Electronic transport in graphene decorated with adatoms or nanoparticles*

There is much interest in inducing a spin-orbit coupling into monolayer graphene in order to engineer the Kane-Mele Hamiltonian and thereby enable observation of the quantum spin Hall effect in graphene. Numerous adatoms have been studied toward this end. Here, we present measurements of monolayer graphene Hall bars with dilute coatings of either osmium adatoms or Bi_²Te_³ nanoparticles (NPs). With osmium adatoms, we find an unusual hole doping to occur, whereas most metals show electron doping. Nanoparticles of Bi_²Te_³ have recently been reported to yield possibly quantized transport [1]. We use high quality NPs, monodispersed with diameters of ~15 nm. Transport is studied after depositing the nanoparticles, and again after an argon anneal to remove the polyvinylidene fluoride coating on the NPs. In this case a small electron doping response is observed. Further measurements on higher density coatings of both osmium adatoms and Bi_²Te_³ nanoparticles will be discussed.
[1] K. Hatsuda, H. Mine, T. Nakamura, J. Li, R. Wu, S. Katsumoto, J. Haruyama, arXiv:1806.07027, (2018)