The deposition of metal oxide layers is of increasing interest. Their properties open up a large field of applications. E. g. Al2O3 layers on cutting tools provide hardened surfaces with increased resistance functionality. Furthermore, the density, adhesion and diffusion barrier properties of alumina coatings make them quite valuable for aerospace propulsion applications. The Al2O3 film can be deposited using plasma-enhanced chemical vapour deposition (PECVD) with aluminum tri-isopropoxide (ATI) as precursor gas. That means the properties of the layer are strongly influenced by the ATI-containing plasma. Thus, a better understanding is needed in order to further improve the deposition of alumina. The aim of the work is to obtain general information about the ATI formation and to study its conversion into by-products using FTIR diagnostic. These tasks have been investigated by studying the influence of the variation of several parameters, i.e. gas mixing ratio, pressure and power.