ABO₃-type Ferroelectric Films Grown By L-MBE System

ABO3-type ferroelectric films caught great attention, since their interesting physical properties and simple structures. Among them, BiFeO3became hot research issue for its ferroelectricity and anti-ferromagnetism at room temperature. Further more, BiFeO3is lead free material with large remnant polarization. These properties make BiFeO3promising material for memories and sensors. Recent years, although some papers have reported photovoltaic effect of BiFeO3, few report has focused on optical properties of BiFeO3. BaTiO3is a kind of classic ferroelectronics. Because of the high dielectric constant, piezoelectric, ferroelectric, and a series of optical properties, BaTiO3has applications in electronic and optical devices.However, high quality films are required for both fundamental study and applications. In this paper L-MBE system was employed to deposit BiFeO3and BaTiO3films. Structures, optical and electrical properties were also tested. Details are as follows:Optimize the process of solid-state method to fabricate R3c BiFeO3ceramics. Pure phase BiFeO3ceramics were fabricated by liquid-state method.SrTiO3single crystal films were grown on SrTiO3substrates, then SrRuO3single crystal films were deposited on SrTiO3films, BiFeO3single crystal films were grown on SrRuO3films at last. STEM was employed to study the structure and growth mechanism of BiFeO3. Affected by the compressive stress from the out-of-plane and in-plane lattice constants are α=3.9156A and c=4.0288A, respectively (bulk:a=c=3.97A). The intermittent growing method was employed to deposit BiFeO3ultra-thing films, finding the step-like structure.Deposite (100) oritation BiFe1-xZnxO3films (x=0,3%,5%,7%and10%) on LaNiO3/Si substrates. The increasing Zn dopant makes the blue shift of Raman scattering, and leads to B-M effect, which finally causes the band gap increases from2.74eV to2.80eV.Deposit BaTiO3single crystal films and BaTiO3/SrRuO3/SrTiO3heterostrcture on SrTiO3substrates. The out-of-plane and in-plane lattice constants are a=3.9617A and c=3.9714A, respectively. This can been explained by the compressive stress and misfit. The Pr value of BaTiO3single crystal films deposited by continuously growth method is11.6μC/cm2.