Efficient field emission from α-Fe2O3 nanoflakes on an atomic force microscope tip

Abstract

Aligned arrays of flake-shaped hematite $\left(\alpha \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ nanostructure have been fabricated on an atomic force microscope (AFM) tip. They are created by simply heating an iron-coated AFM tip in ambience on a hot plate. These nanoflakes are characterized as $\alpha \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ single crystalline structures with tip radii as small as several nanometers and are highly effective as electron field emitters. With a vacuum gap of about $150\mu \mathrm{m}$ , field emission measurements of $\alpha \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ nanoflakes on AFM tips show a low turn-on voltage of about $400–600\mathrm{V}$ and a high current density of $1.6\mathrm{A}{\mathrm{cm}}^{-2}$ under $900\mathrm{V}$ . Such high emission current density is attributed to the nanoscale sharp tips of the as-grown nanoflakes. Based on the Fowler–Nordheim theory, it is demonstrated the enhancement factor of $\alpha \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ nanoflakes on AFM tips is comparable to that of carbon nanotubes. Our findings suggest that $\alpha \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ nanoflakes are potentially useful as candidates for future electron field emission devices.