Resonant tunnelling through individual Au nanoclusters embedded in ultrathin SiO2 films studied by Tunnelling AFM

The observation of the resonant electron tunnelling through the individual Au nano-clusters (NCs) embedded in the ultrathin (4-5 nm thick) SiO2 films on n-Si(001) substrates by Tunnelling Atomic Force Microscopy (TUNA) at 300K is reported. The nanocomposite SiO2:NC-Au structures with Au NCs 3-7 nm in lateral size and 1-2 nm in thickness were formed by Pulsed Laser Deposition (PLD). The spots of increased probe current (or the current channels) on the sample surface 3-10 nm in diameter attributed to the electron tunnelling through the individual Au NCs have been observed. The I-V curves of the probe-to-sample contact measured in the current channels having larger (5-10 nm) size exhibited Coulomb staircase while those measured in the smaller channels exhibited the peaks attributed to the resonant tunnelling through the Au NCs less than 1 nm in thickness. In order to explain the experimental results we had employed a double barrier Pt/SiO2/Au/SiO2/Si structure model, which has provided a satisfactory description of the obtained experimental data.