  We employ low-frequency Raman spectroscopy to study the nearly commensurate
(NC) to commensurate (C) charge density wave (CDW) transition in 1T-TaS2
ultrathin flakes protected from oxidation. We identify new modes originating
from C phase CDW phonons that are distinct from those seen in bulk 1T-TaS2. We
attribute these to CDW modes from the surface layers. By monitoring individual
modes with temperature, we find that surfaces undergo a separate,
low-hysteresis NC-C phase transition that is decoupled from the transition in
the bulk layers. This indicates the activation of a secondary phase nucleation
process in the limit of weak interlayer interaction, which can be understood
from energy considerations.
