C0MBINED TEXTURE-MICROSTRUTURE-PHASES- - - PowerPoint PPT Presentation

“C0MBINED TEXTURE-MICROSTRUTURE-PHASES- STRAINS-STRUCTURE-REFLECTIVITY ANALYSIS”

• D. Chateigner, CRISMAT-ENSICAEN, Caen,

France

• M. Morales, LERMAT-ENSICAEN, Caen, France
• L. Lutterotti, DME, Trento, Italy

• Goals:

– Obtain structure, microstructure, texture and residual stresses of polyphased thin structures by one step methodology – The analysis should not be limited by phase overlapping, strong texture or complex structures

• How/Why ? -> Rietveld + ODF analysis by cyclic full

pattern fitting

– Textured non-destructible materials – Texture / Structure / Strains / Phases … parameters correlation – Final program: MAUD, developed inside the ESQUI European project

• Some examples:

– Ferroelectric thin heterostructures: texture, structure, microstruct. – Nanocrystalline silicon thin films: texture, structure, anisotropic shapes – Amorphous silicon oxynitrides very thin films: Electron Density Profiles – Irradiated fluoroapatites: texture, phase, structure – Bi-based superconductor ceramics: texture, phase, structure, E. Guilmeau, poster VII-P4

Texture from Spectra

From pole figures From spectra Orientation Distribution Function (ODF)

Residual Stresses and Rietveld

Fe

Cu

• Macro elastic strain tensor (I kind)
• Crystal anisotropic strains (II kind)

Macro and micro stresses

C

Applied macro stresses

How it works (RiTA) Texture

• from Generalized Spherical Harmonics:

Ii

calc(χ,φ) =

Sn Lk Fk;n

2S 2θi − 2θk;n

( )P

k;n(χ,φ)A k

∑

n=1 Nphases

∑

+ bkgi

P

k(χ,φ) =

1 2l +1

l= 0 ∞

∑

kl

n χ,φ

( )

n=−l l

∑

Cl

mnkn *m Θkφk

( )

m=−l l

∑

f (g) = Cl

mnTl mn(g) m,n=−l l

∑

l= 0 ∞

∑

• from the WIMV iterative process:

( ) ⎥

⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ =

∏

+ hkl I 1 n hkl n 1 n

) y ( P ) g ( f ) g ( f N ) g ( f

• P

k(χ,φ) =

f (g,ϕ)dϕ

ϕ

∫

Layering

( ) ( ) ( ) ( )

χ ω µ − − χ µ − − =

χ

cos sin / T 2 exp 1 / cos / Tg exp 1 g C

2 1 film top

( ) ( ) ( ) ( )

χ ω µ − χ µ − =

∑ ∑

χ χ

cos sin / T 2 exp / cos / T g exp C C

' i ' i ' i ' i 2 film top layer cov.

Integrated Intensities (Le Bail extraction) Orientation Distribution Function WIMV, E-WIMV Harmonic refinement Rietveld refinement Residual stresses Stress Distribution Function Structural + Microstructural parameters Popa-Balzar analysis, sin2ψ Multiphased, layered samples: Thicknesses Structure, Anisotropic Sizes (Popa rules) µ-strains, Stacking faults (Warren) Phase ratio (amorphous + crystalline) Specular Reflectivity + Electronic Density Profiles Roughnesses, Densities & EDP, Thicknesses Parrat, DWBA, genetic algorithm

Methodology implementation

Experimental needs

ω = 20° ω = 40°

Spectrometer space mapping:

• instrumental resolution correction
• instrumental misalignments

χ 60° 0° χ 60° 0°

Ferroelectric thin heterostructure

• Substrate: 50 nm of Pt electrode + TiO2/SiO2/Si(100)
• 400 nm of Pb0.76Ca0.24TiO3 (PTC) film deposited by spin coating of a sol-gel

solution (CSIC Madrid).

PTC film: harmonic texture model

Triclinic sample symmetry: 1245 parameters only for PTC (Lmax = 22) Reducing sample symmetry to fiber and Lmax to 16: 24 parameters For Pt layer: fiber texture, Lmax = 22 -> 15 parameters Rw = 14.78 %

Observed Fitting

PTC film fitting: WIMV

WIMV 2 layers 2 phases Rw = 25.5% RB = 42.6 % 792 spectra

Observed Fitting

RW = 13%; RB = 12%; Rexp = 22%.(Rietveld) RW = 5%; RB = 6% (E-WIMV)

001, 100 101, 110 111, 111-Pt 002, 200 200-Pt 112, 211 102 201, 210 202, 220 220-Pt

a (Å) thickness (nm) R factors (%)

non-treated substrate

Pt 3.9108(1) 45.7(3) RW=13, RB=12, Rexp=22

annealed substrate

Pt 3.9100(4) 46.4(3) RW=8, RB=14, Rexp=21 Pt (Recryst. 1h) 3.9114(2) 47.8(3) RW=9, RB=20, Rexp=21 Pt (Recryst. 2h) 3.9068(1) 46.9(3) RW=9, RB=14, Rexp=22 Pt (Recryst. 3h) 3.9141(4) 47.5(9) RW=27, RB=12, Rexp=21

Structural parameters

a (Å) c (Å) thickness (nm)

• n non-treated substrate

PCT 3.9156(1) 4.0497(6) 272.5(13)

• n annealed substrate

PCT 3.8920(6) 4.0187(8) 279.0(9) PCT (Recryst. 1h) 3.8929(2) 4.0230(4) 266.1(11) PCT (Recryst. 2h) 3.8982(2) 4.0227(4) 258.4(9) PCT (Recryst. 3h) 3.9001(4) 4.0228(11) 253.6(29)

PTC film Pt layer Recrystallisation reduces the stress on t h e f i l m , a n d , increases the lattice parameters A n n e a l i n g o f t h e substrate does not introduce significant variations on the structure of the Pt layer

0.01 75 1 m.r.d.

Texture index F2 (mrd2)

R factors (%)

non-treated substrate

Pt 129 RW=13, RB=12

annealed substrate

Pt 199 RW=8, RB=14 Pt (Recryst. 1h) 199 RW=9, RB=20 Pt (Recryst. 2h) 195 RW=9, RB=14 Pt (Recryst. 3h) 222 RW=27, RB=12

Pt layer <111> fibre orientation

Annealing of the substrate, which involves crystal growth, results in an increase of the degree of

• rientation of the Pt layer.

New information on the Pt layer provided by the combined method

Texture

1 m.r.d. 0.01 9.5

Texture index

F2 (mrd2)

non-treated substrate

PTC 5.2 annealed substrate PTC 2.1 PTC (Recryst. 1h) 2.1 PTC (Recryst. 2h) 2.5 PTC (Recryst. 3h) 2.5

PCT film

Effect on the degree of

• rientation of the PCT film

PCT film on untreated substrate Strong <100> orientation

5.8 1 m.rd. 0.04

PCT film on annealed substrate Strong <111> orientation Effect of the annealing of the substrate in the type of texture developed

Si nanocrystalline thin films

broad, anisotropic diffracted lines, textured samples χ = 0° χ = 35°

Anisotropic sizes (Å) Texture parameters Reliability factors (%) Sample d (cm) a (Å) RX thickness (nm) <111> <220> <311> Maximum (m.r.d.) minimum (m.r.d.) Texture index F2 (m.r.d2) RP0 Rw RB Rexp A 4 5.4466 (3)

• 94

20 27 1.95 0.4 1.12 1.72 4.0 3.7 3.5 B 6 5.4439 (2) 711 (50) 101 20 22 1.39 0.79 1.01 0.71 4.9 4.3 4.2 C 7 5.4346 (4) 519 (60) 99 40 52 1.72 0.66 1.05 0.78 4.3 4.0 3.9 D 8 5.4461 (2) 1447 (66) 100 22 33 1.57 0.63 1.04 0.90 5.5 4.6 4.5 E 10 5.4462 (2) 1360 (80) 98 20 25 1.22 0.82 1.01 0.56 5.0 3.9 4.0 F 12 5.4452 (3) 1110 (57) 85 22 26 1.59 0.45 1.05 1.08 4.2 3.5 3.7 G 6 5.4387 (3) 1307 (50) 89 22 28 1.84 0.71 1.01 1.57 5.2 4.7 4.2 H 12 5.4434 (2) 1214 (18) 88 22 24 2.77 0.50 1.12 2.97 5.0 4.5 4.3

001 Inverse Pole Figures

A B C

H

G F E D 111 221 010 001 100 011 101 110 332 443 113 111 max min

a-SiO2 (100)-Si

Amorphous Si-O-N thin films: Electron Density Profiles (S. Banerjee, Calcutta)

EDP SIMS

2 z iq

• z

dz e dz d 1 ) R(q

z

∫

∞ ∞ − ∞

ρ ρ =

Irradiated fluoroapatite (S. Miro, F. Studer, CRISMAT)

• as synthesized
• irradiated 1013 Kr

• 0 5.1012

1013

Crystalline phase A (Å) 9.336(3) 9.377(4) 9.4236(4) C (Å) 6.855(2) 6.891(3) 6.911(1) <t> (Å) 2936(387) 2940(500) 2911(545) <ε> (rms) 0.0025(4) Vol Fraction (%) 100 63 15 "Amorphous phase" A (Å)

• 9.45(2)

9.99(2) C (Å)

• 7.08(2)

7.02(3) <t> (Å)

• 40(4)

24(2)

Conclusions

• a: Texture affects phase ratio and structure determination
• b: Stresses shift peaks then affects structure and texture

determination

• c: Incorrectly determined structure affects texture (go to a)
• Combined analysis may be a solution, unless you can

destroy your sample or are not interested in macroscopic anisotropy ...

• If you think you can destroy it, perhaps think twice
• more information is always needed: local probes ...