The purpose of this research is to develop an optimal method for synthesizing of nanocrystalline Al2O3 monolayers at high growth rates on cemented carbides coated with an intermediate layer of pre-Al2O3-C (composite layers Al2O3-C/Al2O3). The use of quartz glass substrate allows for obtaining information about the quality of the layers such the thickness and density, because of its high transparency. The Al2O3 layers that do not containing carbon were synthesized on quartz glass by MOCVD using aluminum acetylacetonate and air as the reactants at temperatures of 700-1000°C. Argon was also a carrier gas. The resulting layers were transparent, as homogeneous nucleation did not occur during the synthesis process. The layers synthesized at lower temperatures were subjected to a crystallization process at temperatures above 900°C. The crystallization process was studied as a function of time and temperature. The obtained layers were characterized by their nanocrystalline microstructure.