| Thin film deposition by chemical vapor deposition (CVD) techniques plays a dominant role in the development of both protective and functional coatings, important for their technological implications. Commonly, multi-component materials are prepared from a mixture of precursors, however the efficiency of such processes is hampered by the mis-match of chemical reactivity such as differential thermal stability and vapor pressure of individual precursor species. Consequently, phase separation and elemental segregation are usually observed in coatings produced by CVD. De-mixing of elements in multi-component systems is thermodynamically driven and sensitive to the chemical behavior of the precursors. Transformation of precursor compounds possessing bonding features inherent to the solid-state lowers the need of diffusion and counterbalances the thermodynamic impediments. We discuss here the role of pre-defined chemical precursors in reducing the constraints imposed on conventional CVD techniques, which require rather high deposition temperatures and generally offer marginal control over microstructure and surface topography. Examples dealing with the decomposition of molecular sources in CVD process to deposit gas sensing, photocatalytic and bio-compatible coatings are also presented. |
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