(Invited) Interesting 1-D and 2-D Phases of MoS2

Abstract

Tailoring the dimension of nanomaterials to achieve precise tuning of optical, electronic and catalytic properties have been the major goals of researchers for decades. Two dimensional metal chalcogenides of the MX2 (M=Mo, W and Ti, X= Se, Te) family represent the ultimate control of material dimension in the vertical direction, and exhbits unique quantum confined optoelectronic properties. At the 1-D level, MoS2 quantum wires display quasi one-dimensional metallic state and novel ferromagnetic behavior that is tunable by its width and edge configurations. Unlike graphene nanoribbons which have been successfully synthesized using bottom–up molecular techniques, there are scant reports on the growth of MoS2 nanoribbons. Herein, we report two novel phases of sub-stochiometric MoS2 (MoSx) grown on Au (111) and Cu (111), respectively. We performed the templated growth of well-aligned, sub-stoichiometric MoSx molecular wire on Au(111) vicinal surface. Interestingly, we observed the dynamic assembly of MoSx molecular wires and its phase transition into stoichiometric MoS2 nanoribbon. On Cu (111) surfaces, we studied the growth of a novel MoSx 2-D phase which shows catalytic activities for the oligomerization of small molecules on its basal planes. Due to the in-plane rotational freedom and greater diversity of bonding arrangements in MoS2, a plethoras of different polytypes may be possible when the structural assembly is mediated by metal substrate. Thus a whole new class of alternative 2D structures, uniquely different to the classical chalcogenides in terms of electronic and physical properties, may be possible.