Single-electron charging effects in one-dimensional arrays of ultrasmall tunnel junctions

Coulomb blockade of single-electron tunneling and high sensitivity to an external electric field has been observed for 1D series arrays of ultra-small-area (<0.1×0.1 μ${\mathrm{m}}^2$) tunnel junctions, made of Al/${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{O}}_{\mathrm{y}}$/Al, at helium temperatures. In particular, the dc voltage V across the array responds strongly to a voltage $U_g$ applied to a control electrode. For an array of thirteen junctions, the voltage gain $K_V$=‖δV/δ$U_g$‖ of the resulting sub-single-electron- transistors reached 0.2, while the charge sensitivity of the device was as high as 2×${10}^{\mathrm{-}4}$e/${\mathrm{Hz}}^{1/2}$ at a frequency f=10 Hz.