A comparison of gold and molybdenum nanoparticles on TiO2(1 1 0) 1×2 reconstructed single crystal surfaces

The formation and growth of gold and molybdenum nanoparticles were studied by scanning tunneling microscopy on TiO2(1 1 0) surfaces. One to three nm diameter particles of both gold and molybdenum were formed by physical vapor deposition at room temperature. Gold nanoparticles were not stable to even short annealing at 700 K, resulting in significant growth of the particles and reduction in their number. Molybdenum nanoparticles showed remarkable resistance to sintering during short durations of annealing at 700 K. Longer annealing times resulted in significant growth of the molybdenum particles. At intermediate annealing times, nanoscale, anisotropic molybdenum particles were observed. In these cases, the particles formed along the [0 0 1] direction of the surface and were primarily centered on the Ti rows. The differences are attributed to a stronger particle–surface interaction for molybdenum than for gold, due to partial oxidation of molybdenum at the interface. This interfacial reaction is responsible for the slower growth kinetics and anisotropic morphology of the molybdenum particles.