The electronic transport properties of monolayer graphene have been studied before and after the deposition of a dilute coating of tungsten adatoms on the surface. For coverages up to 2.5\% of a monolayer, we find tungsten adatoms simultaneously donate electrons to graphene and reduce the carrier mobility, impacting the zero- and finite-field transport properties. Two independent transport analyses suggest the adatoms lie nearly 1 nm above the surface. The presence of adatoms is also seen to impact the low field magnetoresistance, altering the signatures of weak localization.Comment: 19 pages, 4 figures; fixed figure sizes and caption

The electronic transport of monolayer graphene devices is studied before and after in situ deposition of a sub‐monolayer coating of osmium adatoms. Unexpectedly, and unlike all other metallic adatoms studied to date, osmium adatoms shift the charge neutrality point to more positive gate voltages. This indicates that osmium adatoms act as electron acceptors and thus leave the graphene hole‐doped. Analysis of transport data suggest that Os adatoms behave as charged impurity scatterers, albeit with a surprisingly low charge‐doping efficiency. The charge neutrality point of graphene is found to vary non‐monotonically with gate voltage as the sample is warmed to room temperature, suggesting that osmium diffuses on the surface but is not completely removed.

through a combination of single crystal growth, experiments involving in situ deposition of surface adatoms, and complimentary modeling, we examine the electronic transport properties of lithiumdecorated Zrte 5 thin films. We observe that the surface states in ZrTe 5 are robust against Li adsorption. Both the surface electron density and the associated Berry phase are remarkably robust to adsorption of Li atoms. fitting to the Hall conductivity data reveals that there exist two types of bulk carriers: those for which the carrier density is insensitive to Li adsorption, and those whose density decreases during initial Li depositions and then saturates with further Li adsorption. We propose this dependence is due to the gating effect of a Li-adsorption-generated dipole layer at the ZrTe 5 surface. Surface adsorption has long been a powerful method to tailor the electronic, optical, magnetic, and chemical properties of many material systems. With the advent of research on graphene 1,2 , a two-dimensional (2D) Dirac material exposed directly to environment 3 , studies have been carried out in examining how adsorption of adatoms can modify its electronic transport properties 4-9. Indeed, due to a strong coupling between the adatoms and the 2D electron system, it has been shown that adsorption can induce distinctive properties by modifying the spin, orbital, and charge degrees of freedom. Dirac semimetals, which are a 3D analog of graphene, were theoretically predicted 10,11 and experimentally confirmed 12 in the last decade. An exciting feature of these materials is the topologically protected surface states. As with graphene, these surface states are exposed to the environment. Thus, surface adsorption may strongly modify the topological surface states in these semimetals. Several theoretical studies have been carried out to address this question, for example, a charge transfer mechanism in surface adsorption in discussed in ref. 13,14 describes the robustness of the surface states against surface adatoms. Few experiments have explored the adsorption of adatoms on three-dimensional Dirac semimetals, though a study of molecular deposition on Na 3 Bi finds an efficient hole-doping mechanism 15. Understanding such surface interactions is important, as it directly relates to incorporating these materials into topological electronics.

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