Raman Scattering from High-Frequency Phonons in Supported n-Graphene Layer Films

A Gupta, G Chen, P Joshi, S Tadigadapa, Eklund - Nano letters, 2006 - ACS Publications
A Gupta, G Chen, P Joshi, S Tadigadapa, Eklund
Nano letters, 2006ACS Publications
Results of room-temperature Raman scattering studies of ultrathin graphitic films supported
on Si (100)/SiO2 substrates are reported. The results are significantly different from those
known for graphite. Spectra were collected using 514.5 nm radiation on films containing
from n= 1 to 20 graphene layers, as determined by atomic force microscopy. Both the first-
and second-order Raman spectra show unique signatures of the number of layers in the
film. The n GL film analogue of the Raman G-band in graphite exhibits a Lorentzian line …
Results of room-temperature Raman scattering studies of ultrathin graphitic films supported on Si (100)/SiO2 substrates are reported. The results are significantly different from those known for graphite. Spectra were collected using 514.5 nm radiation on films containing from n = 1 to 20 graphene layers, as determined by atomic force microscopy. Both the first- and second-order Raman spectra show unique signatures of the number of layers in the film. The nGL film analogue of the Raman G-band in graphite exhibits a Lorentzian line shape whose center frequency shifts linearly relative to graphite as ∼1/n (for n = 1 ωG ≈ 1587 cm-1). Three weak bands, identified with disorder-induced first-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 second-order bands are also observed (∼2450, ∼2700, and 3248 cm-1). They are analogues 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 second-order band is more intense than the G-band.
ACS Publications