科研之友
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摘要
Single-molecule nanomagnets have unique quantum properties, and their potential applications require characterization and accessibility of individual single-molecule magnets on various substrates. We develop a gentle tip-deposition method to bring individual prototype single-molecule magnets, manganese-12-acetate (Mn-12) molecules, onto the semimetallic Bi(111) surface without linker molecules, using low-temperature scanning tunneling microscopy. We are able to identify both the almost flat-lying and side-lying orientations of Mn-12 molecules at 4.5 K. Energy-resolved spectroscopic mapping enables the first observation of several molecular orbitals of individual Mn-12 molecules in real space, which is consistent with density functional theory calculations. Both experimental and theoretical results suggest that an energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the almost flat lying Mn-12 is only 40% of such a gap for an isolated (free) Mn-12 molecule, which is caused by charge transfer from the metallic surface states of Bi to the Mn-12. Despite the reduction of this gap, STM images show that the local lattices of Bi(111) covered with Mn-12 remain essentially intact, indicating that Mn-12-Bi interactions are not strong. Our findings,open an avenue to address directly the local structural and electronic properties of individual single molecule magnets on solid substrates.
