Scanning tunneling microscopy/spectroscopy of titanium dioxide nanoparticulate film on Au(1 1 1) surface

Scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS) of titanium dioxide nanoparticulate film on Au(1 1 1) surface is carried out yielding topography, I–V, dI/dV versus V and normalized dI/dV versus V. Isolated nanoparticles were found to exhibit semiconducting behavior with a band gap which varies from 1 to >3.0 eV depending on the nature of substrate/nanoparticle/tip junction formation. Increase in the particulate density resulted into change in tunneling behavior from semiconducting to metallic as characterized by decrease in non-linearity in I–V curves and increase in average tunneling conductance. The results are discussed in terms of presence of adsorbed complexes on defect structure of TiO2 surface for low coverage and availability of additional transport paths between the particles at high coverage.