Effect of size on the Coulomb staircase phenomenon in metal nanocrystals

The Coulomb staircase in polymer-covered Pd and Au nanocrystals of varying diameters in the 1.7–6.4 nm has been investigated by employing tunneling conductance measurements. Charging up to several electrons is observed at room temperature in the I–V data. Small nanocrystals show charging steps exceeding 200 mV while the larger ones exhibit smaller steps. Significantly, the charging energies follow a scaling law of the form, U=A+B/d, where d is the diameter of the nanocrystal. Furthermore, the line widths in the derivative spectra also vary inversely with the diameter.