Program

Overview ▪ Monday ▪ Tuesday ▪ Wednesday ▪ Thursday ▪ Friday

Tuesday June 23

Tu1: Transport in electronic devices

Chair: D. Sanchez-Portal, San Sebastián, Spain

Contributed talk

Environmental control of single-molecule conductance

H. Okuyama¹,Y. Kitaguchi¹, S. Habuka¹, S. Hatta¹, T. Aruga¹, T. Frederiksen², M. Paulsson³, and H. Ueba⁴

¹Kyoto University, Kyoto, 606-8502, Japan

²DIPC, 20018 San Sebastian, Spain

³Linnaeus University, 391 82 Kalmar, Sweden

⁴University of Toyama, Toyama 930-8555, Japan

Electrical properties of single molecules have attracted much attention due to their potential use as basic components of electronics in the limits of miniaturization. To this end, significant experimental efforts have been devoted to make molecular junctions and probe their electrical properties. To precisely measure the conductance through a molecule, reliable connections of the metal probes to the molecule must be made. With scanning tunneling microscope (STM) junctions, one can bridge a 'target' molecule between the tip and substrate and reliably study the conductance through single molecules [1, 2]. Another characteristic of STM is that individual atoms and molecules can be manipulated on the surface with atomic-scale precision, which was used to investigate and control the interaction between them. To make good use of these advantages in the contact regime, it is important to preserve an identical tip-molecule contact geometry during repeated junction formation, which then enables one to compare the conductance through a single molecule on the surface in different arrangements and orientations of neighboring molecules.

Here we present such a non-destructive contact that uses a phenyl ring to reversibly connect the molecule to the tip electrode. In a prior work [3], we studied the adsorption of a phenoxy molecule on Cu(110) and found that it is bonded to the surface via an oxygen atom in a nearly flat configuration. When the STM tip is gradually approached to such a flat-lying phenoxy molecule on the surface at one point the molecule flips up and makes contact to the tip apex while remaining anchored to the Cu surface via the oxygen atom, thus forming a molecular junction between the two electrodes. Because the tip-phenyl interaction is relatively weak (π-bonding) as compared to that between molecule and substrate (covalent bonding), retraction of the tip causes cleavage at the same tip-phenyl interface, releasing the molecule to the original position on the surface without any perturbation of the tip apex. Thus, repeated switching of a phenoxy junction is feasible with this setup. This enables us to investigate the molecular conductance with unprecedented precision and to compare the conductance of a junction in different prearranged environments to reveal the impact of surrounding molecules.

[1] N. Neel et al., Phys. Rev. Lett. 98, 065502 (2007)

[2] W. Haiss et al., Nature Mater. 5, 995 (2006)

[3] Y. Kitaguchi et al., J. Chem. Phys. 139, 044708 (2013)