non-conservative current-induced forces · current-induced forces 1 . electromigration h.b....
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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
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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
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Towards microscopic understanding of current induced forces
Theory is mostly phenomenological
Experiments probing forces on atomic scale are almost absent
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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)
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Atomic water wheel
D. Dundas, E.J. McEniry, T.N. Todorov, Nature Nanotechnol., 4, 99-102 (2009).
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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”
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Model system: two degrees of freedom Lü, Brandbyge, Hedegård, Nano Lett. 10, 1657 (2010).
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A model system: chain of Au atoms
Lü, Brandbyge, Hedegård, Nano Lett. 10, 1657 (2010).
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Experiments of current-induced breaking
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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
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Pt chain: higher energy runaway mode
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Pt chain: higher energy runaway mode
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Can we do these experiments in a more controlled way?
Atomic Chain
STM Tip
Molecule
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“The Beast”
Au (111) atomic resolution
Electronic edge states
Low-temperature STM
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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)
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Single atom manipulation: Au on Au(111)
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Single atom manipulation: Au on Au(111)
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Single atom manipulation: Au on Au(111)
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Single atom manipulation: Au on Au(111)
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Single atom manipulation: Au on Au(111)
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Single atom manipulation: Au on Au(111)
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Connected chain formation
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Connected chain formation
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Connected chain formation
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Three atoms chain
Connected chain formation
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Single-molecule conductors
Fournier (Tautz) et al., PRB 84, 035435 (2011)
Courtesy: Wagner C.
47 cycles
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Single-molecule conductors
Fournier (Tautz) et al., PRB 84, 035435 (2011) 37
Atomic Chain
STM Tip
Building atomic conductors between tip and sample
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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
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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
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