Ferritin-Based Single-Electron Devices

Abstract

We report on the fabrication of single-electron devices based on horse-spleen ferritin particles. At low temperatures the current vs. voltage characteristics are stable, enabling the acquisition of reproducible data that establishes the Coulomb blockade as the main transport mechanism through them. Excellent agreement between the experimental data and the Coulomb blockade theory is demonstrated. Single-electron charge transport in ferritin, thus, establishes a route for further characterization of their, e.g., magnetic, properties down to the single-particle level, with prospects for electronic and medical applications.

Keywords: Coulomb blockade; ferritin; nanoelectronics; single-electron transport.

Figure 1

(a) Schematic representation of ferritin, based on the protein data base (PDB) of horse-spleen apoferritin (PDB ID: 2W0O [29]). The organic shell is in green; the mineral core occupying the internal cavity is in red. (b) Schematic circuit of a device containing one ferritin particle. (c) Electrical characterization of device A1 before (grey curve) and after (green curve) ferritin deposition, measured at room temperature, in vacuum. The grey curve indicates an open circuit, reflecting an empty device. The increase in current shown in the green curve indicates the capture of ferritin. In both cases, the current is measured by sweeping the voltage from negative to positive values, followed by sweeping from positive to negative values. (d) Scanning electron microscopy image of an empty device showing the gap of 9–19 nm size between source and drain electrodes.

Figure 2

Experimental current-voltage (IV) characteristics (colored dots) and the corresponding calculated curves using the orthodox Coulomb blockade model (black dashed lines) acquired on four devices, displaying clear step-like features (light blue dots) or a single transport gap centered around zero bias (green dots). (a,e,g) Experimental IVs measured on, respectively, device D2, E1, and D1; obtained by sweeping the voltage from positive to negative values. (c) IV measured on device I1, obtained by sweeping the voltage from negative to positive values. The corresponding differential conductance is depicted in figures (b,d,f,h). The data were recorded at either 4.2 or 5.0 K. The parameters used for the simulations are presented in Table 1.

Figure 3

Experimental current-voltage characteristics acquired on device A1, at two different temperatures. (a) Data measured at 4.2 K (light blue dots). (b) Data acquired at 22 K (orange dots). The black dashed lines indicate the calculated curves using the orthodox Coulomb blockade model with parameters: $C_1=28$ aF, $C_2=34.7$ aF, $R_1=0.4$ M$\mathsf{\Omega }$, $R_2=0.08$ G$\mathsf{\Omega }$, $Q_0=0.15$ e.

Figure 4

Total capacitances ($C=C_1+C_2$) and total resistances ($R=R_1+R_2$) calculated with the orthodox Coulomb blockade model for the 22 devices showing Coulomb-blockade at temperatures below 100 K. Table S1 contains the entire set of Coulomb blockade parameters used to model each device, at the lowest recorded temperature. (a) Total capacitance histogram. (b) Total resistance histogram. (c) Total capacitance plotted against the total resistance.