Imaging gold clusters on TiO2(110) at elevated pressures and temperatures

Variable temperature scanning tunneling microscopy (STM) has been used to image oxide-supported nanoclusters of Au at temperatures from 300 to 450 K and oxygen pressures from 10−10 to 4 Torr. Oxygen-induced morphological changes of the TiO2(1 × 2) reconstruction are apparent at room temperature and prolonged exposure (∼3 × 103 L (langmuir)) at 10−4 Torr oxygen. Gold clusters with diameters smaller than ∼4 nm are unstable toward sintering at ca. 450 K and oxygen pressures >10−1 Torr. Oxygen at pressures >10−4 Torr weakens the interaction between the gold cluster and the titania support. Increasing the sample temperature to >300 K facilitates disruption of the cluster–support interaction.