current

force force ?

Current-induced forces

1

Electromigration

H.B. Heersche et al., Appl. Phys. Lett. 91, 072107 (2007). 2

Indium atom transport over CNT

Regan, Aloni, Ritchie, Dahmen, Zettl, Nature 428, 924 (2004)

TEM image

current

CNT

In nano- particle

current

current

3

Atomic steps on Ag(111)

Boncharduk et al., Phys.Rev.Lett. 99, 206801 (2007) 4

Current induced cleaning of graphene

Moser, Barreiro, Bachtold, Appl.Phys.Lett. 91, 163513 (2007) 5

Basic concepts of electromigration

EeZeZF wd

**

Effective valence. For metals typically ̶ 20 … ̶ 50

Direct force: associated with Landauer dipole

6

Towards microscopic understanding of current induced forces

Theory is mostly phenomenological

Experiments probing forces on atomic scale are almost absent

7

Current induced single-atom switching

Schirm et al. Nature Nanotechnol. 8, 645 (2013) 8

Current-induced single switching

Tierney et al., Nature Nanotechn. 6, 625 (2011) See also: Perera et al., Nature Nanotechn. 8, 46 (2013)

STM of molecules adsorbed to Cu(111)

1 nm

Low tunnel current (molecule not rotating)

9

10

Atomic water wheel

D. Dundas, E.J. McEniry, T.N. Todorov, Nature Nanotechnol., 4, 99-102 (2009).

11

The Berry force Lü, Brandbyge, Hedegård, Nano Lett. 10, 1657 (2010).

Semi-classical Langevin equation for the motion of ion cores

The electron wavefunction ϕ depends on the positions of the ions R. Projecting out the electronic states,

Leads to an effective “magnetic field”

12

Model system: two degrees of freedom Lü, Brandbyge, Hedegård, Nano Lett. 10, 1657 (2010).

13

A model system: chain of Au atoms

Lü, Brandbyge, Hedegård, Nano Lett. 10, 1657 (2010).

14

Experiments of current-induced breaking

15

Experiments of current-induced breaking

Smit, Untiedt, van Ruitenbeek, Nanotechnol. 15, S472 (2004). 16

Experiments of current-induced breaking

Smit, Untiedt, van Ruitenbeek, Nanotechnol. 15, S472 (2004). 17

Experiments of current-induced breaking

Sabater, Untiedt, van Ruitenbeek, to be published 18

Experiments of current-induced breaking

Sabater, Untiedt, van Ruitenbeek, to be published

Initial stability test at 10mV

19

Pt chain: higher energy runaway mode

20

Pt chain: higher energy runaway mode

21

Can we do these experiments in a more controlled way?

Atomic Chain

STM Tip

Molecule

22

“The Beast”

Au (111) atomic resolution

Electronic edge states

Low-temperature STM

23

Deposition of single atoms by low-T evaporation

Au ad-atoms over Au(111) surface 24

Lateral manipulation of atoms

STM Tip

PRL 79, 697 (1997) J. Vac. Sci. Technol., B 23(2005)

25

Single atom manipulation: Au on Au(111)

26

Single atom manipulation: Au on Au(111)

27

Single atom manipulation: Au on Au(111)

28

Single atom manipulation: Au on Au(111)

29

Single atom manipulation: Au on Au(111)

30

Single atom manipulation: Au on Au(111)

31

Connected chain formation

32

Connected chain formation

33

Connected chain formation

34

Three atoms chain

Connected chain formation

35

Single-molecule conductors

Fournier (Tautz) et al., PRB 84, 035435 (2011)

Courtesy: Wagner C.

47 cycles

36

Single-molecule conductors

Fournier (Tautz) et al., PRB 84, 035435 (2011) 37

Atomic Chain

STM Tip

Building atomic conductors between tip and sample

38

3-dimensional STM control

x y z

feedback

Force field simulation 39

3D motion sensor

x,y,z

Initialize program Load libraries

Define variables and classes

Load system (Tip + surface + ad atoms)

Move the Base atoms of tip

Relax system for new tip position

Print the new state of the system

End

Visual feedback

z* (V) x* (V)

y*(V)

Tunnelling current feedback

Force Field Simulation

Interatomic potential1: Second-moment approximation (SMA) to the tight-binding Hamiltonian

Base atoms

1. R Cortes Huerto (Saul) et al., PRB 88, 235438 (2013) 40

Possible process suggested by simulation

41

STM control: The game

x y z

feedback

Force field simulation 42

Can also do break junctions

x y z

feedback

Force field simulation 43

The team Christian Wagner Sumit Tewari Jacob Bakermans Federica Galli Roel Smit Carlos Untiedt Carlos Sabater Tadashi Shiota Raphael Muller Marius Trouwborst Sasha Vrbica Irene Battisi Elena Tartaglini Jan Aarts

Support from Sylvestre Bonnet Tchavdar Todorov Daniel Dundas Mads Brandbyge Stefan Tautz

44 LeidenCenterUltramicroscopy

Conclusions

45

46