**1. Introduction**

In this introduction, a brief overview of the sputtering process is given based on a working class manuscript [1], but excellent reviews on the process have been published (see, e.g., Ref. [2]).

Sputtering is one of the techniques of coating a material by physical vapor deposition (PVD). Sputtering consists in the ejection of particles, atoms or clusters, by the bombardment of a solid or target by energetic particles, mostly ions. It results from collisions between the

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

incident energetic particles, and/or resultant recoil atoms, with surface atoms. A measure of the removal rate of surface atoms is the sputter yield Y, defined as the ratio between the number of sputter ejected species and the number of incident particles. Sputtering only occurs if the incident particles have enough energy to overcome the binding energy of the elements that constitute the material. In a deposition chamber under reduced pressure, a discharge is established between the cathode (target material from where the particles are ejected) and the anode (substrate onto which the coating will be formed). Usually there are three distinct phases in the sputtering process: (i) ejection of the target material; (ii) transport of the ejected material and (iii) nucleation and growth of the film. The control of several deposition parameters in each one of these three phases allow to a perfect control over the deposited thin film and obtaining tailor made materials, which are not predicted by conventional thermodynamics.

The ejection of the target material is achieved by simply momentum transfer between the ionic rare gas positive ions with the constituent material of the target. Argon is one of the most commonly used rare gases. It is an inert gas and therefore has the advantage of not change the chemistry of the target material by reacting with the ejected species. It has an atomic weight that guarantees the adequate sputtering of most of the chemical elements, has a low cost and high availability in the market, and can be purchased with high purity. In the course of the ionization inside the chamber, a plasma is formed which needs to be stable, in order for the process to proceed. In order to induce the plasma positive ions collision with the target, they must be accelerated by a negative potential. For this reason, the applied deposition power must be high, so that the ions can acquire sufficient energy to promote the ejection of secondary electrons from the target, contributing to the maintenance of plasma. The pressure in the deposition chamber needs to be well-controlled in order to promote a high number of collisions between the secondary electrons and the gas atoms, allowing ionization to proceed and ensure the maintenance of the plasma. However, it must not be too high, as in this case, argon ions will suffer too many collisions in their path, diminishing the free mean path, leading to loss of energy and arriving at the target with lower energy that the one needed to promote sputtering.

**2. Production of nanocomposites**

The use of composites is usually required when the materials or its surface must present a combination of properties/characteristics that are not possible to obtain from a single material. The materials for the matrix can be either organic, polymeric materials, or inorganic, such as ceramics and metals or metal alloys. In addition, the fillers can belong to these two classes of materials. When one of the dimensions of the filler is of nanometric scale, lower than 100 nm, it is called nanofiller and the resulting material a nanocomposite. The most commonly used inorganic nanofillers are carbides, nitrides, borides, oxides, metallic particles, clay, carbon nanotubes, nanodiamond and, more recently, graphene. Regarding the organic nanofillers, the most common, depending on the application, are polytetrafluoroethylene, nanocellulose fibers or cellulose nanocrystals. Nevertheless, some combinations of matrix and reinforcement are not able to be produced by conventional methods. In fact, the reinforcement of a metallic matrix with an organic nanofiller is forbidden, as the processing temperature of the metal material occurs at a temperature that completely degrades the organic filler. There are an extensive number of excellent reviews on the production of nanocomposites (see Refs. [3, 4] as

Hybrid Nanocomposites Produced by Sputtering: Interaction with Eukaryotic and Prokaryotic Cells

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**Figure 1.** Schematic representation of the nucleation and grow of a film deposited by sputtering.

examples) and some brief examples, based in these two references, are given.

can be used in combination with sputtering or electrodeposition.

posites have also been produced by this method.

The sol–gel method is suitable for obtaining nanocomposites coatings with a thickness up to 1 μm. However, the method presents several drawbacks, namely its application onto metallic substrates, crackability and not appropriate if a thermal treatment is required. This method

Chemical vapor deposition (CVD) method is usually used for the fabrication of inorganic/ inorganic nanocomposites coatings and, sometimes, in order to improve the quality of the coatings, the aerosol-assisted CVD can be used. Some organic (matrix)/inorganic nanocom-

Physical vapor deposition (PVD) technology includes evaporation and sputtering, among other less used technologies. It can be used for the production of hybrid nanocomposites and, especially sputtering, as described in the next point of this chapter, is one of the most versatile

for the production of a great combination of inorganic/organic nanocomposites.

If they have enough energy, the ejected particles from the target are transported through the plasma to the substrate, where they eventually deposit and form the coating. The trajectory of the ejected particles is random, in their direction, following a cosine law. The process of the formation of the coating can also be considered in three phases (**Figure 1**). In the first phase, the atoms ejected from the target transfer their kinetic energy to the substrate, becoming "adatoms," that is, nonbonded atoms. In the second phase, the adatoms diffuse superficially over the substrate where they either suffer desorption or are accommodated in a low surface energy location onto the substrate. Finally, the third phase takes place when the atoms readjust their position in the network by bulk diffusion processes.

The properties of the films deposited by this technique 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 these cases, the sputtering is said to occur in a reactive mode. The use of a magnetron associated with the cathode creates a magnetic field that imposes compulsory trajectories to the electrons ejected by the target, increasing the bombardment density.

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**Figure 1.** Schematic representation of the nucleation and grow of a film deposited by sputtering.
