**1.3 Why PVD techniques for flexible energy storage fabrication**

In the past few years ago EES device assembling electrodes such as anodes and cathodes fabrication frequently used approaches like Slurry, Hydrothermal and other synthesis methods ensuring sufficient draw backs for instance the active materials should be very high, low stability owing to require for proper binder, bulky electrodes may not appropriate for micro electronic device fabrication, larger size EES devices, essential proper complex mixture of active materials. To overwhelmed these scenario flexible thin film electrodes fulfill due to less active materials necessary for fabrication for instance compared bulky electrodes 2 to 10 μm thickness thin film electrodes fabrication required active mass of 0.2 to 1 mg, in attendance no necessity of binder required flexible thin film electrode fabrication because thin film electrodes are highly adhesive in nature. Thin film electrodes capable of assembling any miniaturized energy storage devices such as planar Micro- Nano supercapacitors and fiber based energy storages. Intended for emerging flexible thin film energy storage devices, there are numerous thin films coating methods for the occasion of Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), spray coatings, Electrochemical Deposition (ED) and liberal coating methods such as Atomic Layer Deposition (ALD) and Pulsed Laser Deposition (PLD) have been employed in the noticeable appearance of thin flexible electrode fabrications. Frequently, the expansion of micro and nanostructure coatings in thin film form are more suitable for flexible device applications and the major improvement for the thin film electrode is binder and conductive free in its architecture. As we identify that together with the different physical vapor deposition (PVD) techniques such as Thermal evaporation, e-beam evaporation, Magnetron sputtering and PLD, in predominantly PLD is matchless for the intention that its competency to functioning in very high pressure of background reactive gases. The recompenses of the PLD process are flexibility, fine *Physicochemical Approaches for Thin Film Energy Storage Devices through PVD Techniques DOI: http://dx.doi.org/10.5772/intechopen.99473*

thickness control, high growth rate, quick evaporation and compatible vaporization. PLD also plays an enthusiastic role in influencing the microstructure and phases of the numerous active TMOs and metal sulfides based electrode materials used in the electrode assemblies. In summary, thin film electrode fabrication by PVD techniques are most promising tool to enhance the materials crystalline nature, providing better nano structure with good adhesive properties than films prepared by other techniques.

#### *1.3.1 Thermal Evaporation*

Thermal evaporation coating system is a modest technique among all PVD system for thin film fabrication. The schematic diagram of thermal evaporation technique is displayed in **Figure 2a**. In this technique molten material in the form of powder, foils, pellets and salts for thin film fabrication with the help of boats, crucibles and buckets. Usually boats and crucibles made up of molybdenum and tungsten metals owing to they have high meting points. Thermal evaporation technique functioning under the principle of law of conservation such that electrical energy converted to the thermal energy, meanwhile molten materials transferred to one state to another state. Intended for deposition process occurs while applying the current through the boats or crucibles molten material at a particular temperature it goes condensation state to deposit in the form of solid state film on the substrate. In this thermal evaporation technique for a thin film deposition normally used molten material such as some metals foils Al, Cu, Ni, etc. and some metal oxides those materials having low melting points. Recently yen lei et.al approached thermal evaporation technique to form SnS2 thin film for flexible photodetector applications. Ziran Ye et al. reported Ag film on the liquid surface by using thermal evaporation technique for Surface Enhanced Raman scattering (SERS) application [44]. Hailin Hu et al. fabricated Zinc oxide thin film by using this method for Planar Perovskite Solar Cell application [45]. Author group reported V2O5 thin film supercapacitor prepared by thermal evaporation technique [46]. In conclusion, from the literature thermal evaporation technique is one of the simplest techniques for thin film fabrication for multiple applications also the suitable candidate for thin film energy storage fabrication.

#### *1.3.2 Magnetron sputtering*

Thermal evaporation technique has temperature limitation with deposition occurs only for materials having melting point below 1200°C. To overcome this issue Magnetron Sputtering (Schematic diagram is shown in **Figure 9**) coating unit as suitable PVD technique for thin film fabrication attributable to its ensuring more or less special features such as temperature limitations depending on the melting point, thickness control coating unit, easy way to deposit metals, semiconducting materials, ceramic materials and some polymers. In thermal evaporation technique composite thin films cannot be deposition at instant time as it depends on melting point deposition occurs sequentially, In contrast Magnetron sputtering Composite materials deposition happens for instantaneous due to its having multiple target (cathodes) holders. The deposition due to influence of ion bombardment of growing films intensely inspirations their microstructure, and for that reason their physical properties of the film should be changed. Ion bombardment may perhaps intensification to the movement of atoms on the surface of growing film, which effects in increasing the reordering probability of atoms. The thin film process parameters of the magnetron sputtering while deposition is displayed the **Table 1**. All metal oxides, metal sulfides, metal nitrides and metal alloy

#### **Figure 9.**

*Schematic diagram of magnetron sputtering unit.*


#### **Table 1.**

*Thin film preparation parameters of magnetron sputtering coating unit.*

composites materials based thin films by the promising method to deposit magnetron sputtering for innumerable applications, in particularly more than a few reports available based on energy storage applications. Hyunsik Im et al. reported CuO2 thin film fabricated by using magnetron sputtering for supercapacitor and electro catalyst [47]. Z. Zhang et al. stated molybdenum oxide thin film fabricated via magnetron sputtering for micro supercapacitor application [48]. Zhoucheng Wang et al. demonstrated CrN symmetric thin film supercapacitor with the help of magnetron sputtering unit, and the symmetric device exhibited excellent cycling stability [49]. Zhoucheng Wang et al. studied binder-free titanium nitride thin film electrodes prepared by magnetron sputtering unit for supercapacitors [20]. From the literature magnetron sputtering technology is one of advanced coating system even if comparable lot advantages than thermal evaporation technique, and magnetron sputtering is situated promising tool for flexible thin film electrode fabrications.

*Physicochemical Approaches for Thin Film Energy Storage Devices through PVD Techniques DOI: http://dx.doi.org/10.5772/intechopen.99473*
