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Room-Temperature Patterning of Nanoscale MoS2 under an Electron Beam

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journal contribution
posted on 25.03.2020, 15:05 by Mohammad S. M. Saifullah, Mohamed Asbahi, Maryam Binti-Kamran Kiyani, Sing Shy Liow, Surani Bin Dolmanan, Anna Marie Yong, Esther A. H. Ong, Asadullah Ibn Saifullah, Hui Ru Tan, Neeraj Dwivedi, Tanmay Dutta, Ramakrishnan Ganesan, Suresh Valiyaveettil, Karen S. L. Chong, Sudhiranjan Tripathy
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.