Thin films

Abstract

This chapter provides an extended introduction to the basic principles of thin-film technology thin filmtechnology, including deposition processes, structure, and some optical and electrical properties relevant to this volume. The material is accessible to scientists and engineers with no previous experience in this field, and contains extensive references to both the primary literature and earlier review articles. Although it is impossible to provide full coverage of all areas or of the most recent developments in this survey, references are included to enable the reader to access the information elsewhere, while the coverage of fundamentals will allow this to be appreciated. Deposition of thin films by the main physical deposition methods deposition method of vacuum evaporation, molecular-beam epitaxy and sputtering are described in some detail, as are those by the chemical deposition methods of electrodeposition, chemical vapour deposition and the Langmuir–Blodgett technique. Examples of structural features of some thin films thin film are given, including their crystallography, larger-scale structure and film morphology. The dependence of these features on the deposition conditions are stressed, including those required for the growth of epitaxial films and the use of zone models in the morphological characteristics classification of the morphological characteristics. The main optical properties of thin films are reviewed, including the use of Fresnel coefficients at media boundaries, reflectance and transmittance, matrix methods and the application of these techniques to the design of antireflection coatings, mirrors and filters. The dependence of electrical conductivity (or resistivity) and the temperature coefficient of resistivity in metallic thin films is discussed, in particular the models of Thomson, Fuchs–Sondheimer and the grain-boundary model of Mayadas–Shatzkes. For insulating and semiconducting thin films the origin and effects of several high-field conduction processes are examined, including space-charge-limited conductivity, the Poole–Frenkel effect, hopping, tunnelling and the Schottky effect. Finally, some speculations regarding future developments are made.