*1.3.3 Pulsed Laser Deposition*

Thermal evaporation and Magnetron sputtering units having few limitations merely two to three composite materials deposited at prompt time. To overwhelmed constraint Laser ablation or PLD (schematic of PLD is shown in **Figure 10a**) had better established to be an unique furthermost suitable techniques for the deposition of thin films comprising an unpredictable through composite stoichiometry. Also PLD has some inimitable advantages such that in-situ temperature controller, partial pressure atmospheric condition, layer by layer coatings, varying the ablation rate exclusively to develop micro/ Nano structured thin film, even this system delivers sufficient microstructure variation and morphologies necessitate for superior electrochemical performance as the most important benefits in PLD are larger deposition rate, precise thickness control unit, capability to functioning in high reactive background gases pressures, and fewer nonconformity from the target composites [50]. The thin film fabrication process parameters of the PLD is exposed in **Table 2**. In this technique Krypton Fluorine (KrF) premixed laser source was used to ablate

#### **Figure 10.**

*(a) Schematic diagram of PLD coating unit; (b) photographical image representation for "laser plume" at CSIR-CECRI India (Reprinted with permission from Ref. [28]. Copyright 2020 Royal Society of Chemistry).*


#### **Table 2.**

*Thin film fabrication process parameters in pulsed laser deposition (PLD).*

target of the materials in a high vacuum pressure up to 10−7 mbar with the help of turbo molecular pump. The laser excimer emits the laser pulse energy 0.8 joule/ pulse at a wavelength 248 nm uses high power (40 W) laser pulses to melt, and evaporate and ionize material from the surface of a target. This laser ablation event produces a high plasma plume that magnify intensely ahead of the target surface, and the produced laser plume is shown in **Figure 10b**. Additionally, PLD unit having rotating target carousel is used to make larger composite materials film in an ambient vacuum condition. PLD is used to fabricate all metals (Au, Pt, Ni, Ag, Cu, Al, etc.), metal oxides (MnO2, V2O5, Co3O4, NiO, SnO2 etc.), metal sulfides (MoS2, CoS, NiS, FeS and VS2 etc.), metal nitrides (CrN, TiN, VN and BN), conducting polymers (PANI, PPy etc.), solid state polymers (LIPON etc.) and other metalloid compound thin films for countless applications. While PLD is the stoichiometric conversion of the ablated material on or after the target directed to the substrates and the crystallite phase of the subsequent film is not essentially the similar that the target of materials.

From these consequences PLD is one of the ideal candidates to form micro / Nano structured films for energy storage and energy saving applications. Recently, de Krol et al. fabricated BiVO4 thin film prepared by PLD for solar water splitting application [51]. Wang et al. investigated supercapacitor performances of NiSe thin film electrodes fabricated by PLD technique and the corresponding electrodes delivered specific capacitance value 696 F g−1 [52]. Patil et.al studied effect of temperature of CoFe2O4 thin film prepared via PLD for supercapacitor studies [53]. This work CoFe2O thin film annealed at 450°C electrode exhibited 777 F g−1. Julien et al. examined Li2TiO3 thin film electrodes produced by PLD aimed at energy storage application. Here the LTO thin film grown at 600°C delivered a specific discharge capacity of 46 μAh cm−2 [54]. Lastly Author group demonstrated WO3 and V2O5 symmetric thin film supercapacitors and Supercapbattery device assembled by using in-situ annealed thin film electrodes prepared by PLD. Thin flexible Supercapbattery device presented superior charge storage performance, also the device displayed high volumetric capacitance about 40 F cm−3 [28]. As a final point, PLD is the most appropriate technique for energy storage device fabrication.

#### **1.4 Current electrode materials for thin film energy storage**

Current commercial flexible energy storage system contains anode and cathode are regularly exclusive based on the intercalation/ deintercalation principal of potassium or lithium ions. Even though these flexible energy storage system by now exhibit a greatly upgraded when compared to the conventional supercapacitors of 10 years ago, their energy storage mechanism principle is also subject to essential limitations

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

prominent to comparably low energy storage system densities. One of the challenging application for supercapbatteries in terms of specific energy and power densities in future portable Micro-electronics. Transition metal oxides such as RuO2, Fe2O3, Co3O4, WO3, V2O5, NiO, Bi2O3 etc., and ternary metal oxides NiCo2O4, ZnCo2O4, NiMoO4, ZnWO4 etc., have long been disregarded as possible electrode materials for all kinds of energy storage system such as Lithium ion batteries, Supercapacitors and Supercapbatteries because of the they having high pore volume with high crystalline nature for insertion / deinsertion of electrolytic ions. The positive electrode as the cathode, the positive electrode frequently has a superior potential than the negative electrode (Anode). The current always streams from the positive electrode to the negative electrode via the peripheral circuit, and the electrons movement in the opposite way. However, cathode (positive) and anode (negative) are well-defined, by the electrochemical electrode reaction being reduction or oxidation.

#### *1.4.1 Anodic materials*

For fabrication of hybrid energy storages such as ASCs and Supercapbatteries, anodic materials are promising candidate to meet future energy demands. Usually anodic materials charges stored through an electrolytic ions intercalation/ deintercalation mechanism. As a result, the rate capability performance of hybrid EES is restricted by the sluggish kinetics of ion diffusion in the solid surface, as the surface adsorption–desorption approaches at the cathodic materials are noticeably more rapidly than the Faradaic reactions occurs at the anode, More than a few materials, Bi2O3, MoO3, Fe2O3, VN and WO3 are being investigated as the suitable anodes to fabricate hybrid EES because they are having high theoretical specific capacity, faster ions diffusion and easily allowing to intercalation of electrolytic ions.
