Year: 2021
Type: article
Abstract: Janus transition metal dichalcogenides (TMDs) lose the horizontal mirror symmetry of ordinary TMDs, leading to the emergence of additional features, such as native piezoelectricity, Rashba effect, and enhanced catalytic activity. While Raman spectroscopy is an essential nondestructive, phase- and composition-sensitive tool to monitor the synthesis of materials, a comprehensive study of the Raman spectrum of Janus monolayers is still missing. Here, we discuss the Raman spectra of WSSe and MoSSe measured at room and cryogenic temperatures, near and off resonance. By combining polarization-resolved Raman data with calculations of the phonon dispersion and using symmetry considerations, we identify the four first-order Raman modes and higher-order two-phonon modes. Moreover, we observe defect-activated phonon processes, which provide a route toward a quantitative assessment of the defect concentration and, thus, the crystal quality of the materials. Our work establishes a solid background for future research on material synthesis, study, and application of Janus TMD monolayers.
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Funders: National Science Foundation, U.S. Department of Energy, Alexander von Humboldt-Stiftung, European Commission, Deutsche Forschungsgemeinschaft, Bayerische Akademie der Wissenschaften, International Max Planck Research School for Advanced Methods in Process and Systems Engineering, Munich Center for Quantum Science and Technology, International Max Planck Research School for Quantum Science and Technology, Horizon 2020, Division of Materials Research, Division of Civil, Mechanical and Manufacturing Innovation, International Graduate School of Science and Engineering
Awards: G1053943915, G1768993395, G2133534608, G258225891, G2584691830, G2657181000, G2920044675, G3386364313, CAREER: Point Defects in Two-dimensional Material Systems: Fundamentals and New Perspectives, G434337789, G5768859344, G5884696758, G6126221430, Scalable Two-Dimensional Quantum Integrated Photonics, EAGER: The Fundamentals of Exotic Exciton Complexes in 2D Janus Semiconductors, THE SYNTHESIS 2D JANUS VDW CRYSTALS AND NOVEL QUANTUM PHENOMENA ARISING FROM MIRROR-SYMMETRY BREAKING, G8707856532, G8939273476, G967591279, Wafer-Scale Manufacturing of Two-Dimensional Anisotropic Nanomaterials by Chemical Vapor Deposition
OpenAlex ID: W3036500810