Atomic Force Microscopy Reveals Bistable Configurations of Dibenzo[a,h]thianthrene and their Interconversion Pathway

Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany.
Physical Review Letters (Impact Factor: 7.51). 02/2012; 108(8):086101. DOI: 10.1103/PhysRevLett.108.086101
Source: PubMed


We investigated dibenzo[a,h]thianthrene molecules adsorbed on ultrathin layers of NaCl using a combined low-temperature scanning tunneling and atomic force microscope. Two stable configurations exist corresponding to different isomers of free nonplanar molecules. By means of excitations from inelastic electron tunneling we can switch between both configurations. Atomic force microscopy with submolecular resolution allows unambiguous determination of the molecular geometry, and the pathway of the interconversion of the isomers. Our investigations also shed new light on contrast mechanisms in scanning tunneling microscopy.

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    • "Eventually, the energy barriers E a calculated for the AB→BA conversion are comparable with those estimated for conventional FE oxides, such as PbTiO 3 for which E a ∼ 0.1 − 0.2 eV /formula unit, as well as with that of the recently predicted 1T FE phase of MoS 2 [39], suggesting that the polarization reversal could be experimentally accessible. Inelastic electron excitations from a STM tip could be also used to switch between the two FE phases, as recently proposed for bistable molecular switches[40] [41]. "
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