title: Intrinsic Phonon Bands in High-Quality Monolayer T' Molybdenum Ditelluride.
abstract: The topologically nontrivial and chemically functional distorted octahedral (T') transition-metal dichalcogenides (TMDCs) are a type of layered semimetal that has attracted significant recent attention. However, the properties of monolayer (1L) T'-TMDC, a fundamental unit of the system, are still largely unknown due to rapid sample degradation in air. Here we report that well-protected 1L CVD T'-MoTe2exhibits sharp and robust intrinsic Raman bands, with intensities about 1 order of magnitude stronger than those from bulk T'-MoTe2. The high-quality samples enabled us to reveal the set of all nine even-parity zone-center optical phonons, providing reliable fingerprints for the previously elusive crystal. By performing light polarization and crystal orientation resolved scattering analysis, we can effectively distinguish the intrinsic modes from Te-metalloid-like modes A (∼122 cm-1) and B (∼141 cm-1), which are related to the sample degradation. Our studies offer a powerful nondestructive method for assessing sample quality and for monitoring sample degradation in situ, representing a solid advance in understanding the fundamental properties of 1L-T'-TMDCs.
authors.affiliation: Department of Physics, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Shao-Yu
authors.initials: SY
authors.lastname: Chen
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Carl H
authors.initials: CH
authors.lastname: Naylor
authors.affiliation: Department of Physics, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Goldstein
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: A T Charlie
authors.initials: AT
authors.lastname: Johnson
authors.affiliation: Department of Physics, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Jun
authors.identifier: 0000-0003-3861-4633
authors.initials: J
authors.lastname: Yan
keywords: Raman scattering; anisotropy; crystal quality; monolayer T′ molybdenum ditelluride; topological insulator; transition-metal dichalcogenide