A new insight into the growth mode of metals on TiO2(110)

The growth of metals on TiO2(1 10) at one monolayer coverage is classified into three-dimensional island, twodimensional layer, and transition growth zones via two thermodynamic parameters, the heat of formation of metal oxides, -Delta(f)H(oxide of M)(0), and the heat of sublimation of metals, -Delta(f)H(metal, per mol of metal)(0) (both expressed per mol of metal), which are easily obtainable. These two parameters represent the strength of metal/TiO2(110) interfacial interactions and the strength of metal/metal lateral interactions, respectively. Such classification is based on the thermodynamic criteria that the growth mode of metals on TiO2(110) is determined by metal/TiO2 interfacial free energy and metal surface free energy. Compared with the conventional approach that only uses the heat of formation of metal oxides, -Delta(f)H(oxide of O)(0) (expressed per mol of oxygen), our model provides a clearer and more comprehensive vision of the growth mode of metals on TiO2(110) and the factors affecting the growth mode. The approach described in this study can also be applied to other metal/reducible oxide systems. (C) 2002 Elsevier Science B.V. All rights reserved.