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▲ [20a-E308-8] Electron-induced vibrations of a single water molecule encapsulated in a C60 fullerene
Keywords:electron transport, single water molecule
The encapsulation of a single water molecule inside a buckyball [1] provides a unique opportunity to study the dynamics of a single water molecule, since the endofullerene structure can suppress the effect of hydrogen-bond networks by isolating water molecules. However, most of the studies on the H2O@C60 molecules have been performed on a large ensemble of molecules; only a few have been done at the single-molecule level [2].
Here, we have investigated the electron transport through single H2O@C60 molecules by using the single molecule transistor (SMT) geometry [3], as shown in Fig. 1(a). The fullerene works as a natural cage to trap a H2O molecule [1]. Using the source and drain electrodes separated by a sub-nm gap, we captured a single H2O@C60 molecule in the nanogap electrodes. By performing transport measurement, we have obtained a Coulomb stability diagram of a single-H2O@C60 SMT for the first time. As shown in Fig. 1(b), single electron tunneling area shows six excited states below 25 meV with unequal energy spacings. These tunnel-electron-induced excited states are attributed to the librational motions of the encapsulated H2O molecule in a C60 cage, which is in consistent with DFT calculations and the result of ensemble measurements.
The present result demonstrates that the endofullerene structure together with nanogap electrodes provides a sub-nm-size laboratory for studying single-molecule dynamics.
Reference:
[1] K. Kurotobi, and Y. Murata, Science 333, 613 (2011). [2] S. Fujii, et al., Phys. Chem. Chem. Phys. 21, 12606 (2019). [3] S. Q. Du, et al., Nature Photon. 12, 608 (2018).
Here, we have investigated the electron transport through single H2O@C60 molecules by using the single molecule transistor (SMT) geometry [3], as shown in Fig. 1(a). The fullerene works as a natural cage to trap a H2O molecule [1]. Using the source and drain electrodes separated by a sub-nm gap, we captured a single H2O@C60 molecule in the nanogap electrodes. By performing transport measurement, we have obtained a Coulomb stability diagram of a single-H2O@C60 SMT for the first time. As shown in Fig. 1(b), single electron tunneling area shows six excited states below 25 meV with unequal energy spacings. These tunnel-electron-induced excited states are attributed to the librational motions of the encapsulated H2O molecule in a C60 cage, which is in consistent with DFT calculations and the result of ensemble measurements.
The present result demonstrates that the endofullerene structure together with nanogap electrodes provides a sub-nm-size laboratory for studying single-molecule dynamics.
Reference:
[1] K. Kurotobi, and Y. Murata, Science 333, 613 (2011). [2] S. Fujii, et al., Phys. Chem. Chem. Phys. 21, 12606 (2019). [3] S. Q. Du, et al., Nature Photon. 12, 608 (2018).