Lateral Force Microscopy Reveals the Energy Barrier of a Molecular Switch
| Autor: | Alfred J. Weymouth, Bianca Simmet, Oliver Gretz, Franz J. Giessibl, Elisabeth Riegel |
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| Rok vydání: | 2021 |
| Předmět: |
Molecular switch
Materials science General Engineering General Physics and Astronomy 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Molecular physics 0104 chemical sciences law.invention Bond length law Metastability Microscopy Molecule General Materials Science Scanning tunneling microscope 0210 nano-technology Ground state Quantum tunnelling |
| Zdroj: | ACS nano. 15(2) |
| ISSN: | 1936-086X |
| Popis: | Copper phthalocyanine (CuPc) is a small molecule often used in organic light emitting diodes where it is deposited on a conducting electrode. Previous scanning tunneling microscopy (STM) studies of CuPc on Cu(111) have shown that inelastic tunneling events can cause CuPc to switch between a ground state and two symmetrically equivalent metastable states in which the molecule is rotated. We investigated CuPc on Cu(111) and Ag(111) with STM and lateral force microscopy (LFM). Even without inelastic events, the presence of the tip can induce rotations and upon closer approach, causes the rotated states to be favored. Combining STM measurements at various temperatures and LFM measurements, we show that the long-range attraction of the tip changes the potential energy landscape of this molecular switch. We can also determine the geometry of the rotated and ground states. We compare our observations of CuPc on Cu(111) to CuPc on Ag(111). On Ag(111), CuPc appears flat and does not rotate. Stronger bonding typically involves shorter bond lengths, larger shifts of energy levels, and structural stability. Although the binding of CuPc to Cu(111) is stronger than that on Ag(111), the nonplanar geometry of CuPc on Cu(111) is accompanied by two metastable states which are not present on the Ag(111) surface. |
| Databáze: | OpenAIRE |
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