  Results of room temperature Raman scattering studies of ultrathin graphitic
films supported on Si (111)/SiO2 substrates are reported. The results are
significantly different from those known for graphite. Spectra were collected
using 514 nm radiation on films containing from n=1 to 20 graphene layers, as
determined by atomic force microscopy. Both the 1st and 2nd order Raman spectra
show unique signatures of the number of layers in the film. The nGL film analog
of the Raman G-band in graphite exhibits a Lorentzian lineshape whose center
frequency shifts linearly relative to graphite as ~1/n (for n=1 G-band
frequency ~1588 cm-1). Three weak bands, identified with disorder-induced 1st
order scattering, are observed at ~ 1350, 1450 and 1500 cm-1. The 1500 cm-1
band is weak but relatively sharp and exhibits an interesting n-dependence. In
general, the intensity of these D-bands decreases dramatically with increasing
n. Three 2nd order bands are also observed (~2450, ~2700 and 3248 cm-1). They
are analogs to those observed in graphite. However, the ~2700 cm-1 band
exhibits an interesting and dramatic change of shape with n. Interestingly, for
n<5 this 2nd order band is more intense than the G-band.
