Diffusion on surfaces
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Diffusion on surfaces. TR Linderoth et al. Phys. Rev. Lett. 82 (1999) 1494 Aarhus Universitet. Surface Science Course 2006 Achim Schnadt. Surface diffusion is important for. ... growth processes. A. Groß, Theoretical Surface Science , Springer-Verlag. ... surface reactions.

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Diffusion on surfaces

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Diffusion on surfaces

Diffusion on surfaces

TR Linderoth et al.

Phys. Rev. Lett. 82 (1999) 1494

Aarhus Universitet

Surface Science Course 2006 Achim Schnadt


Diffusion on surfaces

Surface diffusion is important for ...

... growth processes

A. Groß, Theoretical Surface Science, Springer-Verlag

... surface reactions

G. Ertl, Lecture at Nobel Symposium

Energy in Cosmos, Molecules and Life, July 2005


Diffusion on surfaces

Which particles do diffuse on surfaces?

Chemisorption, physisorption, and precurors

Image from

J. V. Barth, Surf. Sci. Rep. 40 (2000) 75


Diffusion on surfaces

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949

Tekniska Högskolan, Helsingfors

Brown University, Rhode Island

Università di Genova


Diffusion on surfaces

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949

Tekniska Högskolan, Helsingfors

Brown University, Rhode Island

Università di Genova


Diffusion on surfaces

Classical movement

Quantum tunnelling

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949

Tekniska Högskolan, Helsingfors

Brown University, Rhode Island

Università di Genova

only for hydrogen!


Diffusion on surfaces

Some theory ...

Following the treatment in

A. Groß,

Theoretical Surface Science,

Springer-Verlag


Diffusion on surfaces

A. Zangwill, Physics at Surfaces,

Cambridge University Press


Diffusion on surfaces

Initial state – transition state – final state

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949

Single jump diffusion on a fcc(100) metal surface. A. Groß, Theoretical Surface Science, Springer-Verlag.


Diffusion on surfaces

What would you expect for the diffusion on a stepped surface?

(take into account what you’ve just learned about transition states)


Diffusion on surfaces

What would you expect for the diffusion on a stepped surface?

(take into account what you’ve just learnt about transition states)

”Ehrlich-Schwoebel-barrier”

G. Ehrlich, F. G Hudda, J. Chem. Phys. 44 (1966) 1039

R. K. Schwoebel, J. Appl. Phys. 40 (1969) 614


Diffusion on surfaces

Single (nearest neighbour)

jumps

Image from

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949


Diffusion on surfaces

Single (nearest neighbour)

jumps

Long jumps

Image from

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949


Diffusion on surfaces

Single (nearest neighbour)

jumps

Long jumps

Depends on the energy dissipation rate

and the temperature!

Image from

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949


Diffusion on surfaces

Another mechanism for diffusion: Exchange diffusion

Transition state

Final state

Initial state

Exchange diffusion on a fcc(100) metal surface. A. Groß, Theoretical Surface Science, Springer-Verlag.


Diffusion on surfaces

A different view on downward diffusion at steps

Image from

T. Ala-Nissila, R. Ferrando, S. C. Ying

Adv. Phys. 51 (2002) 949


Diffusion on surfaces

Island diffusion on Pt(110) (2x1)

T.R. Linderoth et al.

Phys. Rev. Lett. 82 (1999) 1494

Aarhus Universitet


Diffusion on surfaces

Island diffusion on Pt(110) (2x1)

T.R. Linderoth et al.

Phys. Rev. Lett. 82 (1999) 1494

Aarhus Universitet


Diffusion on surfaces

Single-particle diffusion coefficient and chemical diffusion coefficient


Diffusion on surfaces

Experimental techniques for studying surface diffusion

Local probe techniques

Field ion microscopy

Image from

A. Zangwill, Physics at Surfaces. Cambridge University Press

Originally from G. Ehrlich,

CRC Crit. Rev. Sol. State Mat. Sci. 10 (1982) 391

Scanning tunnelling microscopy

M. Schunack et al., University of Aarhus

More STM movies on http://www.ifa.au.dk/spm


Diffusion on surfaces

Experimental techniques for studying surface diffusion

Integrating methods

Laser-induced thermal desorption


Diffusion on surfaces

Experimental techniques for studying surface diffusion

Integrating methods

Quasielastic helium scattering

Graphs from A.P. Graham, A. Menzel, J.P. Toennies, J. Chem. Phys. 111 (1999) 1676


Diffusion on surfaces

Experimental techniques for studying surface diffusion

Integrating methods

Photoelectron emission microscopy

[1-10]

O/Pt(110)

50 mm x 190 mm

Time between images: 120 s

A. von Oertzen, H. H. Rotermund, S. Nettesheim, Surf. Sci. 311 (1994) 322


Diffusion on surfaces

Want to know more?

Experiment review (plus some theory):

J. V. Barth, Surf. Sci. Rep. 40 (2000) 75

Theory review (easy to read!):

T. Ala-Nissila, R. Ferrando, S. C. Ying, Adv. Phys. 51 (2002) 949


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