Journal article

Precursor adsorption efficiency of titanium tetra isopropoxide in the presence of a barium beta-diketonate precursor

Barium titanate is a promising candidate for integrated photonic application due to its high electro-optic coefficient; therefore the need arises for a suitable deposition technique which provides high film quality at low temperatures (below 500 degrees C) and reasonable growth rates. We report on combinatorial high vacuum chemical vapor depositions of titanium(IV) tetra isopropoxide and barium hexafluoroacetylacetonate (hfa)-tetraglyme on silicon substrates aiming at the deposition of barium titanate. The barium precursor was synthesized and characterized regarding its evaporation kinetics. Co-depositions of both precursors were carried out in the absence and presence of reactive gas partners such as H-2, H2O, O-2 and O-3. Plain substrates deposited in the absence of ozone, however, do not show any titanium incorporation. We call this phenomenon obviating precursor interaction. Elongated masking structures were designed and manufactured on silicon substrates to modify locally the precursor impinging rate of one of both precursors to study the nature of this obviating behavior. It was found, that the blocking results from a reduced sticking coefficient, i.e. a fast desorption of the precursor prior to decomposition. When adding ozone, distinct, sharply separated regions were identified on the substrate, which we separate, according to their chemical composition and morphology, into TiO2, Ba-containing and barium and titanium mixed deposit. We found that the transition between TiO2 and Ba-deposit is dependent on the titanium to barium precursor impinging ratio. Depending on the barium precursor flux, the third region of mixed deposition of barium and titanium forms in the Ba deposit. The mixed deposit indicates a promising starting point for a combinatorial high vacuum chemical vapor deposition optimization to evaluate the feasibility of a high quality barium titanate film by this technique. (C) 2013 Elsevier B.V. All rights reserved.


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