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Enhanced electrical properties in sub-10-nm WO3 nanoflakes prepared via a two-step sol-gel-exfoliation method.

Zhuiykov S, Kats E - Nanoscale Res Lett (2014)

Bottom Line: The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 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 techniques.CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method.It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Materials Science and Engineering Division, CSIRO, 37 Graham Road, Highett, VIC 3190, Australia.

ABSTRACT
The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 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 techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures.

No MeSH data available.


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The topography and morphology of ultra-thin exfoliated Q2D WO3. AFM images of two exfoliated Q2D WO3 nanoflakes (flakes 1 and 2) sintered at 550°C (A), 3D image (B), cross-section height measurements of flake 1 (C) and flake 2 (D) and depth histogram for flake 2 (E).
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Figure 3: The topography and morphology of ultra-thin exfoliated Q2D WO3. AFM images of two exfoliated Q2D WO3 nanoflakes (flakes 1 and 2) sintered at 550°C (A), 3D image (B), cross-section height measurements of flake 1 (C) and flake 2 (D) and depth histogram for flake 2 (E).

Mentions: The topography and morphology of ultra-thin exfoliated Q2D WO3 sintered at 550°C and their characteristics analysed by CSFS-AFM are presented in Figure 3. CSFS-AFM is a relatively new technique for mapping the electrical properties of the developed Q2D nanostructures. Therefore, AFM with Peak Force TUNA™ module was employed to study the topography and morphology of Q2D WO3 nanoflakes. Multiple flake morphology of Q2D WO3 (Figure 3A) is evidently and consistently observed in all images on the analysing image surface area of 18,365.3 nm2. The measured surface area difference was 18.2%. Figure 3B demonstrates 3D image of the general profile and provides information in relation to the structure of two adjacent Q2D WO3 flakes with their measured thickness in the range of 7 to 9 nm (Figure 3C,D). It was confirmed that the mechanical exfoliation enables the development of uniformed nanostructure of ultra-thin Q2D WO3 nanoflakes with the average determined dimensions of 60 to 80 nm in length and 50- to 60-nm wide. The depth histogram, depicted in Figure 3E, displays the coherency in the structure of the nanoflake. The increased Fowler-Nordheim tunnelling current at the edges between the different nanoflakes represented the dark areas on the image (Figure 3B). This indicates local structural thinning of the oxide during the fabrication, which serves as an insulating area between adjacent active regions. Enhanced current flow is noticeable along the grain boundaries of WO3 nanoflake, the peak current with maximum intensity was clearly identified and its measured value was 248 pA. The average tunnelling current was relatively low, corresponding to the changes in WO3 nanoflake thickness and small inhomogeneities, as each of the developed Q2D WO3 nanoflake consisted of several fundamental layers of WO3. Due to the low conductivity of the fabricated Q2D WO3 nanoflakes, the adhesion between the PF TUNA tip and the WO3 nanoflakes was found to be poor. Noteworthy, the measured thickness of exfoliated Q2D WO3 nanoflakes sintered at 650°C was about 15 to 25 nm which is thicker than those exfoliated Q2D WO3 nanoflakes sintered at 550°C.


Enhanced electrical properties in sub-10-nm WO3 nanoflakes prepared via a two-step sol-gel-exfoliation method.

Zhuiykov S, Kats E - Nanoscale Res Lett (2014)

The topography and morphology of ultra-thin exfoliated Q2D WO3. AFM images of two exfoliated Q2D WO3 nanoflakes (flakes 1 and 2) sintered at 550°C (A), 3D image (B), cross-section height measurements of flake 1 (C) and flake 2 (D) and depth histogram for flake 2 (E).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150682&req=5

Figure 3: The topography and morphology of ultra-thin exfoliated Q2D WO3. AFM images of two exfoliated Q2D WO3 nanoflakes (flakes 1 and 2) sintered at 550°C (A), 3D image (B), cross-section height measurements of flake 1 (C) and flake 2 (D) and depth histogram for flake 2 (E).
Mentions: The topography and morphology of ultra-thin exfoliated Q2D WO3 sintered at 550°C and their characteristics analysed by CSFS-AFM are presented in Figure 3. CSFS-AFM is a relatively new technique for mapping the electrical properties of the developed Q2D nanostructures. Therefore, AFM with Peak Force TUNA™ module was employed to study the topography and morphology of Q2D WO3 nanoflakes. Multiple flake morphology of Q2D WO3 (Figure 3A) is evidently and consistently observed in all images on the analysing image surface area of 18,365.3 nm2. The measured surface area difference was 18.2%. Figure 3B demonstrates 3D image of the general profile and provides information in relation to the structure of two adjacent Q2D WO3 flakes with their measured thickness in the range of 7 to 9 nm (Figure 3C,D). It was confirmed that the mechanical exfoliation enables the development of uniformed nanostructure of ultra-thin Q2D WO3 nanoflakes with the average determined dimensions of 60 to 80 nm in length and 50- to 60-nm wide. The depth histogram, depicted in Figure 3E, displays the coherency in the structure of the nanoflake. The increased Fowler-Nordheim tunnelling current at the edges between the different nanoflakes represented the dark areas on the image (Figure 3B). This indicates local structural thinning of the oxide during the fabrication, which serves as an insulating area between adjacent active regions. Enhanced current flow is noticeable along the grain boundaries of WO3 nanoflake, the peak current with maximum intensity was clearly identified and its measured value was 248 pA. The average tunnelling current was relatively low, corresponding to the changes in WO3 nanoflake thickness and small inhomogeneities, as each of the developed Q2D WO3 nanoflake consisted of several fundamental layers of WO3. Due to the low conductivity of the fabricated Q2D WO3 nanoflakes, the adhesion between the PF TUNA tip and the WO3 nanoflakes was found to be poor. Noteworthy, the measured thickness of exfoliated Q2D WO3 nanoflakes sintered at 650°C was about 15 to 25 nm which is thicker than those exfoliated Q2D WO3 nanoflakes sintered at 550°C.

Bottom Line: The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 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 techniques.CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method.It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Materials Science and Engineering Division, CSIRO, 37 Graham Road, Highett, VIC 3190, Australia.

ABSTRACT
The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 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 techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures.

No MeSH data available.


Related in: MedlinePlus