Presentation on theme: "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,"— Presentation transcript:
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, 67034 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
diffracted intensity a powder = small grains + all directions present with the same probability all planes diffract when 2 is convenient example: L1 0 CoPt polarisation integration + structure multiplicity 1 crystal absorption factor Monochromator intensity: for powder no integration in n
multiplicity? = number of equivalent peaks in the reciprocal space (multiplies the probability to observe this peaks) Examples: cubic lattice: tetragonal lattice Texture: some directions are more present than in a random distribution, in powders: faceted grains can be placed preferentially with the facets // surface in films, a single crystal substrate can induce a texture (epitaxy) an amorphous substrate can also induce a texture (high compacity planes parallel to the surface) Taking into account all the corrections, the peak intensities are compared to determine if there is a texture or not texture ?
absorption correction volume in the beam H: total thickness depends on if not in geometry (curved counter) length of trajectory in and out: x (- ( ) depends on if in geometry z
flat rocking curve ? limitations of the beam limitation of incident beam ? limitation of exit beam ? high : L I < L E sin small : L I > L E sin high : L D < L E sin small : L D > L E sin
precise measurement of a lattice parameter for perfect ajustments and without absorption: Bragg law 2d sin = n effect of a sample not located at the center of the goniometer: Rsin(2 ’- ) = Rsin(2 ) + z R cos z z/Rcos 2d sin = n → d sin + d cos =0 zz radius R: detector position 2’2’ sample surface → d/d= - cotg → d/d= - z / Rsin is minimum for /2 (return peaks) to eliminate it: plot as a function of 1 / sin extrapolated at 0 / / / / / / / / / / / / / / / / / 22 Rsin(2 ’ ) Rsin(2 )
precise measurement of a lattice parameter Displacement of Bragg peak due to absorption: where with absorption: without absorption: g
powders (polycrytalline samples) in TEM Example: magnetite in powder Selected-area electron diffraction patterns of a sputtered sandwich (Co3 nmRu1.05 nmCo3 nm) (two printings of the same pattern).
simulation with CarIne: powder XRD example: FePd ordered =0.154056nm
simulation with DIFFRACT: powder TEM example: FePd ordered 002 022 ordered disordered