A single-electron transistor and an even-odd effect in chemically synthesized Ge nanowires

Single-electron transistors have been fabricated with individual n-type monocrystalline germanium nanowires to realize an electron single-spin in a quantum dot. At low temperatures, well-pronounced Coulomb oscillations, with almost equidistant peak spacings and strongly varied peak amplitudes, were observed in a wide range of the back-gate voltage (Vg). The charge-stability diagram showed almost identical diamond-shaped dimensions and the charging energy turned out to be 110 μeV. In some Vg range, the two-electron periodicity in the addition energy was found, indicating the even-odd effect due to an alternate change of electron spin between 0 and 1/2. This work suggests the possible application to an electron-spin quantum-bit even with many electrons residing in the dot.