Deposition of Porous Nanocolumnar Thin Films by Magnetron Sputtering

Physical vapor deposition (PVD) encompasses a large variety of thin-film growth methods involving the ejection of atoms from a target and their arrival to a substrate, where these species accumulate in the form of a film. A large variety of experimental results sustain the application of sputtering techniques for the preparation of compact thin films of interest as protective layers, passive optical applications or hard coatings. A key issue for the structuration of magnetron sputtered thin films in the form of nanocolumns is to modify the deposition geometry, placing the substrate at an oblique angle with respect to the racetrack of the target. A relevant aspect concerning the angular distribution of sputtered species relates to the state of the target and, in particular, to the racetrack profile. The concept of thermalization degree introduces a very useful quantity to qualitatively assess the energy and angular distribution of the species upon deposition.