Synthesis of ultra-small Si nano particle colloids and thin films-high temperature single electronics

We describe a procedure for dispersing electrochemical etched silicon into a colloid of ultra-small (∼1 nm) silicon nano particles. The particles are then reconstituted on a Si substrate by gentle evaporation from a volatile colloid, forming thin films. When the colloid or the film is excited with UV radiation at 355 nm, strong blue emission band at 390 nm is observable with the naked eye in room light. Two-terminal I-V spectra of the deposited film, taken using a scanning tunneling microscope (STM), show a single regular conductance resonance at a spacing of 0.25-0.30 eV, consistent with single electron charging. However, under light irradiation, we observe a second regular resonance, for negative tip biasing less than -1 eV, that modulates the charging structure at ∼ 1.0 eV period, consistent with the particle's quantum energy level spacing. This paves the way for operation of high-temperature Si-based single electron devices.