Strain engineering, efficient excitonic photoluminescence, and exciton funnelling in unmodified MoS2 nanosheets.

We established locally varying strain fields in unmodified MoS2 nanosheets. The approach relies on dry release in place of multilayer MoS2 on textured Si substrates. By this process we demonstrated intense photoluminescence, a ∼70 meV decrease of the transition energy, and exciton funneling in ∼4 nm-thick MoS2 films.

Passivation of Germanium by Graphene.

The oxidation of Ge covered with graphene that is either grown on or transferred to the surface is investigated by X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. Graphene properly grown by chemical vapor deposition on Ge(100), (111), or (110) effectively inhibits room-temperature oxidation of the surface. When graphene is transferred to the Ge surface, oxidation is reduced relative to that on uncovered Ge but has the same power law dependence. We conclude that access to the graphene/Ge interface must occur via defects in the graphene. The excellent passivation provided by graphene grown on Ge should enhance applications of Ge in the electronic-device industry.