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Towards chirality control of graphene nanoribbons embedded in hexagonal boron nitride

(Nanowerk News) Graphene nanoribbons (GNRs) are one-dimensional strips of graphene that can exhibit either quasi-metallic or semiconducting behavior, depending on its specific chirality, including width, lattice orientation, and edge structure. The unique properties of GNR make it a promising substitute to engineer prospective nano-electronics.
There are two groups of GNRs that differ by edge type: zigzag (ZZ) and armchair (AC), which have been extensively studied in terms of synthesis approach and properties. However, fabrication of edge-specific sub-5 nm GNRs on the insulating substrate still remains a significant challenge.
Recently, a team led by Prof. Haomin Wang in Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), reported the successful control over the chirality of GNRs embedded in hexagonal boron nitride (h-BN) nano-trenches, whose direction can be modulated by different catalytic cutting particles.
Both ZGNRs and AGNRs narrower than 5 nm are successfully synthesized. STEM investigation shows that in-plane epitaxy was realized at the boundary of graphene and h-BN with controlled chirality at the edge along the GNR while developed laterally.
Further electrical investigation reveals that all narrow ZGNRs exhibit a bandgap larger than 0.4 eV while narrow AGNRs exhibit a relatively large variation in band-gap. Transistors made of GNRs with large bandgaps exhibit on-off ratios of more than 105 at room temperature with carrier mobilities higher than 1,500 cm2V-1s-1.
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.
This paper has been published online in Nature Materials ("Towards chirality control of graphene nanoribbons embedded in hexagonal boron nitride").
Wang’s group has been working on the synthesis of graphene and its nanostructures on h-BN for many years. Through introducing the silane as the gaseous catalyst, a quick growth of large single-crystalline graphene (Nat. Commun., 6, 6499 (2015)) and control over edge of graphene (Nanoscale, 9, 11475 (2017)) were achieved on h-BN. Subsequently, the synthesis of oriented GNRs was reported on h-BN through the template approach (Nat. Commun., 8, 14703 (2017)).
Source: Shanghai Institute of Microsystem and Information Technology
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