Intrinsic Phonon Bands in High-Quality Monolayer T' Molybdenum Ditelluride

TL;DR

This study reveals intrinsic phonon modes in high-quality monolayer T'-MoTe2 using Raman spectroscopy, providing fundamental insights into its crystal structure and a method to assess sample quality non-destructively.

Contribution

The paper reports the first identification of all nine intrinsic zone-center optical phonons in monolayer T'-MoTe2, enabled by high-quality protected samples and polarization-resolved analysis.

Findings

Sharp intrinsic Raman bands observed in monolayer T'-MoTe2

All nine even-parity zone-center optical phonons identified

Method developed to distinguish intrinsic modes from degradation-related modes

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, is still largely unknown due to rapid sample degradation in air. Here we report that well-protected 1L CVD T'-MoTe2 exhibits sharp and robust intrinsic Raman bands, with intensities about one 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 non-destructive 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.