Monitoring and analyses of substrate surface in first stages of graphene growth in plasma-enhanced chemical vapor deposition

In situ ellipsometry was carried out as well as ex situ measurements by scanning electron microscopy and Raman spectroscopy for the analyses of substrate surface in the first stage of graphene growth in plasma-enhanced chemical vapor deposition. Evolutions of the ellipsometric parameters Ψ and Δ were precisely measured during the growth of graphene with the sensitivity far less than 1 nm in film thickness. By the fitting of the experimentally obtained trajectory of ellipsometric parameters on the Ψ-Δ coordinate plane to that of the calculated ones, we confirmed that the graphite volume fraction decreased with growth after a dense graphite material initially formed. This suggests that carbon nanowalls grew on a thin graphitic layer.