Towards chirality control of graphene nanoribbons embedded in hexagonal boron nitride

Abstract

The integrated in-plane growth of two dimensional materials (e.g. graphene and hexagonal boron nitride (h-BN)) with similar lattices, but distinct electrical properties, could provide a promising route to achieve integrated circuitry of atomic thickness. However, fabrication of edgespecific graphene nanoribbons (GNR) in the lattice of h-BN still remains an enormous challenge for present approaches. Here we developed a twostep growth method and successfully achieved sub-5 nm-wide zigzag and armchair GNRs embedded in h-BN, respectively. Further transport measurements reveal that the sub-7 nm-wide zigzag GNRs exhibit openings of the band gap inversely proportional to their width, while narrow armchair GNRs exhibit some fluctuation in the bandgap-width relationship. Transistors made of these GNRs with large bandgaps (>0.4 eV) exhibit excellent electronic performance even at room temperature (e.g. conductance on-off ratio more than 10 5 and carrier mobility more than 1,500 cm 2 V −1 s −1 ). An obvious conductance peak is observed in the transfer curves of 8-10 nm-wide zigzag GNRs while it is absent in most of armchair GNRs of similar width. Magneto-transport experiments show that zigzag GNRs exhibit relatively small magneto-conductance (MC) while armchair GNRs have much higher MC than zigzag GNRs. This integrated lateral growth of edge-specific GNRs in h-BN brings semiconducting building blocks to atomically thin layer, and will provide a promising route to achieve intricate nanoscale electrical circuits on high-quality insulating h-BN substrates.Graphene nanoribbons (GNRs), a quasi-one-dimensional graphene nanostructure, can exhibit either quasi-metallic or semiconducting behavior, depending on its specific chirality, including width, lattice orientation, and edge structure [ 1 ]. The unique properties of GNR make it a promising substitute to engineer prospective nano-electronics. There are two groups of GNRs, that differ by the edge type and are called zigzag (ZZ) and armchair (AC) [2]. Recent experiments [3,4] show that zigzag graphene nanoribbons (ZGNRs) potentially offer exotic electronic properties, such as ferromagnetism and half metallicity. Theory [5 ] predicts that all armchair graphene nanoribbons (AGNRs) are semiconducting with a band gap that is inversely proportional to their width. Normally, both ZGNRs and AGNRs have distinct electronic states and scattering properties [6,7] as well as unique chemical properties [8,9]. Practically, their edges are prone to intrinsic and extrinsic modifications [10][11][12]. Recent hetero-integration of graphene with h-BN by both van der Waals stacking [13,14] and in-plane covalent bonding [15][16][17][18][19] has exhibited an advantage in high chemical/mechanical stability, and may lead to emergent electronic properties that are fundamentally distinct from those of the constituents. However, such a hetero-structure with chirality-controllable GNRs is still difficult to achieve.In this work, we report the successful control over the chirality of mono-layer GNRs direc...

Atomically‐Precise Texturing of Hexagonal Boron Nitride Nanostripes

“…This makes hBN‐covered metals excellent platforms to achieve functional interfaces with atoms, molecules, and aggregates, as well as to develop hybrid 2D materials, such as twisted van der Waals stacks or 2D heterostructures. [ 6 , 7 , 8 ] The latter hold a great potential for atomically thin circuitry, such as superstructures formed with isostructural graphene, [ 9 , 10 , 11 , 12 , 13 ] which are optimal to engineer gaps and doping, as well as to tune and enhance spin scattering. However, exploiting fine hBN‐based nanostructures requires structural quality down to the atomic scale, which lies beyond current lithographic capabilities.…”

Understanding adsorption geometry of organometallic molecules on graphite

“…Bandgap control in graphene is one of the most important and tantalizing research topics in the graphene community because it may ultimately enable new applications in digital electronics 6 , 7 , pseudospintronics 8 , terahertz technology 9 , 10 , and infrared nanophotonics 11 , 12 . A number of approaches have been proposed or implemented to control the bandgap in graphene, such as using uniaxial strain 13 , 14 , graphene–substrate interactions 15 , 16 , lateral confinement 17 , and breaking the inversion symmetry in bilayer graphene 18 . Among them, adhering or bonding the atoms/molecules on the graphene surface can effectively control the bandgap because of the large surface-to-volume ratio of atoms/molecules that can be easily adsorbed on its surface 19 , 20 .…”

Understanding Adsorption Geometry of Organometallic Molecules on Graphene

“…[1][2][3][4][5] Bandgap control in graphene is one of the most important and tantalizing research topics in the graphene community because it may ultimately enable new applications in digital electronics, 6,7 pseudospintronics, 8 terahertz technology, 9,10 and infrared nanophotonics. 11,12 A number of approaches have been proposed or implemented to control the bandgap in graphene, such as using uniaxial strain, 13,14 graphene-substrate interactions, 15,16 lateral con nement, 17 and breaking the inversion symmetry in bilayer graphene. 18 Among them, adhering or bonding the atoms/molecules on the graphene surface can effectively control the bandgap because of the large surface-to-volume ratio of atoms/molecules that can be easily adsorbed on its surface.…”