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New materials characterization by TEM scanning precession electron diffraction in combination with e-PDF in situ analysis at nanoscale

Monday, March 12, 2018 - 11:00
nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian
Stavros Nicolopoulos, NanoMEGAS SPRL, Brussels, Belgium
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The tremendous impact of SEM based EBSD techniques over the past 20 years demonstrates the value of mapped crystallographic information , which provides insight on processing history, structure-property relationships, interfaces and phase structure with resolution range from 50-10 nm. The development of TEM based- automated crystallographic mapping techniques (ASTAR) in combination with precession electron diffraction (PED) [1,2] has pushed the resolution limit at 1 nm scale. Combination of ASTAR 4D scanning orientation/phase map technique with advanced TEM Cs corrected /FEG instruments over the last 10 years allowed study of various materials such as metals /alloys, minerals , semiconductors and even organic materials. The combination of PED with scanning nanodiffraction enables to measure accurately strain (precision up to 0.01%) with 1-3 nm resolution at semiconductor devices. 
Although all work done on phase and orientation maps has been limited with known crystal phase materials (unit cell and atomic coordinates) there are many problems where we deal with unknown phases. ADT 3D (automatic diffraction tomography combined with precession diffraction) allows 3D reciprocal space reconstruction from tilted ED series (usually every 1 deg) from nanocrystals as small as 20 nm. This way unit cell & structure determination can be obtained by measuring ED intensities from unknown structures [3] where atomic positions can be located with picometer level precision via dynamical refinements [4]. 

The recent application of e-PDF (electron Pair Distribution Function) techniques [5] allows to analyse at local scale Electron Diffraction (ED) patterns even from amorphous materials. e-PDF technique allows to analyse interatomic distances , bonding and possible short/large scale order of nanocrystalline /amorphous materials at nm scale , enabling to monitor in situ solid state reactions, structure of glassy materials, layered thin films quality and amorphous/ re-crystallization studies in semiconductor devices. 
We will present various application examples of PED combination with orientation imaging, ADT 3D and e-PDF studies for studies of materials from characterization of colour pigments in Ancient Roman mosaic glass to high tech semiconductor devices. 
[1] Vincent R & Midgley PA (1994) Ultramicroscopy 53, 271-282 [2] Rauch E.F,Portillo J, Nicolopoulos S. Bultreys D. Rouvimov S. Moeck P. (2010) Zeit fur Krist, 225,103-109 [3] Kolb U, Gorelik T , Kubel C, Otten M, Hubert D (2007) Utramicroscopy , 107, 507-513 [4] Mugnaioli E., Gemmi M, Merlini M , Gregorkiewitz (2016) Acta Cryst B72 , 893-903 [5] T.Egami, S.Billinge Underneath the Bragg Peaks Pergamon vol.16

Host: A. Chuvilin

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