Thin-film thickness monitors, deposition rate controllers, and so on, are a family of instruments used in high and ultra-high vacuum systems.
Not surprisingly, the devices which control some aspect of the process tend to be called controllers, and those that simply monitor the process tend to be called monitors.
Many other techniques might be used, depending on the thickness and characteristics of the thin film, including surface profilers, ellipsometry, dual polarisation interferometry and scanning electron microscopy of cross-sections of the sample.
Many thickness monitors and controllers allow tooling factors to be entered into the device before deposition begins.
where Fi is the initial tooling factor, Ti is the film thickness indicated by the instrument, and Tm is the actual, independently measured thickness of the deposited film.