Applied Physics Letters
Modification of electronic band structure in mL + nL (m = 1, 2; n = 1–5) free-stacking graphene
Applied Physics Letters · 109, 153111 (2016)
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Introduction
Raman spectra track the 2D band when graphene sheets of different layer counts are stacked. When one constituent is a monolayer, the band shifts to higher frequency, with a larger shift as the other constituent becomes thicker.
A closer reading
Comparing the stack with the spectra of its constituent sheets first separates superposition from an additional shift. The inferred change in monolayer Fermi velocity is the model-based interpretation of that shift, not a direct velocity measurement.