Covalent bonds formed in MoS2-C60/Ferrocene heterostructure under high pressure

Constructing mixed dimensional heterostructure can create the possibility for obtaining new structures and properties by combining the advantages of both materials. Further introducing external means to control intermolecular/atomic distance and configuration may affect the bonding form, band structure, and interfacial interaction, which brings more novel function materials. In this work, high pressure Raman studies and theoretical research have been carried out on monolayer MoS2-C60/Ferrocene (C60/Fc) heterostructures to explore the possible phase transitions and interfacial bonding changes. We found that the interaction between C60/Fc and MoS2 molecules gradually enhanced as pressure increased, accompanying by a large wavenumber splitting of Ag (2) mode and the appearance of new peaks around 700-800 cm-1. These phenomena indicated that not only the polymeric structure was formed between C60 molecules, but some C atoms connected with adjacent S atoms at the interface to form covalent bonds with the help of pressure. The theoretical studies further indicated the possible bonds formation between C and S atoms. Surprisingly, the covalent bonds can still be observed at lower pressure when pressure decompressed, while the long-range ordered polymer structure between C60s can be maintained at atmospheric pressure.