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Title: Stress Induced Monoclinic Phase in Epitaxial BaTiO3 on MgO

Abstract

We present a detailed strain analysis of epitaxial ferroelectric films taking into account multiple sources of strain, including the lattice mismatch between the film and the substrate, thermal strains due to differences in the thermal expansion coefficients of the film and the substrate, and relaxation by the formation of interfacial dislocations. The lattice parameters of the film are calculated using a thermodynamic formalism coupled with the strain analysis. The theoretical model shows that epitaxial (001) BaTiO{sub 3} films on (001) MgO are expected to display successive phase transformations with decreasing temperatures that are different than the bulk. This is verified experimentally for 50 nm thick (001) BaTiO{sub 3} films grown on (001) MgO substrates at 720 C using pulsed laser deposition. A synchrotron x-ray diffraction study displays two slope changes in the temperature dependence of the out-of-plane lattice constant. This indicates that two phase transformations exist in the film as a function of temperature with transition temperatures and lattice constants that are consistent with the theoretically predicted phases. Theoretical results show that the first transformation at around 270 C corresponds to a paraelectric-ferroelectric transition. The ferroelectric phase has an orthogonal symmetry (Amm2) with in-plane polarization components. The transformation at aroundmore » -20 C is an Amm2<-->Pm transition between two ferroelectric phases. The ferroelectric Pm phase is monoclinic compared to the rhombohedral R3m phase in bulk.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914236
Report Number(s):
BNL-78804-2007-JA
Journal ID: ISSN 0021-8979; JAPIAU; TRN: US200809%%5
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Appl. Phys.; Journal Volume: 99
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BARIUM OXIDES; TITANIUM OXIDES; SUBSTRATES; MAGNESIUM OXIDES; STRESS ANALYSIS; LATTICE PARAMETERS; PHASE TRANSFORMATIONS; TEMPERATURE DEPENDENCE; THERMAL EXPANSION; EPITAXY; FERROELECTRIC MATERIALS; national synchrotron light source

Citation Formats

Misirlioglu,I., Alpay, S., He, F., and Wells, B. Stress Induced Monoclinic Phase in Epitaxial BaTiO3 on MgO. United States: N. p., 2006. Web. doi:10.1063/1.2198938.
Misirlioglu,I., Alpay, S., He, F., & Wells, B. Stress Induced Monoclinic Phase in Epitaxial BaTiO3 on MgO. United States. doi:10.1063/1.2198938.
Misirlioglu,I., Alpay, S., He, F., and Wells, B. Sun . "Stress Induced Monoclinic Phase in Epitaxial BaTiO3 on MgO". United States. doi:10.1063/1.2198938.
@article{osti_914236,
title = {Stress Induced Monoclinic Phase in Epitaxial BaTiO3 on MgO},
author = {Misirlioglu,I. and Alpay, S. and He, F. and Wells, B.},
abstractNote = {We present a detailed strain analysis of epitaxial ferroelectric films taking into account multiple sources of strain, including the lattice mismatch between the film and the substrate, thermal strains due to differences in the thermal expansion coefficients of the film and the substrate, and relaxation by the formation of interfacial dislocations. The lattice parameters of the film are calculated using a thermodynamic formalism coupled with the strain analysis. The theoretical model shows that epitaxial (001) BaTiO{sub 3} films on (001) MgO are expected to display successive phase transformations with decreasing temperatures that are different than the bulk. This is verified experimentally for 50 nm thick (001) BaTiO{sub 3} films grown on (001) MgO substrates at 720 C using pulsed laser deposition. A synchrotron x-ray diffraction study displays two slope changes in the temperature dependence of the out-of-plane lattice constant. This indicates that two phase transformations exist in the film as a function of temperature with transition temperatures and lattice constants that are consistent with the theoretically predicted phases. Theoretical results show that the first transformation at around 270 C corresponds to a paraelectric-ferroelectric transition. The ferroelectric phase has an orthogonal symmetry (Amm2) with in-plane polarization components. The transformation at around -20 C is an Amm2<-->Pm transition between two ferroelectric phases. The ferroelectric Pm phase is monoclinic compared to the rhombohedral R3m phase in bulk.},
doi = {10.1063/1.2198938},
journal = {J. Appl. Phys.},
number = ,
volume = 99,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Epitaxial BiFeO{sub 3} thin films were deposited on SrRuO{sub 3} buffered SrTiO{sub 3} (001) substrates at different growth rates by varying the radio frequency sputtering power. With increasing growth rate, the crystal structure of BiFeO{sub 3} films develops from monoclinic lattice to a mixture phase of tetragonal lattice T{sub 1} with c/a{approx}1.05 and giant tetragonal lattice T{sub 2} with c/a{approx}1.23, finally to a single tetragonal phase T{sub 2}, as shown by high resolution synchrotron x-ray diffraction reciprocal space mappings. The observed phase transitions, induced by film growth rate, offer an alternative strategy to manipulate crystalline phases in epitaxial ferroelectric thinmore » films.« less
  • We report on growth of VO{sub 2} films with M2 monoclinic phase stable at room temperature under atmospheric pressure. The films were grown on quartz glass and Si substrates by using an inductively coupled plasma-assisted reactive sputtering method. XRD-sin{sup 2}{Psi} measurements revealed that the films with M2 phase are under compressive stress in contrast to tensile stress of films with M1 phase. Scanning electron microscopy observations revealed characteristic crystal grain aspects with formation of periodical twin structure of M2 phase. Structural phase transition from M2 to tetragonal phases, accompanied by a resistance change, was confirmed to occur as the temperaturemore » rises. Growth of VO{sub 2} films composed of M2 phase crystalline is of strong interest for clarifying nature of Mott transition of strongly correlated materials.« less
  • The lattice structure of (110)-oriented BiFeO{sub 3} epitaxial thin layers has been identified by synchrotron x-ray diffraction. By using (221) and (22{bar 1}) peaks in the (HHL) zone, a ground state monoclinic M{sub b} phase has been observed with lattice parameters of ({beta}; a{sub m}/{radical}2 and c{sub m})=(89.35{sup o}; 3.985 and 3.888 {angstrom}). These results demonstrate a change in phase stability from rhombohedral in bulk single crystals, to monoclinic in epitaxial thin films with two domain states whose polarization is slightly tilted away from [110] towards [111].
  • Thin crystalline films of Gd{sub 2}O{sub 3} are grown on an atomically flat Ge(001) surface by molecular beam epitaxy and are characterized in situ by reflection high energy electron diffraction and x-ray photoelectron spectroscopy, and ex situ by x-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy. The first stage of the growth corresponds to a cubic (110) structure, with two equiprobable, 90 deg. rotated, in-plane domains. Increasing the thickness of the films, a phase transition from cubic (110) to monoclinic (100) oriented crystallites is observed which keeps the in-plane domain rotation, as evidenced by XRD and AFM.
  • An experimental arrangement capable of monitoring temperature changes from 0.01 to 0.1K has been successfully tested for registering the temperature evolution occurring during the tetragonal to monoclinic transformation of an alumina/ceria-stabilized tetragonal zirconia polycrystal (Al[sub 2]O[sub 3]/Ce-TZP). The arrangement is based on a very small thermistor. The data obtained have been used for evaluating the thermal diffusivity of the Al[sub 2]O[sub 3]/Ce-TZP composites.