Nanoribbons: Mechanical Exfoliation, Thickness-Dependent Raman Spectroscopy and Electronic Properties

Quasi-one-dimensional (quasi-1D) materials enjoy growing interest due to their unusual physical properties and promise for miniature electronic devices. We investigated the micromechanical exfoliation of representative quasi-1D crystals, TiS₃ whiskers, and demonstrate that they typically split into narrow nanoribbons with very smooth edges and clear signatures of 1D TiS₃ chains. Theoretical calculations show that the energies required for breaking weak interactions between the 2D layers and between 1D chains within the layers are comparable, and in turn are considerably lower than those required for breaking the covalent bonds within the chains. We systematically studied the exfoliated TiS₃ crystals by Raman spectroscopy and identified the Raman peaks whose spectral positions were most dependent on the crystals' thickness. Finally, we fabricated TiS₃-based electronic devices and tested their transport properties. The conclusions established in this study for the exfoliated TiS₃ crystals can be extended to a variety of transition metal trichalcogenide materials as well as other quasi-1D crystals. The possibility of exfoliation of TiS₃ into few-nm wide crystals with smooth edges is important for realization of miniature device channels with reduced edge scattering.