Mechanically exfoliated ultra-thin WO3 nanostructures: study of their enhanced electrical properties

Ultra-thin orthorhombic β-WO 3 nanoflakes were prepared by two-step sol-gel-exfoliation method and sintered at 550 and 650 °C, respectively. Their morphology and electrical properties were investigated by the following material characterisation techniques: energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy. CSFS-AFM analysis exhibited good correlation between the topography of the developed nanostructures and various features of WO 3 nanoflakes. It was found that β-WO 3 nanoflakes annealed at 550 °C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, microstructured and nanostructured WO 3 synthesized at alternative temperatures.