Room-Temperature Patterning of Nanoscale MoS₂ under an Electron Beam

Molybdenum disulfide (MoS₂) is traditionally grown at a high temperature and subsequently patterned to study its electronic properties or make devices. This method imposes severe limitations on the shape and size of MoS₂ crystals that can be patterned precisely at required positions. Here, we describe a method of direct nanoscale patterning of MoS₂ at room temperature by exposing a molybdenum thiocubane single-source precursor to a beam of electrons. Molybdenum thiocubanes with various alkylxanthate moieties [Mo₄S₄(ROCS₂)₆, where R = alkyl] were prepared using a "self-assembly" approach. Micro-Raman and micro-FTIR spectroscopic studies suggest that exposure to a relatively smaller dose of electrons results in the breakdown of xanthate moieties, leading to the formation of MoS₂. High-resolution transmission electron micrographs suggest that the growth of MoS₂ most likely happens along (100) planes. An electron-beam-induced chemical transformation of a molybdenum thiocubane resist was exploited to fabricate sub-10 nm MoS₂ lines and dense dots as small as 13 nm with a pitch of 33 nm. Since this technique does not require the liftoff and etching steps, patterning of MoS₂ with interesting shapes, sizes, and thicknesses potentially leading to tunable band gap is possible.