Co6Se8(PEt3)6 superatoms as tunable chemical dopants for two-dimensional semiconductors

Electronic, optoelectronic, and other functionalities of semiconductors are controlled by the nature and density of carriers, and the location of the Fermi energy. Developing strategies to tune these parameters holds the key to precise control over semiconductors properties. We propose that ligand exchange on superatoms can offer a systematic strategy to vary these properties. We demonstrate this by considering a WSe2 surface doped with ligated metal chalcogenide Co6Se8(PEt3)6 clusters. These superatoms are characterized by valence quantum states that can readily donate multiple electrons. We find that the WSe2 support binds more strongly to the Co6Se8 cluster than the PEt3 ligand, so ligand exchange between the phosphine ligand and the WSe2 support is energetically favorable. The metal chalcogenide superatoms serves as a donor that may transform the WSe2 p-type film into an n-type semiconductor. The theoretical findings complement recent experiments where WSe2 films with supported Co6Se8(PEt3)6 are indeed found to undergo a change in behavior from p- to n-type. We further show that by replacing the PEt3 ligands by CO ligands, one can control the electronic character of the surface and deposited species.