Materials and Technologies for Green Energy
Contact person: Mazzer Massimo
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Sputtering is a deposition process that exploits the emission of atoms from the surface of a material (target) due to the bombardment of energetic particles, typically positive ions of an inert gas. The process is triggered by the formation of a plasma from a gas (inert as Ar or reactive as O2 and N2) with charged particles. These phenomena depend strongly on the kinetic energy of the incident particles; when the latter exceeds the binding energy of the solid atoms, a change of the reticular structure of the target occur. If the mass of the incident ion is less than that of the target atom, the ion can be reflected; if instead the mass of the ion is greater than that of the man of the target, both will leave the collision point heading towards the inside of the target. The emission of a target atom is the result of a cascade of collisions: a single collision would not be able to produce a velocity component exiting the surface of the target and opposite to the original direction of the incident ion. An important parameter relating to the yield of sputtering is the angle of incidence of the ion with respect to the normal to the target surface. The atoms released by the ion bombardment are mainly neutral atoms, which will not be affected by the applied electric field and will be deposited on a support placed a few cm from the target, used as a substrate. The peculiarity of the Sputtering technique is that the target material undergoes a solid-to-gas phase transition: for this reason Sputtering is called a PVD (Physical Vapor Deposition) technique. A more detailed description of the sputtering technique, in particular applied to “green energy” materials, can be found in Giulia Spaggiari's webinar, available below.