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. Pérez-Mezcua 1,2 , R. Sirera 2 , I. Bretos 1 , J. Ricote 1 , R. Jiménez 1 , L.Fuentes- Cobas 3 , R. Escobar-Galindo 1 , D. Chateigner 4 , L. Lutterotti 4 and M. L. Calzada 1 1.Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) 2.Universidad de Navarra 3.CIMAV- México 3.CIMAV- México 4.CRISMAT-ENSICAEN-France Zaragoza, 20 de junio de 2013 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
1. INTRODUCTION Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
1. INTRODUCTION Actual trends in electronical devices Thin film Lead free composition (1-x)(Bi 0.5 Na 0.5 )TiO 3 -xBaTiO 3 (BNBT) BNBT phase diagram reported in 1991 Pb(Zr,Ti)O Pb(Zr,Ti)O 3 The same as MPB-BNBT MPB Welberry et al, Metalll and Materials Trans , 2010 , A 41, 1110-1118 Takenaka et al, Jpn J Appl Phys , 1991, 30, 2236-39 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
1. INTRODUCTION Morphotropic phase region in (1-x)(Bi 0.5 Na 0.5 )TiO 3 -xBaTiO 3 (BNBT) Bulk ceramics BNBT6.0 BNBT7.0 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 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
1. INTRODUCTION (1-x)(Bi 0.5 Na 0.5 )TiO 3 -xBaTiO 3 (BNBT) thin thin films films Easy volatilization of high vapour pressure elements Excesses of these elemens: Bi 3+ and Na + Drawbacks of the excesses incorporation Film Film/substrate Reaction interface interface Substrate Cross contamination Cross contamination Stresses development during the thermal treatments A shift of the MPB in thin Change of the cell film with respect to the parameters bulk ceramic C. Dragoi et al, Appl Surf Sci, 2011 , 257, 9600-05 I. Bretos et al, Mater Lett, 2011 , 65, 2714-16 Instituto de Ciencia Instituto de Ciencia N. Scarisoreanu et al , Appl Surf Sci, 2007, 2544, 1292-1297 de Materiales de Madrid de Materiales de Madrid H. W. Cheng et al , Appl Phys Lett, 2004 , 85, 2319-21
2. EXPERIMENTAL PROCEDURE Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
2. EXPERIMENTAL PROCEDURE BNBTxs BNBT Alonso-Sanjosé et al, J Am Ceram Soci, 2008, 92 [10], 2218-25 BNBT thin film • Spin coating Fabrication of • Rapid Thermal BNBT films: CSD Instituto de Ciencia Instituto de Ciencia Processing de Materiales de Madrid de Materiales de Madrid
2. EXPERIMENTAL PROCEDURE Structural study: X-ray diffraction Four-circle XRD diffractometer Grazing Incidence X-ray diffraction using Synchrotron radiation Store ring Stanford Synchrotron Radiation Laboratory 2 θ χ ω φ Beam line Synchrotron light Synchrotron light λ λ =0.97354 Ǻ λ λ Compositional study: Rutherford backscattering CRISMAT-ENISCAEN spectroscopy (RBS) France Instituto de Ciencia Instituto de Ciencia W. K. Chu et al, “Backscattering Spectrometry”,1978 Academic Press, de Materiales de Madrid de Materiales de Madrid New York
3. RESULTS AND DISCUSSION Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
3. RESULTS BNBT5.5 thin film (Stoichiometric) Structural study Rietveld refinement BNBT3.5 BNBT5.5 BNBT10.0 Crystal system Rhombohedral Rhombohedral Tetragonal Tetragonal Space group R3m R3m P4mm P4mm a R (Å) / a T (Å) 3.817 3.857 3.871 3.868 α R ( o ) / c T (Å) 89.861 89.460 3.890 3.891 Volume fraction (%) 99.9 71.0 28.9 95.3 χ 2 1.083 1.153 1.165 Maud - Materials Analysis Using Diffraction Instituto de Ciencia Instituto de Ciencia http://www.ing.unitn.it/~maud/ de Materiales de Madrid de Materiales de Madrid
3. RESULTS BNBT10.0xs thin film (Excesses) Structural study Rietveld refinement BNBT5.5xs BNBT10.0xs BNBT15.0xs Crystal system Rhombohedral Rhombohedral Tetragonal Tetragonal Space group R3m R3m P4mm P4mm a R (Å) / a T (Å) 3.863 3.868 3.873 3.869 α R ( o ) / c T (Å) 89.499 89.616 3.895 3.889 Volume fraction (%) 96.4 82.4 17.(5) 95.7 χ 2 1.177 1.162 1.149 Instituto de Ciencia Instituto de Ciencia Maud - Materials Analysis Using Diffraction de Materiales de Madrid de Materiales de Madrid http://www.ing.unitn.it/~maud/
3. RESULTS Grazing incidence X-ray synchotron Radiation:BNBT10.0xs Structural study Low incident angle (~70nm) 2D patterns P4mm Secondary phase High incident angle High incident angle (~200nm) (~200nm) 2D patterns R3m - + Rhombohedral Rhombohedral Tetragonal Tetragonal P4mm+R3m volume fraction volume fraction volume fraction volume fraction + - Substrate http://www.esrf.eu/computing/scientific/ANAELU/Anelu_Page.htm L. Fuentes-Montero et al, In: SSRL/LCLS User's conference , 2009 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
3. RESULTS Compositional study Rutherford Backscattering (RBS) experiments BNBT5.5 thin film BNBT10.0xs thin film 25000 30000 BNBT5.5 Experimental Pt 25000 Fitted 20000 Ba Bi unts (a.u.) 20000 nts (a.u.) 15000 15000 Coun Count 10000 10000 10000 BNBT10.0xs 5000 5000 Bi O Ti Na Ba 0 0 500 600 700 600 800 1000 1200 1400 1600 1800 2000 Energy (KeV) Energy (KeV) Larger thickness and Experimental and fitted spectra thicker interface for the of the BNBT5.5 thin film BNBT10.0xs thin film .Kotai, Nucl Instrum Methods, 1994, B 85 , 588–96, M. Mayer, “SIMNRA User's Guide”, 1997 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
3. RESULTS Compositional Compositional depth profile study 100 100 Pt BNBT5.5 thin film BNBT10.0xs thin film 80 80 Composition (%) Composition (%) Pt O O 60 60 40 40 Bi Bi Ti Ti 20 20 20 Bi Bi Bi O Na Ba Na Ba 0 0 18 18 18 18 18 18 18 18 18 18 0 0 1x10 2x10 3x10 4x10 5x10 1x10 2x10 3x10 4x10 5x10 2 ) 2 ) Depth (atom/cm Depth (atom/cm - Bismuth BNBT10.0 ~375nm BNBT5.5 ~325nm Abrupt content + Bi x Pt interface Pt/TiO 2 /SiO 2 /(100)Si Pt/TiO 2 /SiO 2 /(100)Si .Kotai, Nucl Instrum Methods, 1994, B 85 , 588–96, M. Mayer, “SIMNRA User's Guide”, 1997 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
3. RESULTS FEG-SEM BNBT5.5 thin film micrographs 1 � m 2 � m BNBT10.0xs thin film 1 � m 2 � m Thickness by SEM by RBS Taking into account, the ∼ ∼ 340 nm ∼ ∼ ∼ 325 nm ∼ ∼ ∼ BNBT5.5 theoretical density of the BNBT (5.96 g cm -3 ) BNBT10.0xs ∼ ∼ ∼ 550 nm ∼ ∼ ∼ 375 nm ∼ ∼ Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
4. CONCLUSIONS Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
4. CONCLUSIONS Excesses 100 BNBT films BNBTxs films 90 Stoichiometric Rhombohedral volume phase (%) Compositional shift of the MPB 80 Bi 3+ and Na + excesses 70 60 50 Secondary phase at the surface 40 Accordance with data 30 (BNT /BT) MPB MPB reported for bulk ceramics 20 Bi x Pt 10 MPB MPB Substrate 0 6 8 10 12 14 BaTiO 3 (mol %) Dense stoichiometric BNBT perovskite Substrate 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 Bi 3+ and Na + excesses remain in the bulk film, as second phases or incorporating to the A-sites of the perovskite. • Bi 3+ 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. Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
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 Instituto de Ciencia Instituto de Ciencia de Materiales de Madrid de Materiales de Madrid
Recommend
More recommend
