Ž . Applied Surface Science 134 1998 78–86 TiO thin films by atomic layer deposition: a case of uneven 2 growth at low temperature V. Sammelselg a , A. Rosental a, ) , A. Tarre a , L. Niinisto b , K. Heiskanen c , ¨ K. Ilmonen c , L.-S. Johansson d , T. Uustare e a Institute of Physics, UniÕersity of Tartu, Riia 142, EE-2400 Tartu, Estonia b Laboratory of Inorganic and Analytical Chemistry, FIN-02015 Espoo, Finland c Laboratory of Mechanical Process Technology and Recycling, FIN-02015 Espoo, Finland d Center for Chemical Analysis, Helsinki UniÕersity of Technology, FIN-02015 Espoo, Finland e Institute of Materials Science, UniÕersity of Tartu, EE-2400 Tartu, Estonia Received 26 January 1998; accepted 14 March 1998 Abstract Atomic layer deposition of TiO thin films from TiCl and H O at 1508C was found to result in nonhomogeneous film 2 4 2 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 TiO followed by their 2 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 film, 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 TiO stoichiometric phase, and that the films contain 0.3 mass% of Cl. q 1998 Elsevier 2 Science B.V. All rights reserved. PACS: 81.05.Je; 68.55.ya; 61.16.yd; 82.80.yd Ž . Ž . Keywords: Atomic layer epitaxy ALE ; Atomic layer deposition ALD ; TiO thin films; Amorphous and crystalline phases; In situ and ex 2 Ž . situ characterization; Atomic force microscopy AFM 1. Introduction Electronic, optical, and gas-sensing components can benefit from the recent developments in growing ) Corresponding author. Tel.: q372-7-383025; fax: q372-7- 383033; e-mail: arno@fi.tartu.ee. TiO thin films. In many cases the use of TiO in 2 2 device fabrication has, however, been hampered by the poorly controllable coexistence of phases of dif- ferent structural type. Growing of single-phase com- pact and amorphous TiO thin films continues to be 2 a major problem. Ž . wx Atomic layer epitaxy ALE 1 , often referred to Ž . as atomic layer deposition ALD exploits successive 0169-4332r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 98 00224-4