A new insight into the growth mode of metals on TiO₂(1 1 0)

The growth of metals on TiO₂(1 1 0) at one monolayer coverage is classified into three-dimensional island, two-dimensional layer, and transition growth zones via two thermodynamic parameters, the heat of formation of metal oxides, -Δ_fH_{oxide of M}'⁰ and the heat of sublimation of metals, -Δ_fH_{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(1 1 0) 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(1 1 0) 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, -Δ_fH_{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(1 1 0) and the factors affecting the growth mode. The approach described in this study can also be applied to other metal/reducible oxide systems.