Editing Sputtering (section)

=== Sputter damage ===
Sputter damage is usually defined during transparent electrode deposition on optoelectronic devices, which is usually originated  from the substrate's bombardment by highly energetic species. The main species involved in the process and the representative energies can be listed as (values taken from<ref name="Aydin 3549–3584">{{Cite journal|last1=Aydin|first1=Erkan|last2=Altinkaya|first2=Cesur|last3=Smirnov|first3=Yury|last4=Yaqin|first4=Muhammad A.|last5=Zanoni|first5=Kassio P. S.|last6=Paliwal|first6=Abhyuday|last7=Firdaus|first7=Yuliar|last8=Allen|first8=Thomas G.|last9=Anthopoulos|first9=Thomas D.|last10=Bolink|first10=Henk J.|last11=Morales-Masis|first11=Monica|author11-link= Mónica Morales Masis |date=2021-11-03|title=Sputtered transparent electrodes for optoelectronic devices: Induced damage and mitigation strategies|journal=Matter|language=English|volume=4|issue=11|pages=3549–3584|doi=10.1016/j.matt.2021.09.021|s2cid=243469180|issn=2590-2393|doi-access=free|hdl=10754/673293|hdl-access=free}}</ref>):

* Sputtered atoms (ions) from the target surface (~10 eV), the formation of which mainly depends on the binding energy of the target material;
* Negative ions (originating from the carrier gas) formed in the plasma (~5–15 eV), the formation of which mainly depends on the plasma potential;
* Negative ions formed at the target surface (up to 400 eV), the formation of which mainly depends on the target voltage;
* Positive ions formed in the plasma (~15 eV), the formation of which mainly depends on the potential fall in front of a substrate at floating potential;
* Reflected atoms and neutralized ions from the target surface (20–50 eV), the formation of which mainly depends on the background gas and the mass of the sputtered element.

As seen in the list above, negative ions (e.g., O<sup>−</sup> and In<sup>−</sup> for ITO sputtering) formed at the target surface and accelerated toward the substrate acquire the largest energy, which is determined by the potential between target and plasma potentials. Although the flux of the energetic particles is an important parameter, high-energy negative O<sup>−</sup> ions are additionally the most abundant species in plasma in case of reactive deposition of oxides. However, energies of other ions/atoms (e.g., Ar<sup>+</sup>, Ar<sup>0</sup>, or In<sup>0</sup>) in the discharge may already be sufficient to dissociate surface bonds or etch soft layers in certain device technologies.  In addition, the momentum transfer of high-energy particles from the plasma (Ar, oxygen ions) or sputtered from the target might impinge or even increase the substrate temperature sufficiently to trigger physical (e.g., etching) or thermal degradation of sensitive substrate layers (e.g. thin film metal halide perovskites).

This can affect the functional properties of underlying charge transport and passivation layers and photoactive absorbers or emitters, eroding device performance. For instance, due to sputter damage, there may be inevitable interfacial consequences such as pinning of the Fermi level, caused by damage-related interface gap states, resulting in the formation of Schottky-barrier impeding carrier transport. Sputter damage can also impair the doping efficiency of materials and the lifetime of excess charge carriers in photoactive materials; in some cases, depending on its extent, such damage can even lead to a reduced shunt resistance.<ref name="Aydin 3549–3584"/>