Electrically Tunable Resistance of a Metal

Electric field-induced tuning of material properties is usually restricted to nonmetals such as semiconductors and piezoelectric ceramics. We show that variations of the electrical resistance of a metal (Pt) in the range of several percent can be reversibly induced at low charging voltages making use of a nanocrystallite-electrolyte composite. The charge-induced resistance variation is analyzed taking into account the modification of the charge carrier density and scattering rate by surface charging. The contribution arising from the charge-induced variation of the lattice constant is found to be small.

Figure 1

Electrochemical cell for resistance measurement on porous nanocrystalline Pt by means of 4-point method in dependence of charging by double-layer formation. WE, CE, RE: working, counter, and reference electrode, respectively.

Figure 2

Variation of the electric resistance $R$ of porous nanocrystalline Pt upon charging with a voltage $U$ using (a) 1-molar KCl or (b) 1-molar KOH as the electrolyte. The arrows indicate the direction of charging.

Figure 3

Relative variation $\Delta R/R$ of the electric resistance of porous nanocrystalline Pt with the imposed specific charge density $\Delta q$ using KCl as electrolyte with different $p\mathrm{H}$ values: 1 M KCl with 0.01-molar KOH ($p\mathrm{H}$ 12, □, ■), with 0.01-molar HCl ($p\mathrm{H}2$, ●, ○), or with a buffer solution of 0.01-molar ${\mathrm{KH}}_2{\mathrm{PO}}_4$ and 0.01-molar ${\mathrm{Na}}_2{\mathrm{HPO}}_4\times {\mathrm{H}}_2\mathrm{O}$ ($p\mathrm{H}$ 7, △, ▲). Filled and empty symbols refer to charging in positive and negative direction, respectively. The point of zero charging ($\Delta q=0$) was arbitrarily chosen at zero voltage.