Diffusion on surfaces Surface Science Course 2006 Achim Schnadt TR Linderoth et al. Phys. Rev. Lett. 82 (1999) 1494 Aarhus Universitet

Surface diffusion is important for... G. Ertl, Lecture at Nobel Symposium Energy in Cosmos, Molecules and Life, July growth processes... surface reactions A. Groß, Theoretical Surface Science, Springer-Verlag

Image from J. V. Barth, Surf. Sci. Rep. 40 (2000) 75 Chemisorption, physisorption, and precurors Which particles do diffuse 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

T. Ala-Nissila, R. Ferrando, S. C. Ying Adv. Phys. 51 (2002) 949 Tekniska Högskolan, Helsingfors Brown University, Rhode Island Università di Genova

Quantum tunnelling only for hydrogen! Classical movement T. Ala-Nissila, R. Ferrando, S. C. Ying Adv. Phys. 51 (2002) 949 Tekniska Högskolan, Helsingfors Brown University, Rhode Island Università di Genova

Some theory... Following the treatment in A. Groß, Theoretical Surface Science, Springer-Verlag

A. Zangwill, Physics at Surfaces, Cambridge University Press

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.

What would you expect for the diffusion on a stepped surface? (take into account what you’ve just learned about transition states)

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

Single (nearest neighbour) jumps Image from T. Ala-Nissila, R. Ferrando, S. C. Ying Adv. Phys. 51 (2002) 949

Single (nearest neighbour) jumps Long jumps Image from T. Ala-Nissila, R. Ferrando, S. C. Ying Adv. Phys. 51 (2002) 949

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

Exchange diffusion on a fcc(100) metal surface. A. Groß, Theoretical Surface Science, Springer-Verlag. Another mechanism for diffusion: Exchange diffusion Initial state Transition stateFinal state

A different view on downward diffusion at steps Image from T. Ala-Nissila, R. Ferrando, S. C. Ying Adv. Phys. 51 (2002) 949

T.R. Linderoth et al. Phys. Rev. Lett. 82 (1999) 1494 Aarhus Universitet Island diffusion on Pt(110) (2x1)

T.R. Linderoth et al. Phys. Rev. Lett. 82 (1999) 1494 Aarhus Universitet Island diffusion on Pt(110) (2x1)

Single-particle diffusion coefficient and chemical diffusion coefficient

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

Laser-induced thermal desorption Integrating methods Experimental techniques for studying surface diffusion

Integrating methods Experimental techniques for studying surface diffusion Graphs from A.P. Graham, A. Menzel, J.P. Toennies, J. Chem. Phys. 111 (1999) 1676 Quasielastic helium scattering

Photoelectron emission microscopy Integrating methods Experimental techniques for studying surface diffusion O/Pt(110) 50  m x 190  m Time between images: 120 s [1-10] A. von Oertzen, H. H. Rotermund, S. Nettesheim, Surf. Sci. 311 (1994) 322

Want to know more? Theory review (easy to read!): T. Ala-Nissila, R. Ferrando, S. C. Ying, Adv. Phys. 51 (2002) 949 Experiment review (plus some theory): J. V. Barth, Surf. Sci. Rep. 40 (2000) 75