Solid-State Diffusive Amorphization in TiO2/ZrO2 Bilayers |
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Authors: | Hyunjung Shin Monika Agarwal Mark R De Guire Arthur H Heuer |
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Affiliation: | Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106 |
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Abstract: | Thin films of crystalline TiO2 were deposited on self-assembled organic monolayers from aqueous TiCl4 solutions at 80°C; partially crystalline ZrO2 films were deposited on top of the TiO2 layers from Zr(SO4)2 solutions at 70°C. In the absence of a ZrO2 film, the TiO2 films had the anatase structure and underwent grain coarsening on annealing at temperatures up to 800°C; in the absence of a TiO2 film, the ZrO2 films crystallized to the tetragonal polymorph at 500°C. However, the TiO2 and ZrO2 bilayers underwent solid-state diffusive amorphization at 500°C, and ZrTiO4 crystallization could be observed only at temperatures of 550°C or higher. This result implies that metastable amorphous ZrTiO4 is energetically favorable compared to two-phase mixtures of crystalline TiO2 and ZrO2, but that crystallization of ZrTiO4 involves a high activation barrier. |
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