Spectroscopic Ellipsometry of CVD Graphene

Hydrocarbon-based CVD on metallic substrates provides a means of scalable fabrication of graphene thin films. CVD graphene is known to have grain boundaries which impact carrier mobility and optical response. Here, we use spectroscopic Ellipsometry (SE) to characterize the complex refractive index of Chemical Vapor Deposition (CVD) graphene grown on copper (Cu) foils and transferred to glass substrates. Two ellipsometers, with respective wavelength ranges extending into the ultra-violet (UV) and infrared (IR), have been used to characterize the CVD graphene optical constants. Our data follows the same relation to the fine structure constant observed in IR region by Heinz, et. al. We also observe the exciton dominated absorption peak at ~4.5 eV previously reported for exfoliated graphene by . The optical constants of CVD graphene show some differences to published values for exfoliated graphene. A Monte Carlo fit analysis is subsequently used for uncertainty determination. Wafer maps of 300 mm silicon wafers show the capability of ellipsometry to provide process control during manufacturing.