Growth of nanoscale BaTiO_3/SrTiO_3 superlattices by molecular-beam epitaxy

Abstract : Commensurate BaTiO3/SrTiO3 superlattices were grown by reactive molecular-beam epitaxy on four different substrates: TiO2-terminated (001) SrTiO3, (101) DyScO3, (101) GdScO3, and (101) SmScO3. With the aid of reflection high-energy electron diffraction (RHEED), precise single-monolayer doses of BaO, SrO, and TiO2 were deposited sequentially to create commensurate BaTiO3/SrTiO3 superlattices with a variety of periodicities. X-ray diffraction (XRD) measurements exhibit clear superlattice peaks at the expected positions. The rocking curve full width half-maximum of the superlattices was as narrow as 7 arc s (0.002 deg). High-resolution transmission electron microscopy reveals nearly atomically abrupt interfaces. Temperature-dependent ultraviolet Raman and XRD were used to reveal the paraelectric-to-ferroelectric transition temperature (TC). Our results demonstrate the importance of finite size and strain effects on the TC of BaTiO3/SrTiO3 superlattices. In addition to probing finite size and strain effects, these heterostructures may be relevant for novel phonon devices, including mirrors, filters, and cavities for coherent phonon generation and control.

[1]  P. Bodin,et al.  Molecular Beam Epitaxy Fabrication of SrTiO3 and Bi2Sr2CaCu2O8 Heterostructures Using a Novel Reflection High-Energy Electron Diffraction Monitoring Technique , 1992 .

[2]  K. Hellwege,et al.  Landolt-Börnstein, Numerical Data and Functional Relationships in Science and Technology , 1967 .

[3]  M. R. Castell,et al.  Scanning tunneling microscopy of reconstructions on the SrTiO3(001) surface , 2002 .

[4]  Jeffrey B. Neaton,et al.  First-principles study of symmetry lowering and polarization in BaTiO3/SrTiO3 superlattices with in-plane expansion , 2005 .

[5]  T. Jackson,et al.  Dielectric functions and optical bandgaps of high-K dielectrics for metal-oxide-semiconductor field-effect transistors by far ultraviolet spectroscopic ellipsometry , 2002 .

[6]  D. Tenne,et al.  Prediction of ferroelectricity in BaTiO3∕SrTiO3 superlattices with domains , 2007 .

[7]  D. Schlom,et al.  Cheap and stable titanium source for use in oxide molecular beam epitaxy systems , 1996 .

[8]  S. K. Streiffer,et al.  Observation of nanoscale 180° stripe domains in ferroelectric PbTiO3 thin films , 2002 .

[9]  Toshimasa Suzuki,et al.  Fabrication of Barium Titanate/Strontium Titanate Artificial Superlattice by Atomic Layer Epitaxy , 1994 .

[10]  A. Tagantsev,et al.  Room-temperature ferroelectricity in strained SrTiO3 , 2004, Nature.

[11]  X. Pan,et al.  Evolution of dislocation arrays in epitaxial BaTiO3 thin films grown on (100) SrTiO3 , 2004 .

[12]  A. Balbashov,et al.  Floating zone growth of high-quality SrTiO3 single crystals , 2003 .

[13]  Y. Jia,et al.  Relaxor ferroelectricity in strained epitaxial SrTiO3 thin films on DyScO3 substrates , 2006 .

[14]  Chang-Beom Eom,et al.  Strain Tuning of Ferroelectric Thin Films , 2007 .

[15]  Darrell G. Schlom,et al.  A Thermodynamic Approach to Selecting Alternative Gate Dielectrics , 2002 .

[16]  D. Tenne,et al.  Probing Nanoscale Ferroelectricity by Ultraviolet Raman Spectroscopy , 2006, Science.

[17]  Horst Rogalla,et al.  Quasi-ideal strontium titanate crystal surfaces through formation of strontium hydroxide , 1998 .

[18]  M. Cardona.  Optical Properties and Band Structure of SrTiO 3 and BaTiO 3 , 1965 .

[19]  D. Riley,et al.  An experimental investigation of extrapolation methods in the derivation of accurate unit-cell dimensions of crystals , 1945 .

[20]  D. Tenne,et al.  Interfacial coherency and ferroelectricity of BaTiO3∕SrTiO3 superlattice films , 2007 .

[21]  D. Norton,et al.  X-Ray Diffraction Measurement of the Effect of Layer Thickness on the Ferroelectric Transition in Epitaxial KTaO 3 / KNbO 3 Multilayers , 1998 .

[22]  V. Gopalan,et al.  Enhancement of Ferroelectricity in Strained BaTiO3 Thin Films , 2004, Science.

[23]  D. Taylor.  Thermal expansion data. VIII: Complex oxides, ABO3, the perovskites , 1985 .

[24]  J. Horwitz,et al.  X-RAY CHARACTERIZATION OF EXTREMELY HIGH QUALITY (SR,BA)TIO3 FILMS GROWN BY PULSED LASER DEPOSITION , 1995 .

[25]  J. Tauc,et al.  Optical properties and band structure of CdSb , 1965 .

[26]  D. Schlom,et al.  RHEED Intensity Oscillations for the Stoichiometric Growth of SrTiO3 Thin Films by Reactive Molecular Beam Epitaxy , 2000 .

[27]  B. Veličkov,et al.  Crystal chemistry of GdScO3, DyScO3, SmScO3 and NdScO3 , 2007 .

[28]  K. Iijima,et al.  Atomic layer growth of oxide thin films with perovskite‐type structure by reactive evaporation , 1992 .

[29]  Multiferroic domain dynamics in strained strontium titanate. , 2006, Physical review letters.

[30]  J. Bednorz,et al.  Crystal growth of strontium titanate SrTiO3 , 1976 .

[31]  S. Phillpot,et al.  Ferroelectric phase transitions and dynamical behavior in KNbO3/KTaO3 superlattices by molecular-dynamics simulation , 2002 .

[32]  T. Kubo,et al.  Surface structure of SrTiO3(100) , 2003 .

[33]  R. Uecker,et al.  Spiral formation during Czochralski growth of rare-earth scandates , 2006 .

[34]  D. Norton,et al.  Long-range ferroelectric interactions in KTaO3/KNbO3 superlattice structures , 1998 .

[35]  R. Bechmann,et al.  Numerical data and functional relationships in science and technology , 1969 .

[36]  D. Tenne,et al.  Acoustic Bragg mirrors and cavities made using piezoelectric oxides , 2007 .

[37]  Theory of polarization enhancement in epitaxial BaTiO3/SrTiO3 superlattices , 2002, cond-mat/0211421.