Raman Spectroscopy Confirms Nanoscale Alignment of GNRs

Graphene nanoribbons (GNRs) are a novel class of quasi-onedimensional conductors which are just one atom thick, few atoms (~ 1 nm) wide and currently a few tens of nanometers long. After their synthesis on gold substrates in ultra-high vacuum one obtains films of GNRs with a size of a few square millimeters. The individual GNRs can be randomly oriented or aligned in parallel, depending on the surface structure of the substrate. In the latter case, this allows for the development of polarisation-dependent optical methods to investigate the properties of GNR-films on a larger scale.
Raman spectroscopy is a relatively well-established technique that enables the determination of direction and degree of alignment of GNRs and other elongated nanostructures – also via the polarization of the laser used for excitation and on a variety of different substrates.
We have therefore used this method to characterize 7-atom wide GNRs on their gold substrate and after transfer to glass. Afterwards, our collaborators from the University of Berkeley could show that they can use polarization-dependent absorption spektroscopy on just a monolayer of GNRs to verify their optical bandgap. Congrats Sihan!

Sihan Zhao, Gabriela Borin Barin, Ting Cao, Jan Overbeck, Rimah Darawish, Tairu Lyu, Steve Drapcho, Sheng Wang, Tim Dumslaff, Akimitsu Narita, Michel Calame, Klaus Müllen, Steven G. Louie, Pascal Ruffieux, Roman Fasel, and Feng Wang. Optical Imaging and Spectroscopy of Atomically Precise Armchair Graphene Nanoribbons. Nano Letters 2020, 20 (2), 1124-1130 DOI: 10.1021/acs.nanolett.9b04497