On-surface synthesis and characterization of carbon nanoribbon heterojunctions from a single precursor

Heterojunctions of carbon nanoribbons (CNRs) hold great promise for electronic device applications due to their enhanced carrier separation efficiency induced by built-in electric fields at the junctions. Moreover, their electronic, magnetic, and optical properties can be finely tuned by precisely controlling the width and edge structure. However, the fabrication of CNR heterojunctions typically requires multiple distinct precursor molecules, demanding complex chemical design and synthesis. Here, we report the successful on-surface synthesis of a quasi-one-dimensional CNR heterojunction using a single molecular precursor. The heterojunction is formed by bridging <i>cis</i> and <i>trans</i> configured CNRs. Scanning tunneling spectroscopy and differential conductance (d<i>I</i>/d<i>V</i>) mapping reveal distinct differences in the electronic band structures of the <i>cis</i>-, <i>trans</i>-, and heterojunction structures, demonstrating that geometric configuration plays a key role in modulating the electronic properties. This work establishes a straightforward strategy for synthesizing and characterizing quasi-one-dimensional carbon-based polymer heterojunctions. It also offers a promising pathway for designing carbon-based p-n heterojunctions for future nanoelectronic and optoelectronic applications.