Preparation of functional oxide thin films at very low temperatures, over large areas and compatible with low- cost and flexible substrates, offers great industrial potential. Atomic layer deposition (ALD) is a very appealing chemical thin-film deposition method that is unique because ensures excellent large-area uniformity, conformity, and enables simple and atomic layer control of film thickness and composition. Also, ALD offers well controlled interfaces, nanoengineering of smaller and more demanding structures (3D substrates), and uses lower deposition temperatures than traditional vacuum deposition techniques which guarantee low thermal budget and the possibility to use organic or biological substrates.
The precursor chemistry is one of the main parameters that determines the processing conditions and ultimately the film properties. In spite of the current variety of commercial precursor for the growth of oxides, there are certain requirements associated with these compounds: stability, volatility, non-toxicity, clean decomposition, handling, compatibility under the same deposition conditions... therefore, there is an increasing need to develop new or improved precursors to further boost the deposition of functional oxides by ALD.
In this work we will present the feasibility of two novel precursors to prepare ALD metal oxides. In one case, we demonstrate the use of a cheap, non-toxic and easily handling cobalt precursor to prepare Co3O4 thin films and conformal coatings on 3D TiO2/C nanofibers at low temperature (200 ̊C) with similar growth rates as commercial precursors (1). On the other hand, we explore the use of a single-source heterobimetallic precursor to prepare ternary oxides. The advantages of having the two elements of the final material in a single precursor are threefold: matched stoichiometry, better homogeneity due to the pre-mixed elements and simplified delivery system. We present for the first time the use of a [Gd-Fe based complex] to stabilize by epitaxial growth magnetic GdFeO3 thin films by ALD.
To conclude, the combination of novel chemical precursors and ALD opens a plethora of new opportunities to prepare and nanoengineer functional coatings at low temperature with enhanced functionalities.
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