombardment during the growth processes. The vacancy defects on the graphene film provides adsorption sites for gaseous molecules and induces changes of charge transfer in the graphene film. The response of the graphene-based sensor fabricated with the PECVD grown graphene is 6% under 100 ppb of NO₂, which can be a candidate of potential NO₂ gas sensing material in the future.