Monolayer Molybdenum Disulfide Nanoribbons with High Optical Anisotropy

Abstract

Two-dimensional Molybdenum Disulfide (MoS2) has shown promising prospects for the next generation electronics and optoelectronics devices. The monolayer MoS2 can be patterned into quasi-one-dimensional anisotropic MoS2 nanoribbons (MNRs), in which theoretical calculations have predicted novel properties. However, little work has been carried out in the experimental exploration of MNRs with a width of less than 20 nm where the geometrical confinement can lead to interesting phenomenon. Here, we prepared MNRs with width between 5 nm to 15 nm by direct helium ion beam milling. High optical anisotropy of these MNRs is revealed by the systematic study of optical contrast and Raman spectroscopy. The Raman modes in MNRs show strong polarization dependence. Besides that the E' and A'1 peaks are broadened by the phonon-confinement effect, the modes corresponding to singularities of vibrational density of states are activated by edges. The peculiar polarization behavior of Raman modes can be explained by the anisotropy of light absorption in MNRs, which is evidenced by the polarized optical contrast. The study opens the possibility to explore quasione-dimensional materials with high optical anisotropy from isotropic 2D family of transition metal dichalcogenides

Tungsten Diselenide Patterning and Nanoribbon Formation by Gas‐Assisted Focused‐Helium‐Ion‐Beam‐Induced Etching

“…Recently, Wu et al have demonstrated that MoS 2 nanoribbons demonstrate highly anisotropic optical behavior. The optical anisotropy and enhanced intensity of the Raman modes are attributed to anisotropy in optical absorption depending upon NR orientation and NR edges, which breaks up the translational symmetry of the crystal and relax selection rules, respectively.…”

“…The HIM has shown potential to pattern and selectively introduce defects with high resolution into 2D materials such as MoS 2 , MoSe 2 , WSe 2 , and graphene . Of particular interest, transition metal dichalcogenide (TMD) nanoribbons have been theorized to exhibit unique properties depending upon edge termination .…”

Symmetry‐Reduction Enhanced Polarization‐Sensitive Photodetection in Core–Shell SbI3/Sb2O3 van der Waals Heterostructure

“…Symmetry‐reduction as a method of disordering atoms to change the density of states in a certain direction by heterostructure enhances the dichroic ratio. Therefore, symmetry‐reduction as a valid method of enhancing structural anisotropy can numerously enrich the family of in‐plane anisotropy semiconductors and has extensively utilized in polarization‐sensitive photodetection …”

Scalable integration of periodically aligned 2D-MoS2 nanoribbon array

“…Besides, the active area patterned by these conventional methods is insufficient to be practically employed. To date, several alternative nanofabrication techniques have been reported, which relies on the following four methods: (1) selective growth on the patterned templates, 12,13 (2) reactive ion etching using patterned masks, 14,15 (3) direct removal by scanning lasers or ions, 16,17 and (4) peeling, transfer, and filling methods by controlling a surface adhesion energy. [18][19][20] In method (1), the prepared Mo nanowires were converted to MoS 2 nanowires through pyrolysis in H 2 S ambient; however, these MoS 2 nanowires exhibited unstable electrical properties owing to a Y.…”

“…4(c)]. The absolute PL intensity was slightly weakened in the MNR due to the reduced active area and the open edges, 17,26 but the two exciton peaks were clearly observed at 1.83 eV and 1.97 eV related to the K-point transition in the Brillouin zone. 1 By contrast, the reference MNR with residues or the photoresist-coated MoS 2 displayed broad peaks with fluctuating backgrounds, implying that application devices based on such platforms will produce unstable characteristics.…”