In situ CdS nanocluster formation on scanning tunneling microscopy tips for reliable single-electron tunneling at room temperature

We report on a chemical approach to fabricating double-barrier tunneling junction (DBTJ) for room-temperature single-electron tunneling studies, by which CdS nanoclusters were directly synthesized on a scanning tunneling microscopy (STM) tip through an organic self-assembled monolayer (SAM) and in situ chemical reaction. The SAM/CdS-modified STM tip directly establishes a DBTJ structure with highly oriented pyrolytic graphite substrate with STM-based current-voltage measurement. Clear Coulomb staircases were observed at room temperature with this experimental approach, and the reproducibility was nearly 90%. When gradually reducing the tip-substrate gap by increasing the setpoint current, the staircase width showed a gradual decrease from 320 to 180 mV. These phenomena are well described by semiclassical model for correlated single-electron tunneling. (C) 1999 American Institute of Physics. [S0003-6951(99)00945-6].