**1. Introduction**

The possibility of improving the surface properties of a material preserving the original properties of the bulk is a major interest in the application of thin films. In general, the purpose of coatings is to obtain films of high hardness and resistant to wear and corrosion deposited on the surface of metallic materials. A class of thin films that has been gaining prominence is that of nanocomposites thin films (NTFs) that in addition to the advantage allow the union of different materials whose combination of properties allows obtaining specific characteristics for use in each application [1–4].

The NTFs are widely applied in the automotive, chemical, aerospace, electronics, and biomedical industries due to their attractive properties such as high hardness, good tribological properties, excellent resistance to corrosion and oxidation at high temperatures [5–7].

An important fact to be observed is the synergism of the properties of nanocomposite materials. Often a monolithic thin film is not able to gather specific properties in isolation, and the complement of these properties can be obtained by inserting another type of material that presents the characteristics that were missing.

As an example, we can mention the Cr-C nanocomposite thin film that coats devices exposed to the action of seawater. C improves adhesion, toughness and

decreases surface roughness while Cr exhibits excellent anticorrosion properties [8]. Thus, we can note that the combination of elements Cr and C provides the obtaining of a thin film that brings together the best characteristics of the two elements.

There are several techniques for NTF growth. In general, these techniques are inserted in the following groups: (a) processes of physical vapor deposition (PVD) and (b) chemical vapor deposition (CVD) processes. In PVD processes, the material is converted to its vapor phase in a vacuum chamber and condensed on the substrate surface in the form of a thin film. In CVD processes, there is the spraying of the substance to be deposited, where the vapor is thermally decomposed into atoms and molecules, which can react with other gases, vapors, or liquids in order to produce a solid film on the substrate surface [9–12].

Some control parameters differentiate well the techniques belonging to these groups, which makes in many cases a technique more interesting or more appropriate than another. For example, in conventional CVD processes, the treatment temperature is high, while PVD processes occur at lower temperatures [13–15].

This chapter presents some techniques for NTF growth based on the processes of physical vapor deposition, chemical vapor deposition, and layer-by-layer technique. For each case the advantages, disadvantages and applications are mentioned. We hope that this brief chapter will encourage researchers to study the NTF in terms of improving their properties and in the knowledge or development of other thin films growth techniques.

### **2. Nanocomposites (thin films)**

The nanocomposites are multiphase solid materials obtained by insertion of nanoscale crystals dispersive in a second phase. The most common nanocrystals are based on hard phases such as transition metal nitrides and carbides. The second-phase materials usually present in two types: (a) the hard phase, where the nanocomposite exhibits ultrahardness, but demonstrates brittle failure at high loads; and (b) the soft phase, where the resulting nanocomposite has high hardness and a super-tough structure [8].

The ratio control of these phases allows the obtaining of nanocomposites whose properties of one of the phases complement those of the other phase resulting in materials that can be applied in several areas. In the field of coatings, NTFs arouse a lot of interest due to the various combinations of properties. In the next paragraphs, we will highlight some studies in NTF in terms of the properties obtained in each case.

Lakra et al. [16] carried out the fabrication and electrochemical characterization of cobalt oxide (Co3O4)/graphene nanosheets nanocomposite deposited on stainless steel substrates as efficient electrode for supercapacitor application. The supercapacitor can achieve a power density in the range of 0.3–0.8 kW/kg with energy density of 2.4–9.8 Wh/kg, and it shows good electrochemical stability with a loss of 5% in capacitance after 1000 cycles. For the authors, the performance of the device can be improved by optimizing appropriate concentration of CO3O4 and graphene in the nanocomposite. The better performance was attributed to the synergistic effect of graphene and CO3O4 in the composite.

Scharf et al. [17] analyzed the synthesis, structure, and friction behavior of titanium doped tungsten disulfide (Ti-WS2) nanocomposite solid lubricant thin films deposited on Si (100) substrates. The pure WS2 thin films show columnarplate morphologies with porosity between the plates, which leads to early fracture *Nanocomposites Thin Films: Manufacturing and Applications DOI: http://dx.doi.org/10.5772/intechopen.103961*

at room and high temperatures. With the addition of Ti, the room temperature friction coefficient measurements show some improvement when low amounts of Ti are added to WS2. This behavior was also identified for high-temperature (500°C) friction tests.

Dang et al. [18] studied the influence of Ag contents on structure and tribological properties of TiSiN-Ag nanocomposite coatings deposited on Ti-6Al-4V substrates. In this study, the authors observed that the variation of the Ag content directly influences the hardness, friction coefficient, and wear resistance. For low Ag content (1.4 at.%), the coating exhibited high hardness (36 GPa), but poor wear resistance. As the silver content increased from 5.3 to 8.7 at.%, the films exhibited small variation in hardness and greater layer homogeneity. A better performance in terms of wear resistance in artificial sea water was observed for a silver content of 5.3 at.%, while in ambient air, the wear resistance was higher for the coating with 7.9 at.% Ag. Further increasing the Ag content (21.0 at.%), there is a very large loss in hardness although possessing low friction coefficient both in ambient air and in artificial seawater.
