A possible road to 77 K single-electron devices

The application of single-electron devices is restricted to temperatures at which Coulomb blockade occurs. The most critical parameter of the devices is the tunnelling capacitance. Operation at liquid helium temperature, for example, requires tunnelling capacitances of the order of 20 aF. To realize such low capacitances, advanced electron-beam lithography below 20 nm is mandatory in fabrication schemes proposed up to now. Here we will present a new fabrication process that is capable of tunnelling capacitances as small as 1.5 aF with relaxed technological requirements at the same time. The detailed studies of Coulomb blockades at 20 K currently made may define the route to 77 K operation.