Influence of two-dimensional oxide nanosheets seed layers on the growth of (100)BiFeO3 thin films synthesized by chemical solution deposition

Abstract

Complex oxide thin films of high quality, such as the multiferroic BiFeO3 (BFO) material, are required for integrated oxides electronics. However, the properties of these materials are strongly dependent on their crystalline orientation and their optimal performances are usually obtained on expensive single-crystal substrates. A lower cost alternative approach is the use of oxide nanosheets seed layers that can be deposited on any substrate, including silicon (Si) used in CMOS technology, for the growth of complex oxides with the desired crystallographic orientation. In this work, BFO films were deposited by chemical solution deposition using polymeric precursor method. First, the optimization of synthesis parameters was performed on amorphous silica and on (100)Si substrates. The structural and microstructural characterizations revealed a polycrystalline growth of the BFO films on both substrates and showed the influence of the synthesis temperature, in particular to obtain the pure perovskite phase. The influence of a two-dimensional nanosheets seed layer was then investigated. Ca2Nb3O10− nanosheets were prepared by the exfoliation process of HCa2Nb3O10 phase that is obtained by cation exchange of the layered KCa2Nb3O10 niobate in an acidic solution. The nanosheets were deposited directly on both substrates by Langmuir–Blodgett process, followed by the subsequent deposition of BFO by chemical solution deposition. X-ray diffraction and transmission electronic microscopy experiments showed a highly oriented (100) growth of the BFO thin films confirming the great interest of two-dimensional nanosheets seed layers.