Abstract
Low temperature measurements of the tunneling current as a function of the applied bias voltage have been performed on a dense constant-height grid above individual copper phthalocyanine molecules adsorbed on a Cu(111) surface. By appropriate tuning of the applied bias, the molecule can be reversibly switched between two configurations in which pairs of opposite maxima appear rotated by in the tunneling current map. The underlying conformations are revealed by density functional calculations including van der Waals interactions: a symmetric ground state and two energetically equivalent states, in which the molecule is twisted and rotated around its center by . For tip biases above 200 mV position-dependent current switching is observed, as in previous measurements of telegraph noise [Schaffert et al., Nat. Mater. 12, 223 (2013)]. In a small voltage interval around zero the measured current becomes bistable. Switching to a particular state can be initiated by sweeping the voltage past well-defined positive and negative thresholds at certain positions above the molecule or by scanning at constant current and a reduced reverse bias.
- Received 6 November 2015
- Revised 2 October 2019
DOI:https://doi.org/10.1103/PhysRevB.100.155427
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