Evaporation Processes

Abstract

Physical vapor deposition (PVD) technology consists of the basic techniques of evaporation deposition and sputter deposition. PVD is used to deposit films and coatings or self-supported shapes such as sheet, foil, tubing, etc. The thickness of the deposits can vary from angstroms to millimeters.Applications range widely, from decorative to utilitarian and over significant segments of the engineering, chemical, nuclear, microelectronics, and related industries. They have been increasing rapidly because modern high technology demands multiple and often conflicting sets of properties from engineering materials, e.g., combination of two or more of the following: high temperature strength, impact strength, specific optical, electrical or magnetic properties, wear resistance, fabricability into complex shapes, biocompatibility, cost, etc. A single or monolithic material cannot meet such demands. The solution is a composite material, a core material and a coating each having the requisite properties to meet the specifications.This article will review evaporation-based deposition technologies, theory and mechanisms, processes, deposition of various types of materials, and also the evolution of the microstructure and its relationship to the properties of the deposits.The first evaporated thin films were probably prepared by Faraday in 1857 when he exploded metal wires in a vacuum. The deposition of thin metal films in vacuum by Joule heating was discovered in 1887 by Nahrwold and was used by Kundt in 1888 to measure refractive indices of such films. In the ensuing period, the work was primarily of academic interest, concerned with optical phenomena associated with thin layer of metals, research into kinetics and diffusion of gases, and gas-metal reactions.