Effect of the crystalline constitution of TiO2 substrates on the growth of ultrathin Mo layer

Metallic molybdenum was deposited by magnetron sputtering on amorphous and (110) rutile TiO2 substrates. An interfacial reaction between the deposited Mo and the TiO2 substrates generating Ti3 +, Ti2 + oxidation states is evidenced by X-ray photoelectron spectroscopy. Our XPS data suggest, as compared to the (110) rutile substrate, a higher reactivity of the amorphous TiO2 leading to a stronger Mo oxidation. In both cases, this reaction, leads to the formation of MoOx nanostructures at the interfaces. The growth mechanism of the Mo deposit as a function of the crystalline constitution of the TiO2 substrate was analyzed by processing the XPS data using the Quases ® software. The data reveal a layer-by-layer growth of the Mo deposit on the (110) rutile substrate and a Stranski–Krastanov growth on the amorphous one. We explain these different growth modes based on the TiO2 surface reactivity and electronic structure using the Cabrera–Mott theory. This explanation is supported by Time-of-Flight Secondary Ion Mass spectrometry profiling.