Investigation of Embedded Perovskite Nanoparticles for Enhanced Capacitor Permittivities

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• 作者：Andreas Krause ; Walter M. Weber ; Darius Pohl ; Bernd Rellinghaus ; Marcel Verheijen ; Thomas Mikolajick
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：November 26, 2014
• 年：2014
• 卷：6
• 期：22
• 页码：19737-19743
• 全文大小：355K
• ISSN：1944-8252

文摘

Growth experiments show significant differences in the crystallization of ultrathin CaTiO₃ layers on polycrystalline Pt surfaces. While the deposition of ultrathin layers below crystallization temperature inhibits the full layer crystallization, local epitaxial growth of CaTiO₃ crystals on top of specific oriented Pt crystals occurs. The result is a formation of crystals embedded in an amorphous matrix. An epitaxial alignment of the cubic CaTiO₃ 鉄?11鉄?direction on top of the underlying Pt {111} surface has been observed. A reduced forming energy is attributed to an interplay of surface energies at the {111} interface of both materials and CaTiO₃ nanocrystallites facets. The preferential texturing of CaTiO₃ layers on top of Pt has been used in the preparation of ultrathin metal鈥搃nsulator鈥搈etal capacitors with 5鈥?0 nm oxide thickness. The effective CaTiO₃ permittivity in the capacitor stack increases to 55 compared to capacitors with amorphous layers and a permittivity of 28. The isolated CaTiO₃ crystals exhibit a passivation of the CaTiO₃ grain surfaces by the surrounding amorphous matrix, which keeps the capacitor leakage current at ideally low values comparable for those of amorphous thin film capacitors.

Keywords:

perovskites; nanocrystallites; dielectrics; local epitaxy; surface energy