Nanostructured coatings made by oblique deposition with sputtering

A low-cost approach to fabricate nanostructured coatings will be presented: oblique deposition with sputtering. This technique is energetically efficient and environmentally friendly, since it takes place at room tem perature in one single step and no chemicals are involved (thus without recycling problems). Any kind of flat substrate can be used, and with feasible modifications, it can be scaled up to large surfaces. The growth regimes [1-3] and the deposition rate [4] of the nanostructured coatings obtained using two different materials, gold and titanium, will be discussed. It will be shown that the formation of nanostructures is the outcome of self-shadowing effects when vapor species arrive at the film surface along a tilted direction (see Figure). In fact, we have developed a fundamental framework to explain the different morphologies obtained, the key factor being the thermalization degree of sputtered particles that accounts for the collisional processes in the vapor phase between the travelling atoms and the plasma species. In particular, at low pressures, tilted nanocolumns can be obtained when the angle of incidence surpasses a critical threshold. Moreover, if substrate rotation is used, the majority of nanostr uctures becomes axially symmetric. Several applications of such nanocolumnar coatings will be reviewed, especially focusing in two of them: black metals [5] and antibacterial coatings [6].