Quasi-2D Cu2 S crystals on graphene: in-situ growth and ab-initio calculations.

Two-dimensional crystals of beta-copper sulfide are synthesized in an in-situ electron microscopy experiment. Copper crystals are deposited on an amorphous carbon film containing sulfur. The carbon film graphitizes upon heating and electron irradiation and allows the reaction of Cu and S towards two-dimensional Cu(2) S crystals. These are energetically favourable and bonded via van der Waals interactions to the graphitic substrate.