Chemical Vapor Deposition Synthesis and Terahertz Photoconductivity of Low-Band-Gap N = 9 Armchair Graphene Nanoribbons

Abstract

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 N = 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·V·s.

Structure-dependent electrical properties of graphene nanoribbon devices with graphene electrodes

“…It is noted that the intensity of Raman signals can vary depending on the excitation wavelength and absorption of the specific GNR at this wavelength, and thus cannot be simply used to assess their composition. More detailed characterization by means of optical spectroscopy, scanning probe (AFM, STM) and optical terahertz photoconductivity can be found in our previous reports [38], [39] .…”

“…Structurally defined armchair GNRs were synthesized by the on-surface CVD and UHV methods through polymerization and graphitization of dihalogenated monomers on a metal surface [24], [38], [39] . The synthesis method allows the growth of GNR with well-defined edge structure and tunable width by the suitable choice of the starting molecular monomer.…”

“…In particular, it is observed that the GNR films are made by a dense layer of GNRs with average length of about 10 nm, with the longest extending up to 35 nm [38,39] .…”

“…In this work, we investigate the electrical behavior of CVD-grown AGNRs films with different widths and hence different electronic bandgaps. Namely, we used 5-AGNR, [38] 9-AGNR, [39] and 5n-AGNR, [38] where 5 and 9 indicate the number of carbon atom along the ribbon width and the sample labelled 5n-AGNR is a mixture containing mainly 10-AGNR and also some amounts of 5-, 15-, and 20-AGNRs (see section 2.2 for details). Moreover, the 9-AGNR sample was prepared also by the UHV method [35] , to compare the behavior of GNRs with the same width but different length.…”

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…As ac onsequence of the excellent physicochemical properties of graphene,ag reat amount of effort has been made by researchers to prepare atomically precise graphene nanoribbons (GNRs). Theg eneral concept for the rational synthesis of such assemblies employing aC DH reaction usually includes two steps:1)anon-surface polymerization of ah alogenated small-molecule precursor by ah omolytic cleavage of the carbon-halogen bond after evaporation onto ac lean noble metal surface under an ultrahigh vacuum and 2) aCDH sequence at elevated temperature,which yields the fully conjugated nanoribbon structure.F ollowing this concept, many atomically precise GNRs have been prepared from the corresponding molecular precursors (Scheme 30; GNR 217, [263] 219, [264] 221, [265] 223, [266] 225, [267] 227, [268] 229, [269] and 231 [127] ). Thep hysicochemical properties of such GNRs may by altered not only by changing the size of the assemblies (Scheme 30 A), but also by doping with heteroatoms (Scheme 30 B) or changing the edge structure of the GNRs (Scheme 30 C).…”