Journal of the European Ceramic Society 27 (2007) 4417–4420 Chemical solution deposition and characterization of BiFeO 3 thin films V. Fruth a,∗ , M. Popa a,b , J.M. Calderon-Moreno b , E.M. Anghel a , D. Berger c , M. Gartner a , M. Anastasescu a , P. Osiceanu a , M. Zaharescu a a Institute of Physical Chemistry, 202 Splaiul Independentei street, Bucharest 060021, Romania b Department of Applied Physics and Center for Research in Nano-Engineering (CRNE), Universitat Politecnica de Catalunya, Av. Canal Olimpic s/n 08860, Castelldefels, Barcelona, Spain c University “Politehnica” Bucharest, 1 Polizu street, Bucharest 011061, Romania Available online 30 March 2007 Abstract One of the most interesting category of multifunctional systems is the magnetoelectrics (ME), i.e., materials having simultaneous magnetic and ferroelectric activity. The present paper describes a simple low-temperature synthesis method of preparing bismuth ferrite thin films by a wet chemical route, using bismuth and iron nitrates and two chelating agents (citric acid and polyvinyl alcohol). The films were layer by layer deposited on substrate (silica glass) using the dip-coating technique. The thickness of the layers were controlled by viscosity of the solutions and withdrawing speed parameters. After specific annealing, in air, the samples were characterized by scanning electron microscopy SEM, spectroelipsometry SE, X-ray photoelectron spectroscopy XPS, Raman spectroscopy. A more thoroughly control of the processing parameters seems to be essential in obtaining BiFeO 3 thin films. Solution chemistry variations (differences in precursor type) can have a significant impact on the film properties. © 2007 Elsevier Ltd. All rights reserved. Keywords: Films; Spectroscopy; Optical properties; BiFeO 3 1. Introduction BiFeO 3 – BFO – is known to be the only material that exhibits multiferroism at room temperature. It is a rhombohe- drally (R3c) distorted ferroelectric perovskite with T c ∼ 827 ◦ C (1100 K) and shows G-type antiferromagnetism up to 370 ◦ C (643 K) ∼ T N . 1–3 However, BFO shows unexpectedly small values of the fer- roelectric polarization P s even in a single crystal. Wang et al. 4,5 have fabricated an epitaxial monoclinic pseudotetragonal BFO film having a P s ∼ 90 C/cm 2 almost one order of magnitude higher than that of the bulk BFO by applying a strong compres- sive stress imposed by the bottom structure, SrRuO 3 /SrTiO 3 . It seems that the method of preparation and deposition of films plays a significant role on their properties. ∗ Corresponding author. E-mail address: vfruth@icf.ro (V. Fruth). One practical way to obtain thin ceramic films is the solu- tion deposition technique. The general principle involved in the solution deposition of films is to prepare a “homogeneous” solu- tion of the necessary cation species that may later be coated to a substrate. The fabrication of thin films by this approach involves four basic steps: (i) synthesis of the precursor solution; (ii) depo- sition by spin-coating or dip-coating, where drying processes usually begin depending on the solvent; (iii) low-temperature heat treatment for drying, pyrolysis of organic species (typically 300–400 ◦ C), and formation of an amorphous film; (iv) higher temperature heat treatment for densification and crystallization of the coating into the desired oxide phase (600–1100 ◦ C). For most solution deposition approaches, the final three steps are similar despite differences in the characteristics of the precur- sor solution, and for electronic devices, spin-coating has been used almost exclusively. Depending on the solution route, dif- ferent deposition and thermal processing conditions may be employed to control film densification and crystallization for the preparation of materials with optimized properties. 6 Film properties that could involve changes in solution chemistry 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.02.175