Raman spectroscopy of lithographically patterned graphene nanoribbons

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Graphene nanoribbons (GNRs) exhibit unique properties due to quantum confinement.
• Understanding GNR behavior is crucial for advanced electronic applications.

Purpose of the Study:

• To investigate the effects of size and edge structure on GNR properties using Raman spectroscopy.
• To explore the reliability of Raman spectral features for characterizing GNRs.

Main Methods:

• Fabrication of GNRs with widths from 15 to 100 nm via e-beam lithography and oxygen plasma etching.
• Analysis of Raman spectra, focusing on the G, D, and 2D bands.
• Investigation of photothermal effects and susceptibility to doping.

Main Results:

• Raman spectra of narrow GNRs show an upshifted G band and a prominent D band related to ribbon edges.
• The D-to-G band intensity ratio increases with decreasing width, with a notable decrease below 25 nm.
• GNRs exhibit enhanced susceptibility to photothermal effects and reversible doping compared to bulk graphene.
• The 2D band remains a reliable indicator of layer number, even with broadening in narrow GNRs.

Conclusions:

• Raman spectroscopy effectively characterizes GNRs, revealing quantum confinement and edge effects.
• Edge amorphization influences spectral features and provides estimates for D mode relaxation length.
• GNRs demonstrate distinct doping behaviors and photothermal sensitivity.
• The 2D band's utility for layer determination is confirmed for narrow GNRs.