Applications in energy, optics and electronics

Abstract

Thin films play a vital role in nearly all electronic and optical devices. They have long been familiar as antireflection coatings on window glass, video screens, camera lenses and other optical devices; these are generally films less than 100 nm thick made from a transparent (dielectric) material with a refractive index less than that of the substrate. In solar-energy conversion, similar layers of thin films are now serving as antireflection coatings on solar-energy collectors; semitransparent metal films are used in Schottky-barrier solar cells; combinations of thin films are used for photothermal devices that generate low- or high-grade heat; and thin semiconductor films on metal or glass substrates form a promising type of low-cost solar cell. In integrated circuits, of course, thin films are pervasive: metal layers form all onchip electrical connections and gate regions for field-effect transistors, to name just two examples; oxide or nitride films form insulating barriers between other films; and layers of semiconductors are integral parts of all the structures. One of the newest applications of thin-film technologies is in circuits based films made from superconductors forming, for example, Josephson junctions such as the one shown in figure 1.