Epitaxy and controlled oxidation of chromium ultrathin films on ferroelectric BaTiO3 templates

Interfaces play a crucial role in the study of novel phenomena emerging at heterostructures comprising metals and functional oxides. In this work, we consider Cr/BaTiO₃ heterostructures grown on Nb:SrTiO₃ (0 0 1) substrates. Chromium thin films with 2 nm nominal thickness are deposited by molecular beam epitaxy on the BaTiO₃ layer, and subsequently annealed in vacuum at temperatures ranging from 800 K to 970 K, and finally exposed to 10⁻⁷ torr of molecular oxygen for 300 s. Highly ordered films are obtained for each of this condition, ranging from metallic Cr to insulating Cr₂O₃ with tetragonal structure. Quite unexpectedly, an intermediate – fully ordered – case exists, with the co-presence of Cr and Cr₂O₃ compounds, each one with its proper crystal orientation. These results show the opportunity of controlling the metal/oxide state of crystalline Cr films grown onto the ferroelectric template BaTiO₃/Nb:SrTiO₃.

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Marco Asa, Christian Rinaldi, Luca Nessi, Daniel Chrastina, Daniela Petti, Edoardo Albisetti, Riccardo Bertacco, Matteo Cantoni. Epitaxy and controlled oxidation of chromium ultrathin films on ferroelectric BaTiO₃, J. Cryst. Growth, 558, 126012 (2021). DOI: https://doi.org/10.1021/acsami.0c21612

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