The substrate is placed in a high vacuum chamber at room temperature with a crucible containing the material to be deposited. A heating source is used to heat the crucible causing the material to evaporate and condense on all exposed cool surfaces of the vacuum chamber and substrate. The process is typically performed on one side of the substrate at a time. Typical sources of heating are: E-beam, Resistive heating, RF-inductive heating. In some systems the substrate can be heated during deposition to alter the composition/stress of the deposited material.