Solution-Synthesized Chevron Graphene Nanoribbons Exfoliated onto H:Si(100)

Abstract

There has been tremendous progress in designing and synthesizing graphene nanoribbons (GNRs). The ability to control the width, edge structure, and dopant level with atomic precision has created a large class of accessible electronic landscapes for use in logic applications. One of the major limitations preventing the realization of GNR devices is the difficulty of transferring GNRs onto nonmetallic substrates. In this work, we developed a new approach for clean deposition of solution-synthesized atomically precise chevron GNRs onto H:Si(100) under ultrahigh vacuum. A clean transfer allowed ultrahigh-vacuum scanning tunneling microscopy (STM) to provide high-resolution imaging and spectroscopy and reveal details of the electronic structure of chevron nanoribbons that have not been previously reported. We also demonstrate STM nanomanipulation of GNRs, characterization of multilayer GNR cross-junctions, and STM nanolithography for local depassivation of H:Si(100), which allowed us to probe GNR-Si interactions and revealed a semiconducting-to-metallic transition. The results of STM measurements were shown to be in good agreement with first-principles computational modeling.

Laterally extended atomically precise graphene nanoribbons with improved electrical conductivity for efficient gas sensing

“…While high-resolution STM images of cGNRs were demonstrated, the downside of this approach was that even in UHV conditions it is difficult to entirely remove the residual solvent molecules and other contaminants that adsorb on the Au (111) surface during the sample preparation in air. Recently, we demonstrated an alternative sample preparation approach, the dry contact transfer (DCT) method, by which it is possible to prepare cleaner samples of solution-synthesized GNRs for STM analysis 37 . In brief, in this method a GNR powder is annealed in UHV to remove adsorbates and solvent residues, and then pressed against an already prepared, clean substrate for STM imaging using a fiber-glass applicator.…”

Aggregation of atomically precise graphene nanoribbons

“…2 Based on the STM analysis that we provide in our previous publications, these GNRs ranged from several to several tens of nm in length. 2,45 Our prior studies on the solutionsynthesized GNRs also include the results of their bulk characterization by spectroscopic techniques, such as XPS, EDX, NMR, UV-vis-NIR, FTIR and Raman spectroscopy. 2,5,44 Unlike other solution-synthesized GNRs that have been recently reported, 3,4,7,[9][10][11]13,49 these chevron GNRs do not contain any alkyl groups to increase their solubility.…”

“…71,72 While it is difficult to visualize the packing of GNRs on Si/ SiO 2 or mica, this could be done on a conductive substrate, such as Au(111), using scanning tunneling microscopy (STM), a technique that is capable of imaging GNRs with nearly atomic resolution. 2,42,45,73,74 Fig. 3d shows STM image of GNRs on Au(111) substrate.…”

“…These nanoribbons already have been a subject of several theoretical [39][40][41] and experimental studies. 2,5,[42][43][44][45][46][47][48] We investigated chevron GNRs in solution and found that their optical properties depend on their aggregation state. We also found that in addition to forming bulk aggregates of the p-p stacked nanoribbons, on surfaces GNRs can assemble to form long one-dimensional (1D) structures.…”

Carbon-Based Materials for Thermoelectrics

“…Connecting same or different types of GNRs into a chain or quasi-1D superlattice is one of the most studied strategies for achieving better ZT properties. For instance, 1D wiggle-like GNR, or graphene nanowiggle (GNW), has been synthesized with atomistic precision using a bottom-up technique [102], of which the microscopy image is shown in Figure 7(a) [103] and the schematic atomic structure is shown in Figure 7(b). Such GNW structure can be viewed as periodic repetitions of graphene nanoribbon junctions.…”