C) and (iii) at 873K (600 o C). The growths of the nanostructures were carried out for 1200 puls- es i.e. 120 seconds (2 minutes) and for 12000 pulses i.e. 1200 seconds (20 minutes). The samples were allowed to cool down inside the chamber naturally in the respective gas at- mosphere. The structure morphology analysis was carried out using scanning electron microscopy. Structural properties were performed through XRD analysis. The optical properties were studied using UVspectroscopy analysis. The electrical parameters such as conductivity, mobility and resistivity were evaluated using the Hall measurement setup. Finally, the thin film device current-voltage characteristics were carried out to study the switching performance. III. RESULTS AND DISCUSSIONS A. Surface morphology The colour of the MoO 3 thin films is bright shiny bronze whereas the colour of the MoO 2 films is dark coffee brown. This colouring phenomenon is due to the coalescence of the nanoparticles. M.A. Camacho-Lopez, Garcia and McCarron III have also reported the brown colour in the presence of argon gas for amorphous MoO 2 sputtered films. B. Structural morphology Figure 2 shows the FESEM images of the pulsed laser depos- ited various molybdenum oxide thin films. Figure 2ashows the sample deposited at 450 o C and using O 2 gas atmosphere, near the edges and unfilled region, hexagonal (100) nanorods, along with neatly arranged orthorhombic (040) structures of molybdenum trioxide (MoO 3 ) is observed. Figure 2bshows the sample deposited at 450 o C, using O 2 gas atmosphere, uni- formly arranged orthorhombic (040) structures of MoO 3 seen. Figure 2cshows the sample deposited at 450 o Cunder Ar gas atmosphere, near the unfilled region, neatly arranged mono- clinic structures of molybdenum dioxides (MoO 2 ) seen.Figure 2d represents the sample deposited at 450 o C using Ar gas atmosphere, uniformly arranged monoclinic structures of MoO 2 .Figure 2e represents the sample deposited at 600 o C and using O 2 gas atmosphere, near the unfilled region, neatly ar- ranged orthorhombic structures of molybdenum trioxides (MoO 3 ) is observed. Figure 2fshows the sample at 600 o C us- ing O 2 gas atmosphere, uniformly arranged monoclinic struc- tures of MoO 3 is seen. From the cross-section, the thickness of the film is measured to be approximately 500 nm. (a) (b)
ICDCS-2018 Figure 2. Field Emission Scanning Electron Microscopy (FESEM) images of Molybdenum oxides thin films deposited by pulsed laser deposition C. XRD analysis Figure 3. XRD spectra of pulsed laser deposited Orthorhombic MoO 3 and monoclinic MoO 2 thin films prepared at various deposition conditions
ICDCS-2018 Figure 4 Monoclinic MoO 2 thin film confirmed with ICSD & JCPDS data Figure 3 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.
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- Fall '12