Book chapter 4

Introduction to Surface and Thin Film Processes

John A. Venables

Cambridge University Press (2000)

Supplementary notes by John A. Venables

© Arizona Board of Regents for Arizona State University and John A. Venables

Chapter 4: Surface processes in adsorption

Corrections, comments and updates

4.1 Chemi- and physi-sorption

New references for section 4.1

4.2 Statistical physics of adsorption at low coverage

On page 109, there is an elementary mistake in the definition of the chemical potential, µa, in equation 4.3. This does not affect the result, as the last equality is correct. However, µa is not equal to F/Na, but to dF/dNa. This makes no difference if the chemical potential is linear in Na, but the configurational term is not linear, having the extra ln(Na) terms in Stirling's approximation. You can check this definition and derivation to source using the reference to Hill's book given on page 109, or by reminding yourself of the definition of dF = ... + µdN in equation E.8, page 315.

New references for section 4.2

4.3 Phase diagrams and phase transitions

On page 115, there is an "obvious" error in the caption to figure 4.3. In the last line it should state ".. at 97.4 K only the G to S transition occurs;..."

New references for section 4.3

4.4 Physisorption: interatomic forces and lattice dynamical models

In section 4.4.4 on page 127, figure 4.11a contains an insert labelled TPD, and is referred to in the text as TDS. The acronym TPD stands for the technique, Temperature Programmed Desorption: TDS stands for Thermal Desorption Spectrum, or Spectroscopy, as given in the text and Appendix B on page 308.

A whole class of thermal desorption and reaction spectroscopies exists, and a suitable introduction is provided by Woodruff and Delchar (1986, 1994), chapter 5. TPRS (Temperature Programmed Reaction Spectroscopy) is especially useful, in conjunction with other (electron) spectroscopies, in determining the reaction products and intermediates in reacting chemisorbed systems. A particularly insightful description of how early research developed in this field is provided by Madix (1994).

New references for section 4.4

4.5 Chemisorption: quantum mechanical models and chemical practice

In section 4.5.2 on page 133, reference is made to Appendix D, my Web-based resources page. Of particular interest is the Simulations page. Let me know by email if there are useful, more specific, links that could usefully be linked to this page.

Also in this section 4.5.2 on pages 132-133, the R-5 interaction is mentioned, with reference to the chapter by T.L. Einstein (1996); this dependence is due to coupling of adsorbates via bulk electronic states. Theorists have also shown that there can be coupling via surface states, which is much more long-ranged, varying as R-2 for pair interactions (Lau & Kohn, 1978), and R-2.5 for trio interactions, as described by Hyldgaard & Einstein (2002, 2003). These interactions have been demonstrated by low temperature STM experiments of adatoms on smooth metal surfaces, which show not only an oscillatory long range interaction, but also a short-range repulsion, which impedes two adatoms coalescing to form a dimer. Annealing experiments have been used to quantify the magnitude of this repulsive energy for Cu adatoms on Cu(111), using the analysis methods discussed in chapter 5 (Venables & Brune, 2002).

In section 4.5.4 on page 135-136, I argue for need for patience in understanding catalysis. However, the opportunities for theoretical understanding of commercially catalysts have advanced in great strides during the last 5 years. Some of this progress is reviewed in outline by three of the main European players (Nørskov, Scheffler and Toulhoat, 2006), emphasizing the role played by Density Functional Theory. The idea that one may be able to design a real catalyst from a scientific starting point is no longer fanciful. Many recent references are given to enable one to explore this rapidly developing and hugely important area. This article and references would be relevant for anyone tackling Project 4.4 on page 143.

In section 4.5.4 on page 139-140, I describe the use of Photoemission electron microscopy (PEEM) to study the dynamics of surface reactions. There are several more recent reviews of progress with this technique, including that by Rotermund (1999).

New references for section 4.5

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Latest version 12 October 2006, format corrected 16 Feb 09.