The photocatalytically assisted decomposition of liquid precursors of metal oxides incorporating TiO2 particles enables the preparation of functional layers from the ferroelectric Pb(Zr,Ti)O3 and multiferroic BiFeO3 perovskite systems at temperatures not exceeding 350 ºC. This enables direct deposition on flexible plastic, where the multifunctionality provided by these complex‐oxide materials guarantees their potential use in next‐generation flexible electronics.
Novel synthetic methods in solution that reduce the formation temperature of bismuth-based electronic oxides are essential for their successful integration with substrates of low thermal stability within microand flexible-electronic devices. This has become crucial for these oxides, since they appear as promising low-toxic functional materials alternative to other electronic oxides containing heavy metals. However, this is a challenge, since the crystallization of bismuth oxides occurs at high temperatures. To overcome these problems, we synthesize here a UV-absorber charge transfer metal complex in solution between the Bi(III) ion and an alkanolamine, N-methyldiethanolamine (Bi(III)-mdea). We take advantage of the photoreactivity of this complex to prepare bismuth-based oxide thin films at low temperature, which cannot be achieved by traditional thermal processing methods. Room temperature stable oxide thin films of the high-temperature d-Bi 2 O 3 phase are prepared from these solutions by UV-irradiation and annealing at 350 C. The efficiency of this synthetic strategy is additionally proven for the low temperature preparation of thin films of much more complex bismuth based functional oxides: the multiferroic bismuth ferrite, BiFeO 3 , and the relaxor-ferroelectric perovskite of bismuth, sodium and barium titanate, (Bi 0.5 Na 0.5 ) 0.945 Ba 0.055 TiO 3 .
Single‐BiFeO3 perovskite films onto Pt‐coated silicon substrates have been fabricated by chemical solution deposition using a synthesis strategy based on the use of nonhazardous reagents. Different routes were tested to obtain precursors for the deposition of the films, inferring that bismuth (III) nitrate and iron (III) 2,4‐pentanedionate dissolved in acetic acid and 1,3‐propendiol led to the best solution. Ferroelectric, magnetic, and optical functionalities were demonstrated in these films, obtaining a high ferroelectric polarization at room temperature, ~67 μC × cm−2, a dependence of the magnetization with the film thickness, 0.60 and 2.50 emu × g−1 for the ~215 and ~42‐nm‐thick films, and a direct band gap in the visible range, Eg ~2.82 eV. These results support the interest of solution methods for the fabrication of BiFeO3 thin films onto the silicon substrates required in microelectronic devices.
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