2D abrupt nano-junctions blending sp-sp2 bonds on atomically precise heterostructures

TL;DR

This paper reports the successful on-surface synthesis of atomically precise 2D heterostructures blending sp and sp2 hybridized carbon bonds, demonstrating their potential for tunable electronic properties in nanoscale devices.

Contribution

It introduces a novel synthesis method for covalently bonded sp-sp2 heterostructures between graphene nanoribbons and graphdiyne, revealing their formation mechanism and electronic properties.

Findings

Achieved up to 71% bonding efficiency through controlled removal of by-products.

Discovered that the heterostructure exhibits voltage-tunable current separation.

Provided atomic-resolution insights into covalent bond formation mechanisms.

Abstract

Two-dimensional heterostructures combining sp-sp2 hybridization,blending graphene with graphyne-based allotropes, offer substantial potential for enhancing the tunability of electronic and transport properties while providing significant structural flexibility. These attributes are desirable for next generation nanoscale electronic applications. Despite such potential, their experimental realization remains elusive, as synthesized carbon heterostructures are limited to doped, graphene-based systems exhibiting exclusively sp2 hybridization. Here, we demonstrate the on-surface synthesis of covalently bonded sp-sp2 lateral heterostructures between graphene nanoribbons and graphdiyne networks on Au(111). Atomic-resolution scanning tunnelling microscopy, combined with density functional theory, reveals the formation mechanism of the covalent interfacial bonds between nanoribbons and graphdiynes, also highlighting the key role of surface chemistry. Bromine atoms deriving from the molecules dehalogenation and chemisorbed along the nanoribbon inhibit the junction formation, but bonding efficiency can be boosted up to 71% by controlled removal of these by-products. Electronic structure and transport calculations show that the 2D heterostructure by itself is characterized by disentangled properties for the two subsystems, forming an atomically narrow junction enabling voltage-tunable spatial current separation in two dimensions. There results define a viable strategy for engineering graphene-based sp-sp2 heterostructures, paving the way for the design and synthesis of all-carbon nanoscale electronic architectures.