TiO2 thin films by atomic layer deposition:: a case of uneven growth at low temperature

Atomic layer deposition of TiO2 thin films from TiCl4 and H2O at 150 degrees C was found to result in nonhomogeneous film growth as a function of time. The unevenness of the growth was ascertained by in situ optical interference technique. In order to obtain a more detailed understanding of the growth behavior, AFM, SEM, EPMA, RHEED, XRD, and XPS measurements were performed on a series of films of different thickness. The data obtained allow us to relate the peculiarities of the growth to the appearance of anatase inclusions in the amorphous base layer of TiO2 followed by their development into crystalline particles. We managed to delimit the nucleation stage of the growth, the stage of the full coverage of the substrate with the amorphous Nm, the stage of the origination of the anatase inclusions, and the final stage at which the polycrystalline film is deposited. The increase of crystallinity and roughness was correlated with the increase of the film thickness and quantitatively determined. It was found that in our films the composition of both the crystalline and amorphous part corresponds to TiO2 stoichiometric phase, and that the films contain 0.3 mass% of Cl. (C) 1998 Elsevier Science B.V. All rights reserved.