16 - Epitaxy

Summary

Introduction

Our account of adsorption to this point has been restricted largely to one particular, albeit important, special case: the situation where adsorbate–substrate interactions dominate adsorbate–adsorbate interactions. This is sufficient for discussion of the vast majority of interesting chemical processes that occur at surfaces. Important inter-adsorbate forces surely come into play – there would be no surface reactions otherwise – but what counts the most is just the fact that the species do in fact find themselves on a surface. This is what we mean by heterogeneous catalysis.

The rules of the game change somewhat when we consider the other major driving force for research into our subject: the microelectronics industry. Here, surface physics per se is not so crucial as the closely related field of interface physics. The interfaces in question typically involve the junction of two micron-sized wafers of metal, semiconductor, ceramic, etc. Since these junctions break translational invariance, it is unsurprising that certain ideas (such as interface localized electronic and vibrational states) reappear almost unchanged. But a great many new features enter which would carry us far outside the intended scope of this book. Luckily, there is one aspect of the problem which does fall within our purview: the concept of epitaxy and epitaxial growth.