Long-range electron transport in Prussian blue analog nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Prussian blue analogs (PBAs) are versatile materials with tunable electronic properties.
• Nanoscale devices offer unique platforms for studying fundamental charge transport mechanisms.

Purpose of the Study:

• To investigate electron transport through single and multiple Prussian blue analog (PBA) nanocrystals.
• To determine the charge transport mechanism and identify mediating electronic orbitals.
• To analyze inter-nanocrystal coupling in multi-nanocrystal devices.

Main Methods:

• Fabrication of nano-scale devices using 1-3 PBA nanocrystals (CsCoFe and CsNiCr) contacted by conducting-AFM.
• Measurement of current-voltage characteristics and analysis of exponential length dependence.
• Theoretical analysis of current-voltage curves and comparison with ab initio calculations.

Main Results:

• Observed exponential current dependence on PBA nano-device length with low decay factors.
• Deduced electron transport mediated by localized d bands (Fe(ii)-t2g for CsCoFe, Ni(ii)-eg for CsNiCr) around 0.5 eV from the Fermi level.
• Consistent conductance values for multi-nanocrystal devices indicate multi-step coherent tunneling with strong inter-PBA coupling (0.1-0.25 eV).

Conclusions:

• Electron transport in PBA nanocrystals is governed by localized d-orbital mediated tunneling.
• Multi-nanocrystal devices exhibit coherent tunneling, suggesting potential for molecular electronic applications.
• Strong electrostatic coupling facilitates charge transport between adjacent PBA nanocrystals.