3 research outputs found
Monitoring the On-Surface Synthesis of Graphene Nanoribbons by Mass Spectrometry
We present a mass spectrometric approach
to characterize and monitor
the intermediates of graphene nanoribbon (GNR) formation by chemical
vapor deposition (CVD) on top of Au(111) surfaces. Information regarding
the repeating units, lengths, and termini can be obtained directly
from the surface sample by a modified matrix-assisted laser desorption/ionization
(MALDI) method. The mass spectrometric results reveal ample oxidative
side reactions under CVD conditions that can be drastically diminished
by the introduction of protective H<sub>2</sub> gas at ambient pressure.
Simultaneously, the addition of hydrogen extends the lengths of the
oligophenylenes and thus the final GNRs. Moreover, the prematurely
formed cyclodehydrogenation products during the oligomer growth can
be assigned by the mass spectrometric technique. The obtained mechanistic
insights provide valuable information for optimizing and upscaling
the bottom-up fabrication of GNRs. Given the important role of GNRs
as semiconductors, the mass spectrometric analysis provides a readily
available tool to characterize and improve their structural perfection
Lateral Fusion of Chemical Vapor Deposited <i>N</i> = 5 Armchair Graphene Nanoribbons
Bottom-up
synthesis of low-bandgap graphene nanoribbons with various
widths is of great importance for their applications in electronic
and optoelectronic devices. Here we demonstrate a synthesis of <i>N</i> = 5 armchair graphene nanoribbons (5-AGNRs) and their
lateral fusion into wider AGNRs, by a chemical vapor deposition method.
The efficient formation of 10- and 15-AGNRs is revealed by a combination
of different spectroscopic methods, including Raman and UV–vis-near-infrared
spectroscopy as well as by scanning tunneling microscopy. The degree
of fusion and thus the optical and electronic properties of the resulting
GNRs can be controlled by the annealing temperature, providing GNR
films with optical absorptions up to ∼2250 nm
Chemical Vapor Deposition Synthesis and Terahertz Photoconductivity of Low-Band-Gap <i>N</i> = 9 Armchair Graphene Nanoribbons
Recent
advances in bottom-up synthesis of atomically defined graphene
nanoribbons (GNRs) with various microstructures and properties have
demonstrated their promise in electronic and optoelectronic devices.
Here we synthesized <i>N</i> = 9 armchair graphene nanoribbons
(9-AGNRs) with a low optical band gap of ∼1.0 eV and extended
absorption into the infrared range by an efficient chemical vapor
deposition process. Time-resolved terahertz spectroscopy was employed
to characterize the photoconductivity in 9-AGNRs and revealed their
high intrinsic charge-carrier mobility of approximately 350 cm<sup>2</sup>·V<sup>–1</sup>·s<sup>–1</sup>