Photosensitive coordination metal complexes as novel precursors for the low temperature crystallization of metal oxide films: the case of the photoferroic BiFeO3

Metal oxide thin films usually crystallize at temperatures over 600 ºC. This has historically excluded them from a direct integration into flexible electronic systems, since their processing temperatures are several hundred... [ view full abstract ]

Metal oxide thin films usually crystallize at temperatures over 600 ºC. This has historically excluded them from a direct integration into flexible electronic systems, since their processing temperatures are several hundred degrees above the values that flexible substrates can withstand (≤350 ºC). Therefore, a high interest is devoted nowadays to the development of novel chemical solution deposition methods enabling the low-temperature fabrication of metal oxide thin films [1].

Transition and post-transition metals can react with some organic compounds forming photosensitive coordination complexes, where light absorption may induce electronic transitions which promote the crystallization of the metal oxide film at a low temperature [2]. Bi(III) and Fe(III) are among the metal cations that can react with these compounds, obtaining light-absorbing metal complexes as reaction products.

In this work, thin films of multiferroic and photovoltaic perovskites based in the bismuth ferrite (e.g., BiFeO₃, BiFe_1-xCr_xO₃) are prepared. For this, Bi(III) and Fe(III) complexes were synthesized in solution by the reaction of the corresponding cations with alkanolamine and/or dihydroxy alcohol ligands (N-methyldiethanolamine, CH₃N(CH₂CH₂OH)₂, and/or 1,3-propanediol, HO(CH₂)₃OH, respectively). The molecular structure of these metal complexes and the photosensitivity and thermal decomposition of the corresponding solutions are studied here.

BiFeO₃ and BiFe_1-xCr_xO₃ thin films are deposited from the former solutions and crystallized at low temperatures by UV-assisted rapid thermal processing. The ferroelectric and optical properties of these films are determined to evaluate their potential as photoferroic materials.

1. Bretos et al., Chem. Soc. Rev., 2018, 47, 291.
2. Pérez-Mezcúa et al., J. Mater. Chem. C, 2014, 41, 8750

 Supported by Spanish Project MAT2016-76851-R and Fundación General CSIC (ComFuturo Programme).