Nanocomposite thin films for miniaturized multi-layer ceramic capacitors prepared from barium titanate nanoparticle based hybrid solutions

Abstract

In the present work a flexible approach for the wet chemical processing of nanocomposite functional thin films is demonstrated. Barium titanate (BTO) based nanocomposite thin films for future miniaturized multi-layer ceramic capacitors are chosen as model systems to introduce the concept of “hybrid solutions” which consist of stabile mixtures of reverse micelle derived BTO nanoparticle dispersions and conventional molecular precursor solutions of either the same (BTO:BTO) or a specifically different material such as zirconia (BTO:ZrO₂). While in the case of using BTO:BTO hybrid solutions an interesting mode of microstructure control is found, the use of BTO:ZrO₂ hybrid solutions with various BTO : ZrO₂ ratios leads to nanocomposite films. BTO:BTO hybrid solutions yield columnar grown films with excellent permittivities up to 1050 with a significantly reduced number of coating steps at 700 °C. Low values of the temperature coefficient of capacitance are realized in the BTO–ZrO₂ nanocomposite thin films. The observed dielectric behavior of these films is explained based on the formation of a core–shell type microstructure on the nanoscale. A detailed high resolution transmission electron microscopy study combined with Raman spectroscopy and X-ray diffraction gives evidence for the proposed BTO–ZrO₂ nanocomposite character of these thin films.