Physical vapor deposition is a technique to coat substrates with thin films. The coating material is hereby at first evaporated and then condensed at the substrate.
The substrate and the coating material are in a vacuum chamber. The coating material is evaporated. This can be achieved by different methods like electron beam, laser beam, arc discharge or sputtering. Since the coating material is the physical target in the evaporation process it is called target. The evaporated material is accelerated away from the target and diffuses to the substrate. As soon the vapor hits its surface it condenses forming a coating.
PVD can only be performed in a high vacuum. It is the preferred method to deposit metals and alloys because no chemical reaction takes place. It is nevertheless also possible to initiate a chemical reaction. For example oxygen can be applied to the chamber to create oxide coatings.
Sputtering is a method to evaporate the target material. The noble gas argon is hereby applied to the chamber and a plasma is ignited. The target is electrically charged so that the argon ions of the plasma are accelerated towards the target. They hit it with such a high energy that atoms are ejected from the target. As a noble gas is used no chemical reaction takes place.
Cathodic arc deposition is another method to evaporate the coating material. The target is electrically negative charged and becomes the cathode of an electrical arc. The arc is ignited by applying high voltage to a special tip. The ions in the arc hit the cathode heating it up and cathode material is evaporated. The energy of the ions in the arc and of the evaporated material is much higher than in the sputter process. This allows to deposit hard coatings of e.g. chromium or metal nitrides.
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