Plan : lattices Characterization of thin films and bulk materials using x-ray and electron scattering V. Pierron-Bohnes IPCMS-GEMME, BP 43, 23 rue du Loess, Strasbourg Cedex 2 1) x-ray and electron - matter interaction 2) real lattice and reciprocal lattice in 3D and 2D samples 3) experimental set-ups 4) studies on single crystals 5) multilayers 6) strains measurements using x-ray scattering and TEM 7) powder scattering measurement 8) texture analysis 9) reflectometry 10) chemical analysis 11) short and long range order measurements

Diffractometer (x-rays) 1 primary source 4 secondary beam monochromator 5 detector 2 primary beam monochromator 3 goniometer sample holder 22 2+3 or 3+4: 2 axes diffractometer 2+3+4: 3 axes diffractometer

Diffractometer (x-rays) 5 detector 1 primary source 4 secondary beam monochromator 2 primary beam monochromator 3 goniometer sample holder 22 1 Primary sources: brilliance (Cu-K  )electric power Sealed tubes10 10 counts/s2-3kW Rotating anodes10 11 counts/s18-25kW Synchrotron10 18 counts/s (ESRF) - high voltage cable filament vacuum cathode electrons x-rays glass or ceramics

1 primary source 4 secondary beam monochromator 2 primary beam monochromator 3 goniometer sample holder 22 Diffractometer (x-rays) 2 primary beam monochromators Soller slitshighest flux, limits beam divergence Gobel mirrorhigh flux, monochromatic // beam, div.0.02° 1 bent crystal powder diffraction, monochromatic 2 flat crystals monochromatic, exit in line with incidence 4 crystals (Bartels)highest resolution ( ) + very // beam (0.0014°)

Diffractometer (x-rays) 1 source 4 secondary beam monochromator 5 detector 2 primary beam monochromator 3 goniometer sample holder 22 2 primary beam monochromators Soller slitshighest flux, limits beam divergence Gobel mirrorhigh flux, monochromatic // beam 1 bent crystal powder diffraction, monochromatic 2 flat crystals monochromatic, exit in line with incidence, 4 crystals (Bartels)highest resolution ( ) + very // beam (0.0014°) 1 Si 4 Ge(220) 12”=0.0033° I/3 4 Ge(440) 5”=0.0014° I/75

Diffractometer (x-rays) 1 source 4 secondary beam monochromator 5 detector 2 primary beam monochromator 3 goniometer sample holder 22 3 goniometer + sample holder 1 rotation  powders 3 rotations  single crystals, (4-5 axes diffr.)epitaxied layers    detector support sample holder support cradle

Diffractometer (x-rays) 1 source 4 secondary beam monochromator 5 detector 2 primary beam monochromator 3 goniometer sample holder 22 4 secondary beam monochromator Slits + anti-scatter slitshighest flux, bad angular resolution Soller slitshigh flux, angular resolution ° Gobel mirrorhigh flux, no fluor., good angular resol. high speed investigation of rec. space 2 flat crystals best resolution in angle and energy ( )

Diffractometer (x-rays) 1 source 4 secondary beam monochromator 5 detector 2 primary beam monochromator 3 goniometer sample holder 22 5 detector proportional counters (gaz ionisation), microchanel plates (photomultiplicator), semiconductor detectors (e - -hole pair formation), scintillators (light emission) punctual (1cm x 1cm), linear (10cmx1cm), curved (120°), CCD plates sample monochromator tube curved detector

:  0.1 nm O x-rays incident transmitted A crystal in a diffractometer, what happens ? no diffraction Ewald circle: radius 2  reciprocal lattice of the crystal

O 22 incident diffracted transmitted Bragg law diffraction of the wave

O multicounters :  fixed + 2  varies rapid measurements on powders mapping of the reciprocal space  scan geometries 1 sample surface 22 varies direction fixed in the reciprocal space direction varies

22 Rocking curves : 2  fixed +  varies optimization of the orientation of the specimen coherence length  Q study of textures… fixed O sample surface scan geometries 2  direction varies in the reciprocal space

O  2  :  –  = Cste;   vary together lattice parameter measurement coherence length  // Q mapping the reciprocal space direction fixed   2-   2+  scan geometries 3  sample surface 22   cste sample normal 

O  2  :  vary together lattice parameter  surface for epitaxied films study of planes // surface coherence length  surface structure of powders  surface  scan geometries 4  sample surface 22  2- 

O  2  :  maximum Q Q = 4   surface  scan geometries 5  sample surface 22

 Limitations in the reciprocal space in reflection :   O scan geometries 6 sample surface

Example: L1 0 CoPt fundamental peaks superstructure peaks: z-variant superstructure peaks: x-variant superstructure peaks: y-variant sample position z-variant z x 

Example: L1 0 CoPt 

alignment of a diffractometer 1) the incident beam is // plate 2) the beam crosses the plate center 3) origin of 2  in the incident beam 4) specimen center on plate center 5)  rotation within specimen surface I0I0 I 0 /2  rotation center

Resolution in x-ray diffraction range in the reciprocal space where the intensity is integrated due to the entry and exit slits wavelength spread analyzor Ge(440) mono- chromator Ge(440)

Electron diffraction LEED (low energy electron diffraction) energy = eV → crystal surface Omicron fluorescent screen grids

Electron diffraction: RHEED (Reflection High Energy Electron Diffraction) RHEED intensity oscillations (01) spot measured during the growth of a GaAs(100)-(2x4) surface at E = 12.5 keV with k 0 //[110]. Scheme of RHEED diffraction. shadow sample fluorescent screen full planes half full planes Construction of the diffraction conditions with the Ewald sphere. electrons RHEED image of CoPt deposited by MBE

Electron diffraction: TEM (Transmission Electron Microscope) 1000kV 120kV 2m

EDX EELS TEM Transmission Electron Microscope

≈ nm : fine for crystallography ! wavelength E (eV)

Sources Richardson law: i = AT 2 exp(-  /kT) metal | vacuum

Column difficult optic many aberrations Resolution >>

:  nm O Electron diffraction in TEM incident Ewald sphere

Laue zones Experimental pattern on gold

Example : CoPt/Pt/MgO prepared at 680K Diffraction in plane-view e-e- z-variant z x → 3 growth directions [110](001)//[110](001) O. Ersen Thesis, Strasbourg,

Example : CoPt/Pt/MgO prepared at 680K Diffraction in plane-view e-e- z-variant z x → 3 growth directions O. Ersen Thesis, Strasbourg, 2002

Dark field image showing the different grains in CoPt/Pt/MgO Grains b+d O. Ersen Thesis, Strasbourg, 2002

Dark field image showing the different grains in CoPt/Pt/MgO Grains b order O. Ersen Thesis, Strasbourg, 2002

Dark field image showing the different grains in CoPt/Pt/MgO Grains d O. Ersen Thesis, Strasbourg, 2002

Dark field image showing the different grains in CoPt/Pt/MgO Grains c O. Ersen Thesis, Strasbourg, 2002

[Co 6 nm/Mn 0.4 nm] 12 conventional image

[Co 6 nm/Mn 0.4 nm] 12 diffraction A B C ABAB… ACBACB… ABCABC… Co+Mn Ru [111]fcc [0001]hcp twin A. Michel, Thesis, Strasbourg, 1995

Ru hcp Co fcc twinned Co fcc Co hcp Ru hcp Co hcp [Co 6 nm/Mn 0.4 nm] 12 epitaxied on Ru TEM and X-ray diffraction A. Michel et al, Eur. Phys. J. B (2001).

Ru hcp Co fcc twinned Co fcc Co hcp Ru hcp Co hcp internal standard [Co 6 nm/Mn 0.4 nm] 12 epitaxied on Ru zz   z/sin  radius R 22  z sin2  /sin    z sin2  /Rsin  sample surface / / / / /

Contrasts in TEM Bright field with transmitted beam contrast : defects (strains) + absorption dislocations precipitates

concentration values and profiles Example : precipitates at grain boundaries + inside the grains (different sizes) Chemical analysis:

high resolution Guinier-Preston zones In Al-Cu4% HRTEM along [001] Cu-rich plane

high resolution: ordered CoPt cross section A B O. Ersen Thesis, Strasbourg, 2002

high resolution: ordered CoPt cross section regular black and white contrasts epitaxial strains interface fringes ordered phase ? A B Dislocation in MnPt (Borme, thesis, Grenoble 2006) O. Ersen Thesis, Strasbourg, 2002

high resolution: image simulations HRTEM images simulated using the EMS programme for a CoPt disordered fcc phase, along [100]. The objective defocalization varies with -10 nm steps. The thickness step (1.9 nm) corresponds to 5 elementary cells. 0–70 1.9nm 15.2nm specimen thickness objective defocalization O. Ersen Thesis, Strasbourg, 2002

high resolution: image simulations HRTEM images simulated using the EMS programme for a CoPt L1 0 ordered phase (z- variant), along [100]. The objective defocalization varies with -10 nm steps. The thickness step (1.9 nm) corresponds to 5 elementary cells. 0–70 1.9nm 15.2nm specimen thickness objective defocalization O. Ersen Thesis, Strasbourg, 2002

high resolution: image simulations HRTEM images simulated using the EMS programme for a mixing of L1 0 ordered and disordered CoPt phases (z-variant), along [100]. The objective defocalization varies with -10 nm steps. The proportion step is 14.5%. 0–70 ordered disordered disordered phase proportion objective defocalization O. Ersen Thesis, Strasbourg, 2002

GaAs observed along [110] Defocalization: -60nm to -140nm Specimen thickness: 11nm to 27 nm res.htm

Digitally processed images from the sample [Co 6 nm/Mn 0.4 nm] 12 HRTEM image Inverse FT using the [1011]hcp Inverse FT using the [111]fcc Inverse FT using the [111]fcc-t Mn A. Michel et al, Eur. Phys. J. B (2001).