  A distinctive feature of single layer graphene is the linearly dispersive
energy bands, which in case of multilayer graphene become parabolic. Other than
the quantum Hall effect, this distinction has been hard to capture in electron
transport. Carrier mobility of graphene has been scrutinized, but many parallel
scattering mechanisms often obscure its sensitivity to band structure. The
flicker noise in graphene depends explicitly on its ability to screen local
potential fluctuations. Here we show that the flicker noise is a sensitive
probe to the band structure of graphene that vary differently with the carrier
density for the linear and parabolic bands. Using devices of different genre,
we find this difference to be robust against disorder in the presence or
absence of substrate. Our results reveal the microscopic mechanism of noise in
Graphene Field Effect Transistors (GraFET), and outline a simple portable
method to separate the single from multi layered devices.
