Coulomb blockade phenomena in Si metal-oxide-semiconductor field-effect transistors with nano-scale channels fabricated using focused-ion beam implantation

We have fabricated Si metal-oxide-semiconductor held-effect transistors of small dimensions using focused-ion-beam (FIB) implantation and SiO2 implantation masks with the width of 63-118 nm and have investigated the Coulomb blockade phenomena in these devices. The source and drain regions are formed by FIB implantation with a beam diameter of about 100 nm and the effective channel length is estimated to be 27-82 nm. Periodic oscillations of conductance, which are considered to be Coulomn blockade osillations, are observed at temperatures below 13 K. The measured oscillation period of V-G is 1.2-3.1 V and the gate capacitance is estimated to be 0.053-0.14aF for different channel lengths. Furthermore, it is found the the oscillation period of V-G increases as the channel length increases, which indicates that the dot radius decreases with increasing channel length. Large negative magnetoresistance is distinctly observed at the top of oscillation peaks and, on the other hand, only weak magnetoresistance is obtained at the bottoms.