Materials in Vacuum

Summary

A superficial view of a high or ultrahigh vacuum pumping system gives an impression of simplicity: clean, polished metal or glass surfaces, viewports, electrical and motion feedthroughs, piping, and pumps. In this chapter, the authors review the outgassing and structural properties of metals, glasses, ceramics, and polymeric materials used in the construction of vacuum systems. Stainless steel is the dominant material of construction for sophisticated processes, and its structural properties are discussed in some detail. Vaporization, permeation, and outgassing are important properties to vacuum performance. Vapor pressure determines the useful upper‐pressure limit for any material. Desorption from vacuum chamber surfaces provides an additional gas load to the system. Certain materials are rather impermeable to gases, whereas others allow certain gases to permeate from the atmospheric side. These effects, collectively referred to as outgassing, limit the ultimate system pressure.