Structure re(inement of strained LaVO 3 thin (ilm.

Transcription

1 Structure re(inement of strained LaVO 3 thin (ilm. H. Rotella, 1 M. Morales, 2 P.Roussel, 3 H. Ouerdane, 1 D. Chateigner, 1 P. Boullay, 1 L. Lutterotti, 4 and W. Prellier. 1 1 Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN et Université de Caen, 6 Bd Maréchal Juin, Caen Cedex 4, France 2 Laboratoire CIMAP, CNRS UMR 6252, ENSICAEN et Université de Caen, 6 Bd Maréchal Juin, Caen Cedex 4, France 3 Laboratoire UCCS, CNRS UMR 8181, ENSCL, Bat C7a BP F Villeneuve d Ascq, France 4 Dipartimento di Ingegneria dei Materiali, Univ. Di Trento, I Trento, Italy 04/10/2014 Hélène Rotella CRISMAT 1

2 Introduction : epitaxial thin (ilm structure determination Ø Very dif(icult to characterize precisely due to : " Reduced amount of material " Substrate signal " Textured material " Residual stress Ø Induced problem " Weak re(lection " Overlapping of the substrate and the (ilm Ø Experimental methodology : " Local measurement using transmission electron microscopy (microstructure resolution) " Average measurement using High Resolution X- Ray Diffraction analysis (structure re(inement) 04/10/2014 Hélène Rotella CRISMAT 2

3 Introduction : perovskites and distortion mechanisms ü Oxide perovskites : Very interesting compounds for physical properties (CMR, superconductivity, insulator- to- metal transition,..): Ø Perovskite type compound ABO 3 " Space group Pm- 3m (aristotype) Ø Distortion " Jahn- Teller effect " Octahedral tilting " Cation displacements A B O Ø Effect on physical properties " Orbital overlapping In bulk compounds : cation size In thin (ilm : epitaxial strain (metastable phases) Structural characterization Figure adapted from Rondinelli et al., MRS bull., 37, 261 (2012). 04/10/2014 Hélène Rotella CRISMAT 3

4 Introduction on LaVO 3 ü Bulk LaVO 3 crystallographic room T (Mott insulator,afm T N = 143K ): 1 Ø Orthorhombic (Pnma) Ø Lattice parameters : a=5.5529(2) Å, b=7.8447(3) Å and c=5.5529(3)å (a p ~3.92 Å) Ø Atomic positions : Ø Phase transition at about 140K toward a monoclinic structure 1 Bordet et al., JSSC, 106, 253 (1993). La V1 V2 O1 O2 O3 X Y z (4) (8) (6) (10) (6) (4) (6) /10/2014 Hélène Rotella CRISMAT 4

5 Introduction on LaVO 3 ü LaVO3 thin (ilm grown on SrTiO3 (001) oriented substrate by pulsed laser deposition. Ø Ø Under biaxial stress (- 3.6(1) GPa along (10-1)), we have to consider a lower symmetry! Monoclinic Rotella et al, PRB,85, (2012). La V1 V2 O1 O2 O3 X Y z (4) (8) (6) (10) (6) (4) (6) x y z 04/10/2014 Hélène Rotella CRISMAT 5

6 Introduction on LaVO 3 ü LaVO3 thin (ilm grown on SrTiO3 (001) oriented substrate by pulsed laser deposition. Ø Ø Under stress, we have to consider a lower symmetry! 10 atomic positions to revine Rotella et al, PRB,85, (2012). La V1 V2 O1 O2 O3 X Y z (4) (8) (6) (10) (6) (4) (6) x y z 04/10/2014 Hélène Rotella CRISMAT 6

7 ü Electron microscopy measurement Ø Cross- section observation : Experimental measurement Main re(lection : perovskite subcell Extra re(lections coming from octahedral tilting Presence of oriented domains Bulk like structure (Pnma or lower symmetry) Contribution of the domains in the X- ray analysis. 04/10/2014 Hélène Rotella CRISMAT 7

8 Experimental set- up ü High resolution X- ray diffraction (HRXRD) method (P. ROUSSEL, UCCS, Lille): Ø High resolution con(iguration of a Rigaku diffractometer: Rotative anode 4- circles con(iguration : 04/10/2014 Hélène Rotella CRISMAT 8

9 Experimental set- up ü High resolution X- ray diffraction (HRXRD) method (P. ROUSSEL, UCCS, Lille): Ø High resolution con(iguration of a Rigaku diffractometer: Symmetric and coplanar con(iguration : Beam imprint 04/10/2014 Hélène Rotella CRISMAT 9

10 Experimental set- up ü High resolution X- ray diffraction (HRXRD) method (P. ROUSSEL, UCCS, Lille): Ø High resolution con(iguration of a Rigaku diffractometer: Non- symmetric and coplanar con(iguration : Beam imprint 04/10/2014 Hélène Rotella CRISMAT 10

11 Experimental set- up ü High resolution X- ray diffraction (HRXRD) method (P. ROUSSEL, UCCS, Lille): Ø High resolution con(iguration of a Rigaku diffractometer: Non- symmetric and non- coplanar con(iguration : Beam imprint 04/10/2014 Hélène Rotella CRISMAT 11

12 Experimental measurement ü High resolution X- Ray diffraction measurement (HRXRD): Ø Reciprocal space map in coplanar con(iguration (003)STO /(303)LVO Resolution sphere (421)LVO 04/10/2014 Hélène Rotella CRISMAT 12

13 Experimental measurement ü High resolution X- Ray diffraction measurement (HRXRD): Ø Reciprocal space map in coplanar con(iguration Resolution sphere film substrate Ø 11 revlections 04/10/2014 Hélène Rotella CRISMAT 13

14 Experimental measurement ü High resolution X- Ray diffraction measurement (HRXRD): Ø Reciprocal space map in non- coplanar con(iguration (033)LVO Resolution sphere Ø 11 additional revlections are observed Ø A total of 22 revlections 04/10/2014 Hélène Rotella CRISMAT 14

15 Reciprocal space map analysis ü High resolution X- Ray diffraction measurement: " Integrated intensity of the reciprocal lattice point related to atomic positions " Ellipse centre position related to cell parameters " Gap between centres due to misalignment and stress. " Reciprocal lattice point shape depending on (ilm texture : " tilt, twist, coherence length ( lateral and vertical) 04/10/2014 Hélène Rotella CRISMAT 15

16 Reciprocal space map analysis ü Intensity integration (software development made by H. OUERDANE): Numerical Vit: v Noise level v Background v Integrated intensity Integrated intensity of the 22 RSM Implementation in revinement structure software : Atomic positions revinement 04/10/2014 Hélène Rotella CRISMAT 16

17 Conclusion ü Conclusion: Ø This work is the study of a LaVO 3 thin (ilm structure using High resolution X- ray diffraction " The experimental methodology is well established " RSM Integrated intensities exported. " Atomic positions re(inement is under way! ü Future work (ongoing): Ø Re(inement of all the parameters of the thin (ilm structure using MAUD Program, 04/10/2014 Hélène Rotella CRISMAT 17

18 04/10/2014 Hélène Rotella CRISMAT 18

19 Outline Ø The objective of this study is to characterize the structure of a LaVO 3 (LVO) strained thin Vilm grown on SrTiO 3 (001)- oriented substrate. " Introduction : thin (ilm structure determination " Experimental set- up " Experimental measurement on LaVO 3 thin (ilm. " Methodology on the structure re(inement. 04/10/2014 Hélène Rotella CRISMAT 19

20 Residual stress Ø Generalized Hooke s law: Ø Stiffness tensor from Khan et al.: 1 Ø Rotational matrix from crystalline orientation: 04/10/2014 Hélène Rotella CRISMAT 20

21 Intensity correction µ : linear absorption coef(icient T : thickness