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

Abstract

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.