CRYSTALLINE STRUCTURES AND COMPOSITIONAL DEPTH PROFILE OF LEAD-FREE - - PowerPoint PPT Presentation

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CRYSTALLINE STRUCTURES AND COMPOSITIONAL DEPTH PROFILE OF LEAD-FREE (Bi 0.5 Na 0.5 ) 1-x Ba x TiO 3 THIN FILMS AROUND THE MORPHOTROPIC PHASE BOUNDARY. D. Prez-Mezcua 1,2 , R. Sirera 2 , I. Bretos 1 , J. Ricote 1 , R. Jimnez 1 , L.Fuentes-

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SLIDE 1

CRYSTALLINE STRUCTURES AND COMPOSITIONAL DEPTH PROFILE OF LEAD-FREE (Bi0.5Na0.5)1-xBaxTiO3 THIN FILMS AROUND THE MORPHOTROPIC PHASE BOUNDARY.

  • D. Pérez-Mezcua1,2, R. Sirera2, I. Bretos1, J. Ricote1, R. Jiménez1, L.Fuentes-

Cobas3, R. Escobar-Galindo1, D. Chateigner4, L. Lutterotti4 and M. L. Calzada1

1.Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) 2.Universidad de Navarra 3.CIMAV- México

Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid

3.CIMAV- México 4.CRISMAT-ENSICAEN-France

Zaragoza, 20 de junio de 2013

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SLIDE 2

Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid

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SLIDE 3
  • 1. INTRODUCTION

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SLIDE 4
  • 1. INTRODUCTION

Actual trends in electronical devices

Lead free composition Thin film

(1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (BNBT)

Pb(Zr,Ti)O

BNBT phase diagram reported in 1991

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Welberry et al, Metalll and Materials Trans ,2010, A 41, 1110-1118 Takenaka et al, Jpn J Appl Phys ,1991, 30, 2236-39

The same as MPB-BNBT

Pb(Zr,Ti)O3

MPB

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SLIDE 5
  • 1. INTRODUCTION

Morphotropic phase region in (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (BNBT)

BNBT6.0 BNBT7.0 Bulk ceramics

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Pitch et al, J. Eur. Ceram. Soc., 2010, 30, 3445-3453

  • W. Jo et al, J. Appl. Phys. 2011, 109, 014110
  • W. Jo et al, Appl Phys Lett, 2013, 102, 192903
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SLIDE 6
  • 1. INTRODUCTION

Film Substrate

(1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (BNBT) thin thin films films

Easy volatilization of high vapour pressure elements Reaction interface Cross contamination Excesses of these elemens: Bi3+ and Na+

Drawbacks of the excesses incorporation

Film/substrate interface

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Cross contamination A shift of the MPB in thin film with respect to the bulk ceramic

  • C. Dragoi et al, Appl Surf Sci, 2011, 257, 9600-05
  • I. Bretos et al, Mater Lett, 2011, 65, 2714-16
  • N. Scarisoreanu et al, Appl Surf Sci, 2007, 2544, 1292-1297
  • H. W. Cheng et al, Appl Phys Lett, 2004, 85, 2319-21

Stresses development during the thermal treatments Change of the cell parameters

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  • 2. EXPERIMENTAL PROCEDURE

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SLIDE 8
  • 2. EXPERIMENTAL PROCEDURE

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Alonso-Sanjosé et al, J Am Ceram Soci, 2008, 92 [10], 2218-25

BNBTxs BNBT

BNBT thin film

Fabrication of BNBT films: CSD

  • Spin coating
  • Rapid Thermal

Processing

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  • 2. EXPERIMENTAL PROCEDURE

Structural study: X-ray diffraction

Grazing Incidence X-ray diffraction using Synchrotron radiation

Store ring Synchrotron light Beam line

Stanford Synchrotron Radiation Laboratory

Four-circle XRD diffractometer

2θ ω χ φ

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Synchrotron light

Compositional study: Rutherford backscattering spectroscopy (RBS)

  • W. K. Chu et al, “Backscattering Spectrometry”,1978 Academic Press,

New York

λ λ λ λ=0.97354 Ǻ

CRISMAT-ENISCAEN France

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  • 3. RESULTS AND DISCUSSION

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SLIDE 11

BNBT5.5 thin film (Stoichiometric)

Rietveld refinement

  • 3. RESULTS

Structural study

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BNBT3.5 BNBT5.5 BNBT10.0 Crystal system Rhombohedral Rhombohedral Tetragonal Tetragonal Space group R3m R3m P4mm P4mm aR(Å) / aT (Å) 3.817 3.857 3.871 3.868 αR(o) / cT(Å) 89.861 89.460 3.890 3.891 Volume fraction (%) 99.9 71.0 28.9 95.3 χ2 1.083 1.153 1.165

Maud - Materials Analysis Using Diffraction http://www.ing.unitn.it/~maud/

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SLIDE 12

BNBT10.0xs thin film (Excesses)

Rietveld refinement

  • 3. RESULTS

Structural study

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BNBT5.5xs BNBT10.0xs BNBT15.0xs Crystal system Rhombohedral Rhombohedral Tetragonal Tetragonal Space group R3m R3m P4mm P4mm aR(Å) / aT (Å) 3.863 3.868 3.873 3.869 αR(o) / cT(Å) 89.499 89.616 3.895 3.889 Volume fraction (%) 96.4 82.4 17.(5) 95.7 χ2 1.177 1.162 1.149

Maud - Materials Analysis Using Diffraction http://www.ing.unitn.it/~maud/

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SLIDE 13

Low incident angle 2D patterns High incident angle

Grazing incidence X-ray synchotron Radiation:BNBT10.0xs

(~70nm) (~200nm)

Secondary phase

Structural study

  • 3. RESULTS

P4mm

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2D patterns High incident angle

P4mm+R3m

Substrate

Tetragonal Tetragonal volume fraction volume fraction

(~200nm)

http://www.esrf.eu/computing/scientific/ANAELU/Anelu_Page.htm

  • L. Fuentes-Montero et al, In: SSRL/LCLS User's conference, 2009

R3m

Rhombohedral Rhombohedral volume fraction volume fraction

  • +

+

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SLIDE 14

15000 20000 25000 30000

Pt

unts (a.u.)

Experimental Fitted

10000 15000 20000 25000

Ba

nts (a.u.)

Bi BNBT5.5

Rutherford Backscattering (RBS) experiments BNBT5.5 thin film BNBT10.0xs thin film

Compositional study

  • 3. RESULTS

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600 800 1000 1200 1400 1600 1800 2000 5000 10000

Ba Ti

Coun Energy (KeV)

Bi O Na

500 600 700 5000 10000

Count Energy (KeV)

BNBT10.0xs

Larger thickness and thicker interface for the BNBT10.0xs thin film Experimental and fitted spectra

  • f the BNBT5.5 thin film

.Kotai, Nucl Instrum Methods, 1994, B 85, 588–96,

  • M. Mayer, “SIMNRA User's Guide”, 1997
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20 40 60 80 100 O

Composition (%)

Pt Bi Ti 20 40 60 80 100 Bi Pt Ti

Composition (%)

Bi O

Compositional depth profile BNBT5.5 thin film BNBT10.0xs thin film

Compositional study

  • 3. RESULTS

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Bismuth content

1x10

18

2x10

18

3x10

18

4x10

18

5x10

18

Ba Na

Depth (atom/cm

2)

Bi O 1x10

18

2x10

18

3x10

18

4x10

18

5x10

18

20 Na Ba Bi

Depth (atom/cm

2)

BNBT10.0 ~375nm BixPt Pt/TiO2/SiO2/(100)Si

  • +

BNBT5.5 ~325nm Pt/TiO2/SiO2/(100)Si

.Kotai, Nucl Instrum Methods, 1994, B 85, 588–96,

  • M. Mayer, “SIMNRA User's Guide”, 1997

Abrupt interface

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SLIDE 16

BNBT5.5 thin film BNBT10.0xs thin film FEG-SEM micrographs

2m 1m

  • 3. RESULTS

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1m 2m

Thickness by SEM by RBS BNBT5.5 ∼ ∼ ∼ ∼340 nm ∼ ∼ ∼ ∼325 nm BNBT10.0xs ∼ ∼ ∼ ∼550 nm ∼ ∼ ∼ ∼375 nm

Taking into account, the theoretical density of the BNBT (5.96 g cm-3 )

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  • 4. CONCLUSIONS

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6 8 10 12 14 10 20 30 40 50 60 70 80 90 100

Rhombohedral volume phase (%)

BaTiO3(mol %)

BNBT films BNBTxs films

MPB MPB MPB MPB Bi3+ and Na+ excesses

(BNT /BT) BixPt Compositional shift of the MPB Accordance with data reported for bulk ceramics Dense stoichiometric BNBT perovskite

Substrate Substrate

  • 4. CONCLUSIONS

Stoichiometric Excesses Secondary phase at the surface

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Substrate

  • The morphotropic phase boundary (MPB) of the BNBT stoichiometric thin

films is placed at x ~0.055-0.080. This is the MPB region also found for bulk ceramics.

  • For the BNBTxs films, the MPB is located close to x ~0.100. This suggests that

the Bi3+ and Na+ excesses remain in the bulk film, as second phases or incorporating to the A-sites of the perovskite.

  • Bi3+ and Na+ excesses are not required to obtain MPB-BNBT perovskite thin

films with homogenous compositional depth profiles.

  • These structural and compositional characteristics suggest that these films

would have an appropriate functionality for applications in microelectronic devices.

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Acknowledgements This work has been supported by the Spanish Project MAT2010-15365

  • D. Pérez-Mezcua acknowledges the financial support of the FPU Spanish Program
  • Dr. I. Bretos acknowledges the financial support of the Juan de la Cierva Program
  • Dr. R. Escobar-Galindo acknowledges the financial support of the Ramon y Cajal Program

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