**8. Conclusions**

This chapter attempted to carry out the study of thin films maintaining a tight correlation among the deposition techniques, the resulting microstructure, and their physical properties. It was found that the development of deposition methods are driven to satisfy the needs for films with specific mechanical, physical and chemical properties. Overall, they have evolved to enable the fabrication of thin films with increasingly higher purity, based on a variety of depositing materials and substrates with high reproducibility. However, the cost of material processing of certain structures such as nanostructures, quantum well, quantum wires, and quantum dots is still a challenge for commercial applications. The selected deposition technique and deposition parameters greatly define the final thin film microstructure being either amorphous, polycrystalline or epitaxial. In particular, the deposition temperature and deposition rate strongly influence the adatom-diffusion at the substrate surface giving rise to the formation of islands whose sizes increase with feeding of atoms. The most common morphological feature in many films is a columnar structure formed due to the feeding of atoms from the vapour flux once the adatom-diffusion in the substrate surface has placated due to the interfering process between islands. The mechanical, electrical, and optical properties of thin films are determined by the final morphology. It is important to remark that these properties normally deviate from the values corresponding to their bulk counterparts. For example, the yield strength and hardness are higher in thin films due to the influence of crystallite size, and movement of dislocations usually found in thin films. Likewise, the electrical conductivity is also affected by additional scattering mechanisms appearing due to the reduced film thickness. There are several techniques available for thin film characterization, but their accuracy strongly depends on the depositing material, substrate material, and film thickness. In most cases, two or more techniques are complementary used to access the required information with high precision. Regardless of the progress in thin film technology, important challenges remain to be tackled, including the accurate prediction of film properties based on the final microstructure, more advanced characterization techniques in the biomedicine field, and sophisticated models for data analysis.
