Conductance oscillations in low-dimensional ion implanted regions annealed by rapid thermal annealing

We have investigated the Coulomb blockade in gate-controlled hopping conduction systems made up of small-dimensional focused ion beam (FIB) implanted wires having a small non-implanted gap. Dot structures are formed in the gap by potential fluctuations caused by dispersed Ga impurities and implantation-induced defects. In the present work, the samples were subjected to two thermal treatment methods: furnace annealing at 600 degrees C for 30 min and rapid thermal annealing (RTA) at 900 degrees C for 30 s. In both samples, the conductance oscillates by varying the gate voltage at low temperatures, in which the nearest-neighbor hopping conduction is dominant. In the samples annealed by RTA, the oscillation amplitude becomes much larger compared with that of samples annealed at 600 degrees C, which suggests that implantation-induced defects are annihilated by the thermal treatment at high temperatures. There coexist periodic and random peaks in the observed oscillation, which originate from the Coulomb blockade and hopping path changes, respectively. From obtained measurements, the dot size is estimated to be about 24 nm for the sample annealed at 600 degrees C and 14 nm for the sample annealed at 900 degrees C. The width of tunneling barrier of the sample annealed at 900 degrees C was estimated to be about 14-17 nm.