**4.1 Indium oxide based nanostructured thin films**

IO based nanostructured thin films are immensely important due to their excellent optical, electrical, and mechanical properties suitable for various applications like energy conversion, biological and chemical sensing, solar cells, thin film transistors etc. [34–45]. Structural, optical, magnetic and electrical properties of IO based nanostructured thin films are discussed in the next sub-sections.

It is well known that IO based nanostructured thin films can act as excellent n-type transparent conducting oxides (TCOs) [34–45]. In bcc-Sn doped In2O3 forming ITO, the low formation energy implies a greater abundance of both the neutral and the cationic states of Sn dopant [38]. The structures of the thin films as confirmed by X-ray diffraction study, indicate that the films are polycrystalline with bcc structure having a 100 intensity peak at (222) plane of the crystal lattice. It is observed that the mobility of atoms and clusters on the surface of a substrate is proportional to their energy that would increase with increasing curing temperature. This would lead to the growth of In2O3 crystallites along a crystal plane (100). Among the fabricated IO based thin films, ITO is the most widely used efficient TCO due to its low energy of defect formation towards enhancing greater electrical properties [34–45]. It is worthy to note that the optical properties of IO based thin films are primarily dependent upon post annealing temperature, film microstructure, film physical thickness, surface roughness, levels of impurities, defect (like oxygen vacancies) concentration and deposition parameters [16, 17, 34–45, 59]. Low absorption (0.04–1.10%) of incident light in visible region is a crucial factor for IO based TCOs. The optical band gap widening or narrowing of IO based films occurs also based on dopant concentration [34]. In this context, different values as obtained from the reported works on IO based thin films show a high optical transparency (82–93%) of the films [34–45]. On the other hand, it is very much important to achieve the magnetic properties of IO or IO based thin films and bulk nanomaterials. In order to obtain the magnetic properties of these nanomaterials different magnetic metal such as Cr, Mn, Fe, Co, etc. ions with variable oxidation states are generally doped into the metal oxide [59]. It is found that the magnetic

*Indium Oxide Based Nanomaterials: Fabrication Strategies, Properties, Applications, Challenges… DOI: http://dx.doi.org/10.5772/intechopen.94743*

property is induced in indium oxide due to the presence of oxygen vacancies. The property basically depends on the nature/concentration of external dopant [59, 60].
