Plasma deposition of optical films and coatings: A review

Plasma enhanced chemical vapor deposition (PECVD) is being increasingly use d for the fabrication of transparent dielectric optical films and coatings. This involves single-layer, multilayer, graded index, and nanocomposite op tical thin film systems for applications such as optical filters, antirefle ctive coatings, optical waveguides, and others. Beside their basic optical properties (refractive index, extinction coefficient, optical loss), these systems very frequently offer other desirable "functional" characteristics. These include hardness, scratch, abrasion, and erosion resistance, improve d adhesion to various technologically important substrate materials such as polymers, hydrophobicity or hydrophilicity, long-term chemical, thermal, a nd environmental stability, gas and vapor impermeability, and others. In th e present article, we critically review the advances in the development of plasma processes and plasma systems for the synthesis of thin film high and low index optical materials, and in the control of plasma-surface interact ions leading to desired film microstructures. We particularly underline tho se specificities of PECVD, which distinguish it from other conventional tec hniques for producing optical films (mainly physical vapor deposition), suc h as fabrication of graded index (inhomogeneous) layers, control of interfa ces, high deposition rate at low temperature, enhanced mechanical and other functional characteristics, and industrial scaleup. Advances in this field are illustrated by selected examples of PECVD of antireflective coatings, rugate filters, integrated optical devices, and others. (C) 2000 American? Vacuum Society. [S0734-2101(00)03606-X].