Nanoengineering of Ferroelectric Perovskites by Low Temperature Atomic Layer Deposition

Mariona Coll^a

^aInstitut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain, Campus UAB, Bellaterra, Spain

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe September Meeting 2015 (NFM15)

Santiago de Compostela, Spain, 2015 September 6th - 15th

Invited Speaker, Mariona Coll, presentation 104
Publication date: 8th June 2015

Preparation of perovskite oxide thin films at very low temperatures, over large areas and compatible with low-cost and flexible substrates offers great industrial potential. The degree of crystal perfection required for these perovskites varies according to specific application. However, in general, high temperature thermal treatments and textured growth are required for improved functional properties. This adds complexity in the materials processing in device integration. The unique characteristics of conformality, atomic scale control and low temperature deposition that atomic layer deposition (ALD) technique offers can have direct technological applications: well controlled interfaces, smaller and more demanding structures (3D substrates), increased density of devices and integration in multilayer systems. However, ALD of ternary oxides such as perovskite oxides is still in its early stages. Among the perovskite oxides, BiFeO3 (BFO) holds great potential as stable, lead-free material that simultaneously presents ferroelectric and magnetic order at room temperature. Interestingly, A- and B- site engineering (ABO3) can strongly modify their properties such as leakage current, ferroelectric properties and even the band gap. From a theoretical point of view, Bi-based perovskites (i.e. BiCoO3) are very interesting materials as they offer large variations in crystal symmetries, polarity, magnetic and ferroelectric properties (Ps=175 μC/cm2 and band gap of 0.9 eV), however, most of them can only be prepared at high-pressure high-temperature conditions and with low Co content. Here we study for the first time the low temperature stabilization (<300ºC) of Bi1-x(Fe,Co)xO3 (BFCO) thin film solid solutions by ALD. By x-ray photoelectron spectroscopy and piezoelectric force microscopy we demonstrate that ALD allows stabilization and compositional tuning of ferroelectric BFCO solid solution with high concentrations of Co. Structural properties have been evaluated by x-ray diffraction and scanning transmission electron microscopy. We will also show the feasibility to conformaly coat 3D substrates with BFO.

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