ИСТИНА

Understanding of molecular switching between different charge states is crucial to further progress in molecule-based nano-electronic devices. Scanning tun- neling microscopy (STM) is one of the most promising techniques for imaging of prototype molecular devices and testing their properties. We employed scan- ning tunnelling microscopy to study the structure of ultrathin molecular layer C60film grown on the WO2/W(110) surface and reveal a correlation between charge state of a individual C60 molecule and it orientation. Tunnelling junc- tion based on individual C60 molecule is stable below temperature of kinetic rotational transition of 220K [1] when all molecules are static. However, in the temperature range of 220–260 K some isolated molecules switch between high- and normal- conductance states. At high temperatures the molecules ro- tate continuously so fast that no ”blinking” is observed and all molecules appear as perfect spheres [2]. High-conductance state arises due to charging of the C60 , which causes changes in the local density of electron states near Fermi level and consequently a variation in tunnelling current. Using density func- tional theory calculations, these states were suggested to be: charge-neutral C60; negatively charged C60, which has accepted an electron. Such molecules appear in STM topography as flashing nano-bulbs on the surface. Switching of the molecule conductance state is accompanied by change of molecule orbital structure detected in STM topography that proves change of orientation of the molecule during switching. Molecular movement accompanies the molecule’s switching between these states; as the molecule rotates, it exchanges charge with the substrate, gaining or loosing an electron. [1]Sergey I. Bozhko et.al.,Phys. Rev. B.84, 195412 (2011). [2]Sergey A. Krasnikov et.al.,Nano Res.4(2), 194–203 (2011).