Berlin 2012 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 44: Poster IV: Thin film photovoltaics; Organic electronics and photovoltaics (jointly with CPP, HL, O); Organic thin films; Trends in atomic layer deposition (Focused session)

DS 44.56: Poster

Freitag, 30. März 2012, 09:30–12:00, Poster E

Guided mode resonance sensors for monitoring film nucleation in atomic layer deposition — •Adriana Szeghalmi, Haiyue Yang, Ernst Bernhard Kley, and Andreas Tünnermann — Institute of Applied Physics, Friedrich Schiller University, Jena, Germany

Thin films produced by atomic layer deposition (ALD) have interesting electrical, optical, catalytic applications. It is well known that the film growth rate in the ALD process is constant, and the ALD film thickness can be precisely controlled through the number of ALD cycles. However, the effect of the substrate surface on the nucleation of the ALD layers is generally unexplored. The surface chemistry will influence the adsorption of the precursors. Depending on the surface material, the film growth might be constant, substrate-inhibited, or substrate-enhanced. The main challenge in the study of ALD film nucleation is the development of in situ detection methods with atomic sensitivity to trace very small amounts of film growing on the substrate surface. Here, we developed guided mode resonance grating (GMRG) sensors for the in situ detection of sub-nm thin coatings. The nucleation of TiO2 on Al2O3 surface has been monitored. The GMRG sensor indicates the formation of ca. 4 Angstrom titania on the alumina surface after two cycles, and a constant growth rate (ca. 0.4 Angstrom/cycle) afterwards. Hence, the number of reactive sites on the Al2O3 surface (OH groups) is much larger than on TiO2. The coverage of alumina with titania is rapidly completed within the first two cycles. The titania layer is already continuous at a film thickness of 4 Angstrom.