Initial growth and morphology of thin Au films on TiO2(110)

We have studied the growth of thin Au films (0.2 to 12 nm) and the surface morphology of individual three-dimensional (3D) Au islands on the TiO2(110) surface by using high resolution scanning electron microscopy (HRSEM). The Au is evaporated under UHV conditions onto clean and stoichiometric TiO2(110) with substrate temperatures ranging from 300 to 775 K. In this temperature range, Au grows initially as 3D islands on TiO2(110). At 300 K, the Au film morphology evolves with increasing average Au thickness h, from hemispherical islands initially (h<1.0 nm), to partially coalesced worm-like island structures (h>1.5 nm), to percolation at h similar to 8 nm, and finally to a continuous and rough film at h similar to 12 nm. For deposition at elevated temperature (greater than or equal to 500 K) and for Au thickness greater than or equal to 5 nm, Au islands exhibit faceted shapes. For deposition of greater than or equal to 5 nm of Au at 300 K followed by annealing at 775 K, Au islands are highly faceted with hexagonal shapes. The growth behavior of 1 nm Au on an oxygen-deficient TiO2 surface at 300 K is also reported. (C) 1999 Elsevier Science B.V. All rights reserved.