**4.2 Investigation of MoO3 and MoO2 nanostructures**

**Figure 6** shows the FESEM images of the pulsed laser deposited with various thin film of molybdenum oxide. The sample deposited at 450 °C and using the O2 gas atmosphere, near the edges and unfilled region, hexagonal (100) nanotubes, along with neatly arranged orthorhombic (040) molybdenum trioxide (MoO3) structures is shown in **Figure 6a**. Followed with **Figure 6b** shows the sample deposited at 450 °C using the O2 gas atmosphere, uniformly arranged orthorhombic (040) structures of the MoO3 seen. Then, **Figure 6c** shows the sample stored at


**Table 3.** *Bandgap energy obtained from Tauc plot of optical transmittance.*

**Figure 6.**

*Field Emission Scanning Electron Microscopy (FESEM) images of molybdenum oxides thin films deposited by PLD. (a) and (b) MoO3 at 450* °C *(c) and (d) MoO2 at 450* °C*.*

450 °C under the argon gas atmosphere, near the unfilled region, neatly arranged monoclinic molybdenum dioxide (MoO2) structures. Finally, the sample deposited at 450 °C using the argon gas atmosphere, which shows uniformly arranged monoclinic MoO2 structures is shown in **Figure 6d** [10].

**Figure 7** shows the XRD spectra of the pulsed laser deposited molybdenum oxide thin films at the various conditions. The sample deposited at the room temperature was the as-deposited thin film which exhibits the amorphous nature. Then the sample was deposited at a substrate temperature of 450 °C and 600 °C, which exhibit orthorhombic structure with 020 and 040 peaks and are confirmed with the ICSD 80577. Then the deposition duration was increased from 2 minutes to 20 minutes, with the O2 atmosphere, which results in orthorhombic structures and hexagonal structures and the peaks are found at 100 and 211 respectively. Then the next sample when deposited with same temperature and duration under the Ar atmosphere, the XRD spectra shows the monoclinic structures and confirms as in **Figure 4** the presence of MoO2 with 110, 020 and 220 peaks with the ICSD 23722 and JCPDS 65–5787. When the sample deposition temperature increased from 450 °C to 600 °C, the structure crystallization takes place [11].
