An Outline of Surface Science

My principal objective in Section 10.4 has been to underline the necessity for a drastic enhancement of a crucial experimental technology, the production of ultrahigh vacuum, as a precondition for the emergence of a new branch of science, and this enhancement was surveyed in the preceding Section. It would not be appropriate in this book to present a detailed account of surface science as it has developed, so 1 shall restrict myself to a few comments. The field has been neatly subdivided among chemists, physicists and materials scientists it is an ideal specimen of the kind of study which has flourished under the conditions of the interdisciplinary materials laboratories described in Chapter 1. 

UHV is necessary but not sufficient to ensure an uncontaminated surface. Certainly, the surface will not be contaminated by atoms arriving from the vacuum space, but such contamination as it had before the vacuum was formed has to be removed by bombardment with argon ions. This damages the surface structurally, and that has to be healed by in situ heat treatment. That, however, allows dissolved impurities to diffuse to the surface and cause contamination from below. This problem has to be dealt with by many cycles of bombardment and annealing, until the internal contaminants are exhausted. This is a convincing example of Murphy s Law in action one of the many corollaries of the Law is that new systems generate new problems . 

One other technique has become central in surface research this is X-ray photoelectron spectrometry, earlier known as ESCA, electron spectroscopy for chemical analysis . Photoelectrons are emitted from a surface irradiated by X-rays. The precautions which have to be taken to ensure accurate quantitative analysis by this much-used technique are set out by Seah (1980). 

As remarked above, surface science has come to be partitioned between chemists, physicists and materials scientists. Physicists have played a substantial role, and an excellent early overview of surface science from a physicist s perspective is by Tabor (1981). An example of a surface parepisteme that has been entirely driven by physicists is the study of the roughening transition. Above a critical temperature but 

An excellent, accessible overview of what surface scientists do, the problems they address and how they link to technological needs is in a published lecture by a chemist, Somorjai (1998). He concisely sets out the function of numerous advanced instruments and techniques used by the surface scientist, all combined with UHV (LEED was merely the first), and exemplifies the kinds of physical chemical issues addressed - to pick just one example, the interactions of co-adsorbed species on a surface. He also introduces the concept of surface materials , ones in which the external or internal surfaces are the key to function. In this sense, a surface material is rather like a nanostructured material in the one case the material consists predominantly of surfaces, in the other case, of interfaces. 

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