**1.1 Alloys sputtering**

The material surface sputtering induced by the irradiation is explained by Sigmund's theory or with modifications of itself. The phenomenological model developed by Sigmund employs the collision cascade as the fundamental event to explain the material surface sputtering: the incident ion upon collision with the solid initiates a series of atomic collisions with the surrounding atoms in the interaction volume, these atomic collisions are denominated the collision cascade. The incident ion energy is shared among those atoms that are located within of collisions cascade and promoted atomic detachment and atomic mobility. Only those collisions that occur near of material surface are effective in ejecting atoms out of the material surface. The great majority of atoms removed come from the first atomic layers of the material surface. The sputtering yield is the average number of atoms ejected from the material surface per incident ion. The sputtering yield depends on several things: the incidence angle at which ions collide with the material surface, the incoming ions energy, ions/surface atoms mass ratio, and the material surface binding energy. At a higher number of atomic collisions that occur in a near-surface region, the surface Sputtering Yield would be higher.

*Surface Microstructure Changes Induced by Ion Beam Irradiation DOI: http://dx.doi.org/10.5772/intechopen.112015*

The Sputtering Yields' main characteristics for complex materials as binary alloys are the same as a pure element, but there are additional complications since there are two different types of atoms in the material. The two species cannot be eroded at an equal rate due to differences in energy partitioning, being removed probability or binding energies. Experimentally, preferential sputtering of one atomic species over the other has been observed in many alloys or compounds [9].
