Interaction of graphene with Au _n clusters: a first-principles study

Abstract

The interaction between Aun (n=1-6) clusters and graphene is studied using first-principles simulations, based on density functional theory. The computed binding energy between Aun and graphene depends on the number of atoms in the cluster and lies between -0.6 eV and -1.7 eV, suggesting (weak) chemisorption of the clusters on graphene, rather than physisorption. Overall, the electronic properties, spin-orbit interaction and spin texture, as well as the transport properties of graphene strongly depend on the precise size of the Aun clusters. Doping of graphene is predicted for clusters with an odd number of Au atoms, due to overlap between Au s and carbon pz states close to the Fermi level. On the other hand, there is no charge transfer between even size Au clusters and graphene, but a gap is formed at the Dirac cone, due to the breaking of the pseudospin inversion symmetry of graphene’s lattice. The adsorbed Aun clusters induce spin-orbit interactions as well as spin and pseudospin interactions in graphene, as indicated by the splitting of the electronic band structure. A hedgehog spin texture is also predicted for adsorbed clusters with an even number of Au atoms. Ballistic transport simulations are performed to study the influence of the adsorbed clusters on graphene’s electronic transport properties. The influence of the cluster on the electron transmission across the structure depends on the mixing of the valence orbitals in the transport energy window. In the specific case of the Au3/graphene system, the adsorbed clusters reduce the transmission and the conductance of graphene. The Au3 clusters act as “scattering centres” for charge carriers, in agreement with recent experimental studies.

Tuning the spin texture of graphene with size-specific Cu n clusters: a first-principles study

“…Consequently, the size of the cluster plays a significant role in favouring certain component of the spins. In comparison with our earlier work on Au n /graphene systems [23], the induced splitting in Cu n /graphene is smaller but chiral spin texture was not observed for Au 4 /graphene (since the in plane distortion in Au 4 /graphene is twice as large as in Cu 4 /graphene). This provides the opportunity to engineer Cu n cluster size dependent spin polarizers, as discussed below.…”

“…Note that the geometries of the isolated Cu n clusters are also similar to the Au n clusters, reported in our previous work [23], since both elements share a similar electronic configuration. However, compared to the Au n /graphene systems, where the Au n clusters are weakly chemisorbed (−0.6 to −1.7 eV), the lower binding energies between Cu n and graphene rather suggest a physisorption process.…”

“…However, to realize innovative manipulation and generation of spin currents, its spin-orbit coupling (SOC) needs to be amplified by orders of magnitude. Several research efforts have been made to induce SOC by proximity, which include forming graphene-vdW heterostructures [18,19] and the adsorption of adatoms like hydrogen [20], fluorine [21] and heavy metals Os [13], Au [22,23] and In [14]. In all these cases, SOC induced band splitting is in the range of few meV.…”

Stability and Electronic Structure of Nitrogen-Doped Graphene-Supported Cun (n = 1–5) Clusters in Vacuum and under Electrochemical Conditions: Toward Sensor and Catalyst Design

“…It is worth noting that the interaction energies between the substrates and the metal clusters are roughly twice as high with nitrogendoped graphene compared to pristine graphene or graphene with a vacancy. 52 Furthermore, on pristine and on single vacancy defected graphene, the Cu 3 and Cu 5 were found to be the most stable, respectively. 52 3.2.…”

“…We also study the electronic structures using advanced symmetry considerations. Murugesan et al 52 studied Cu n (n = 1−5) clusters deposited on free and single vacancydefected graphene surface using DFT computations. They focused on possible applications in the field of spintronics.…”