PACVD (Plasma Assisted Chemical Vapour Deposition) is a process for forming solid thin films through atomic or molecular deposition, or a combination of both, on a heated surface. The resulting coating comes from a chemical reaction where the precursors are in the vapour phase. The PACVD process takes place at lower temperatures than the CVD process, because it is the plasma that is used to trigger a thermal reaction, rather than thermal energy. In this process all the materials that create the film are in the gas phase, unlike in the CVD process where at least one of the materials is in the solid phase (usually a metal).