Manipulation of Phosphangulene on Ag(111) with a low-temperature STM
R. Lin*, a, U. Quaadea, K. Stokbroa, F. C. Krebsb, K.-F. Braunc, G. Meyerd, K.-H. Riederc
aMikroelektronik Centret, Building 345 east,Technical University of Denmark, DK-2800, Lyngby, Denmark bDepartment of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark cInstitut für Experimentalphysik, Freie Universitaet, Arnimallee 14,14159 Berlin, Germany dPaul Drude Institut für Festkoerperelektronik, Hausvogteiplatz 5-7,10117 Berlin, Germany
A pyroelectric molecule, phosphangulene, was investigated and manipulated using a low-temperature scanning tunneling microscope (STM) at 6 K. The molecules was deposited at 30 K on a clean Ag(111) single-crystal substrate The lateral manipulations of phosphangulene provide valuable information for understanding the movement of complex molecules at metal surface, and the controlled positioning of phosphangulene yields useful knowledge necessary to fabricate a nanoscale device with molecules.
Lateral manipulation is possible via tip-adsorbate interaction employing a tunneling resistance of 10 MW. The manipulation curves show that the molecule is pulled due to attractive forces. Reducing the gap resistance to 0.2 MW and hence the distance between tip and molecule results in pushing due to repulsive forces. It is also found that with this gap resistance the molecule altered its adsorption configuration during lateral manipulations. Different molecular adsorption configurations were identified on the substrate, as shown in the Figure together with the schematic molecular models.
Furthermore, it was found that by applying voltage pulses in the vicinity of and direct at the molecules different changes in the adsorption configurations occurred. We have identified lateral movement, rotation, and inversion/flipping of the molecules. Based on the measurements we suggest that different mechanisms are involved.
Technical University of Denmark,
DK-2800, Lyngby, Denmark