Tunable Magnetic Coupling in Graphene Nanoribbon Quantum Dots

Authors

Peter H. Jacobse, University of California, Berkeley
Mamun Sarker, University of Nebraska-LincolnFollow
Anshul Saxena, University of Texas at Austin
Brookhaven National Laboratory, Brookhaven National Laboratory
Ziyi Wang, University of California, Berkeley, Lawrence BerkeleyNational Laboratory
Emma Berger, University of California, Berkeley
Narayana R. Aluru, University of Texas at Austin
Alexander Sinitskii, University of Nebraska-LincolnFollow
Michael F. Crommie, University of California, Berkeley, Lawrence BerkeleyNational Laboratory

Document Type

Article

Date of this Version

2-27-2024

Citation

Small 2024, 20, 2400473. DOI: 10.1002/smll.202400473

Comments

Open access.

Abstract

Carbon-based quantum dots (QDs) enable flexible manipulation of electronic behavior at the nanoscale, but controlling their magnetic properties requires atomically precise structural control. While magnetism is observed in organic molecules and graphene nanoribbons (GNRs), GNR precursors enabling bottom-up fabrication of QDs with various spin ground states have not yet been reported. Here the development of a new GNR precursor that results in magnetic QD structures embedded in semiconducting GNRs is reported. Inserting one such molecule into the GNR backbone and graphitizing it results in a QD region hosting one unpaired electron. QDs composed of two precursor molecules exhibit nonmagnetic, antiferromagnetic, or antiferromagnetic ground states, depending on the structural details that determine the coupling behavior of the spins originating from each molecule. The synthesis of these QDs and the emergence of localized states are demonstrated through high-resolution atomic force microscopy (HR-AFM), scanning tunneling microscopy (STM) imaging, and spectroscopy, and the relationship between QD atomic structure and magnetic properties is uncovered. GNR QDs provide a useful platform for controlling the spin-degree of freedom in carbon-based nanostructures.