Better on MoS₂

Phys. Rev. Lett. 113, 156804 (2014)

The electronic properties of pristine graphene, such as its high charge-carrier mobility, are what make it a promising material for the next generation of information-processing devices. However, interactions with the substrate on which graphene sheets are grown, or transferred to, usually have detrimental effects on the electronic properties, by, for example, reducing the carrier mobility or mean free path. So far, hexagonal boron nitride has been considered the most suitable insulating substrate for preserving the intrinsic properties of graphene in devices. On the other hand, the small mismatch in the lattice constants of the two materials gives rise to a moiré potential, which influences the charge carriers in graphene. Chih-Pin Lu and colleagues at Rutgers University, National Taiwan University and the National Institute for Materials Science in Tsukuba now report that MoS₂ could in fact be a better choice of substrate.

MoS₂ is atomically flat, has a large lattice mismatch with graphene and is a semiconductor. The researchers studied the properties of graphene on exfoliated sheets of MoS₂ by scanning tunnelling and Landau-level spectroscopy, and found that the MoS₂ substrate allows the intrinsic electronic properties of graphene to be retained, without inducing modifications in its band structure. The researchers also showed that the screening of charges in the graphene layer could be tuned by changing the Fermi level of the MoS₂ via voltage gating, resulting in longer mean free paths.