Small bandgap in atomically precise 17-atom-wide armchair-edged graphene nanoribbons

Abstract

Bottom-up synthesis of graphene nanoribbons (GNRs) may open new possibilities in future electronic devices owing to their tunable electronic structure, which depends strongly on their well-defined width and edge geometry. For instance, armchair-edged GNRs (AGNRs) exhibit width-dependent bandgaps. However, the bandgaps of AGNRs synthesized experimentally so far are relatively large, well above 1 eV. Such a large bandgap may deteriorate device performance due to large Schottky barriers and carrier effective masses. Here, we describe the bottom-up synthesis of AGNRs with smaller bandgaps, using dibromobenzenebased precursors. Two types of AGNRs with different widths, namely 17 and 13 carbon atoms, were synthesized on Au(111), and their atomic and electronic structures were investigated by scanning probe microscopy and spectroscopy. We reveal that 17-AGNRs have the smallest bandgap, as well as the smallest electron/hole effective mass, among bottom-up AGNRs reported so far. The successful synthesis of 17-AGNRs is a significant step toward the development of GNR-based electronic devices.

Atomically precise graphene nanoribbons: interplay of structural and electronic properties

“…It has a small band gap of 0.19 eV on Au(111) and with FT-STS an effective mass m CB = m VB = 0.06 m e was found. 56 From the experimental characterization of AGNRs, the three predicted D families become apparent in accordance with theory. When selecting AGNRs for devices, a tradeoff has to be made between band gap and effective mass, where wider band gaps lead to larger effective carrier masses and therefore, lower electron mobility.…”

“…Using such a design strategy, atomically precise 9-, 13-and 17-AGNRs have been successfully synthesized. 56,57 In addition, steric hindrance has also been identified as a useful concept for the synthesis of cGNRs and chGNRs.…”

“…198 Recently, the 13-AGNR was also synthesized from 16 by Yamaguchi et al on Au (111). 56 This leads to a ribbon with identical interior, but notably with a different edge orientation at the termini. They reported a similar band gap of 1.34 eV.…”

“…It has a small band gap of 0.19 eV on Au(111) and with FT-STS an effective mass m CB = m VB = 0.06 m e was found. 56 …”

On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

“…To this end, on-surface synthesis based on the polymerization and planarization of tailor-made molecular precursors on metal surfaces under ultrahigh vacuum (UHV) conditions appears particularly powerful and offers the additional advantage of in-situ monitoring by atomic-resolution scanning probe microscopy [5][6][7][8][9][10]. Since the initial demonstration of 7-atomwide armchair-type GNRs (7-AGNRs) on a Au(111) surface using 10,10'-dibromo-9,9'-bianthryl (DBBA) as a precursor [11], a range of GNRs with different structures have been prepared via on-surface synthesis, such as armchair GNRs (N-AGNRs) with different widths N (N = 5, 6, 8, 9, 10, 13, 15 and 17) [12][13][14][15][16][17][18][19], zigzag GNRs (ZGNRs) [20], chevron-type GNRs [11,21], chiral (3,1)-GNRs containing zigzag and armchair edges [22], and heteroatom-doped GNRs with boron, nitrogen, oxygen, or sulfur [23][24][25][26][27][28][29][30]. π-Extension of 7-AGNRs through aryl-substitution of DBBA turned out to be of special value.…”