The impact of an atom or ion on a surface results in ejection of atoms from the surface as a result of collisions and momentum transfer from the incoming particle. This process is known as sputtering. Unlike many other vapour phase techniques, there is no melting of the material. The sputtering process is illustrated above and is most commonly used for thin-film deposition of many different materials including metals and ceramics. Ions impacting on the target can liberate sputtered neutrals. The number of neutrals per incident ion is known as the sputter yield (Y) and the sputtering rate (R) is dependant on the current of ions (I) to the target and the sputter yield. The sputter rate is an imprtant factor when looking at process efficiency. So,

                                                R∝I.Y(E)

But, the energy of the incoming ions is simply the voltage on the cathode and the yield is approximately linear with energy (E). Therefore,

                                                                      Y(E) ∝ E ∝ V

                                                and

                                                                      R ∝ I.V = Power

The energy of the sputtered neutrals is given by,

                                                                     
                   where     E = energy of sputtered material
                                  E_B = surface binding energy of target
                                 f(E) = probability of a sputtered neutral being emitted with energy, E




The sputter yield for some materials can be seen below.