  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.
