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

We have investigated the Coulomb blockade in gate-controlled hopping conduc tion systems made up of small-dimensional focused ion beam (FIB) implanted wires having a small non-implanted gap. Dot structures are formed in the ga p by potential fluctuations caused by dispersed Ga impurities and implantat ion-induced defects. In the present work, the samples were subjected to two thermal treatment methods: furnace annealing at 600 degrees C for 30 min a nd rapid thermal annealing (RTA) at 900 degrees C for 30 s. In both samples , the conductance oscillates by varying the gate voltage at low temperature s, in which the nearest-neighbor hopping conduction is dominant. In the sam ples annealed by RTA, the oscillation amplitude becomes much larger compare d with that of samples annealed at 600 degrees C, which suggests that impla ntation-induced defects are annihilated by the thermal treatment at high te mperatures. There coexist periodic and random peaks in the observed oscilla tion, which originate from the Coulomb blockade and hopping path changes, r espectively. From obtained measurements, the dot size is estimated to be ab out 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 an nealed at 900 degrees C was estimated to be about 14-17 nm.