We investigate the adsorption sites of $3d$ transition metal (TM) adatoms bymeans of low-temperature scanning tunneling microscopy and spectroscopy. Co andNi adatoms were adsorbed on two types of graphene on SiC(0001), i.e. pristineepitaxial monolayer graphene (MLG) and quasi-free-standing monolayer graphene(QFMLG). In the case of QFMLG, two stable adsorption sites are identified,while in the case of MLG, only one adsorption site is observed. Ourexperimental results reveal the decoupling efficiency as a crucial parameterfor determining the adsorption site as well as the electronic properties of$3d$ transition metal atoms on graphene. Furthermore, we show that Co atomsadsorbed on QFMLG are strong scattering potentials for Dirac fermions and causeintervalley scattering in their vicinity.
展开▼
