Views:5 Author:Site Editor Publish Time: 2017-07-03 Origin:Site
Sputter coating, also known as “cathodic sputtering”, is using the erosive action of accelerated ions at the surface of a target material.
These ions have enough energy to remove (=sputter) particles at the target surface. In its simplest form, under high vacuum an electrical field is generated between an anode and a cathode plate (target) that is to be sputtered. By means of electrical voltage a working gas, generally Argon (Ar), is ionized generating a glow discharge.
Since the target is kept at negative voltage, the positive Ar+ ions accelerate towards the target and “sputter” the atoms on its surface. In contrast to thermal evaporation, in sputtering the particles of the target are not displaced by heat, but by means of direct “momentum transfer” (inelastic collision) between the ions and the atoms of the material to be deposited. To accomplish sputtering a certain threshold energy is needed to remove atoms from the target surface and bring them into the vacuum. This is indicated by the sputtering efficiency S, which is the ratio of the sputtered material per Ar+ion.
Sputtering processes have much higher energy than evaporation processes which means that the sputtered material is usually in the form of ions with the ability to generate very dense coatings.