Scanning tunnelling microscopy study of the growth of small palladium particles on TiO2(110)

We studied the thermal stability of small palladium clusters on a TiO2(110) surface. Upon heating the number of particles decreases and the average si ze of the particles increases. This corresponds to a decrease of palladium surface area of this model catalyst. The decrease in particle density canno t be used to distinguish between different kinds of mass transport over the surface, but on the basis of the resulting size distribution we conclude t hat the coalescence of diffusing particles is the main mechanism. This is s upported by a direct observation of mobile clusters. During growth the pall adium clusters change their shape. (C) 2000 Elsevier Science B.V. All right s reserved.