On the Reliability of Heteronuclear Precursors-Ligand Effects in the Li-MOCVD Synthesis of SrTiO3 Films
Autor: | M. Andrieux, Suresh Gohil, Vadim G. Kessler, Magali Brunet, Gulaim A. Seisenbaeva, C. Legros, Patrick Ribot |
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Rok vydání: | 2011 |
Předmět: |
Materials science
010405 organic chemistry Ligand Biomedical Engineering Oxide Bioengineering General Chemistry 010402 general chemistry Condensed Matter Physics 01 natural sciences 0104 chemical sciences chemistry.chemical_compound chemistry Heteronuclear molecule Alkoxide Strontium titanate Physical chemistry Molecule General Materials Science Thin film Stoichiometry |
Zdroj: | Journal of Nanoscience and Nanotechnology. 11:8302-8308 |
ISSN: | 1533-4899 1533-4880 |
Popis: | Strontium titanate SrTiO3 thin films are highly perspective as gate dielectric material. Difference in volatility of the common homometallic precursors-strontium beta-diketonates and titanium alkoxides remains major hinder for preparation of high quality coatings based on this phase. An attractive alternative in its synthesis by MOCVD is provided by application of heterometallic mixed-ligand complexes, Sr2Ti2(beta-diket)4(OR)8(ROH)x. Mass-spectrometric study reveals, however, that none of these species can be considered a true single-source precursor. The relative stability of the molecules in solution and the congruence of in-situ release of homometallic species on evaporation are, on the other hand, crucial for the quality of the produced films and are strongly influenced by the nature of alkoxide ligands, OR. The historically first discovered representative of this heterometallic family, a sec-alkoxide derivative Sr2Ti2(thd)4(O(i)Pr)8, is in fact unexpectedly unstable, transforming in solution into Sr2Ti(thd)4(O(i)Pr)4((i)PrOH), which explains difficulties in keeping the correct stoichiometry using isopropoxide precursor. The primary alkoxide complexes, Sr2Ti2(thd)4(OR)8(ROH)2, R = Et, (n)Pr are also unstable yielding Sr4Ti2(thd)4(OR)8(ROH)2 on decomposition. The best solution stability and most uniform evaporation was observed for the iso-derivative, Sr2Ti2(thd)4(O(i)Bu)8, permitting to apply it in long term experiments under industrial process conditions. Present contribution provides detailed experimental comparison between and sec-and iso-alkoxide derivatives and sheds light on the influence of the ligand on molecular stability of a precursor and how it influences the quality of the derived oxide film, especially in relation to its electrophysical properties. |
Databáze: | OpenAIRE |
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