Activation of the carbon buffer layer on 4H- and 6H-SiC substrates using elements with high magnetic moments may lead to novel graphene/SiC-based spintronic devices. In this work, we use a variety of surface analysis techniques to explore the intercalation of Er underneath the buffer layer showing evidence for the associated formation of quasi-free-standing graphene (QFSG). A combined analysis of low energy electron diffraction (LEED), atomic force microscopy (AFM), X-ray and ultraviolet photoemission spectroscopy (XPS and UPS), and metastable de-excitation spectroscopy (MDS) data reveals that annealing at temperatures up to 1073 K leads to deposited Er clustering at the surface. The data suggest that intercalation of Er occurs at 1273 K leading to the breaking of back-bonds between the carbon buffer layer and the underlying SiC substrate and the formation of QFSG. Further annealing at 1473 K does not lead to the desorption of Er atoms but does result in further graphitization of the surface.