Metal complexes with N-methyldiethanolamine as new photosensitive precursors for the low-temperature preparation of ferroelectric thin films

Abstract

New photosensitive precursors for the low-temperature preparation of ferroelectric PbTiO₃ thin films are obtained by using a sol–gel synthetic route. The reaction of N-methyldiethanolamine (MDEA) with lead acetate and titanium bis(acetylacetonate) diisopropoxide reagents leads to the formation of metal-MDEA complexes with a significant ultraviolet (UV) absorption due to the chromophore groups arisen from the orbital splitting between the respective metal atom and the organic ligand. Processes of transference of charge between the nitrogen and the metallic centre are responsible for the UV absorption in the resulting sols: ligand to metal charge transfer (LMCT) in the case of the Ti(IV) complex, d⁰ element, and metal to ligand charge transfer (MLCT) in the case of the Pb(II) one, d¹⁰ element. The enhanced photosensitivity of the precursor solutions provided by these complexes is exploited for the fabrication of ferroelectric PbTiO₃ films at temperatures compatible with silicon microelectronics (400 °C).