**2. Production of thin films**

There is a myriad of technologies that can be used for the deposition of thin films. The choice of deposition process is dependent upon several factors, such as substrate structure and operating temperature. Several attempts have been made to classify deposition process, but they differ from the perspective of the authors that make these efforts. It is not the goal of this chapter to exhaustively list all the technologies. For that excellent books and reviews can be consulted, such as those of references [13–15].

Considering only the vacuum technologies, more recently, it is generally accepted that there are four general categories of thin film deposition: atomistic growth, particulate deposition, bulk coating and surface modification. Within these technologies especially emphasis will be given to sputtering, which is the technology used for the production of the thin films that are used for the medical and environmental applications described in the next section. Sputtering is one of the techniques of physical vapor deposition (PVD).

The properties of the films deposited by this sputtering depend on the material of the target, the gas used for the discharge and deposition parameters such as pressure, target-distance, polarization of the substrate and the chemical composition of the discharge gas. In fact, in addition to the nonreactive noble gas, the discharge gas, others can be added such as oxygen, nitrogen or methane. In this case, the sputtering is said to occur in a reactive mode. The use of a magnetron associated with

#### *Thin Films for Medical and Environmental Applications DOI: http://dx.doi.org/10.5772/intechopen.80021*

the cathode creates a magnetic field that imposes compulsory trajectories to the electrons ejected by the target, increasing the bombardment density.

The use of different power sources enables not only the deposition of electric conductive materials, direct current (DC) power supply, but also the deposition of ceramic and polymers, when radio frequency (RF) generators are used. Therefore, any material can have its surface changed by the deposition of any other type of material, similar or dissimilar, by sputtering. In order to better understand the enormous advantages of the use of sputtering, many excellent reviews have been published, namely a very recent one with an overview from the 1800s to 2017 [16].
