Advanced Electron Microscopy (LEMMA)

The LEMMA group is mainly involved in the characterization of materials and nanostructures at a sub-nanometer scale. For many years it has been involved in developing and using High Resolution Transmission Electron Microscopy (HRTEM) for applications in the study of interfaces at the atomic scale. The last 5 years have witnessed a huge evolution of the thematics of the group, as well as of its organization. The investigation of nanomaterials requires the development of new characterization methods and tools. For that purpose, LEMMA develops or optimizes new techniques related to TEM and medium energy ion scattering (MEIS) in order to give information on the structural and chemical properties with the better resolution, but also to probe other physical properties of the materials (electrical, magnetic …).

 

The main evolution of the group comes from its implication in the creation of the Nanocharacterisation center (PFNC) in 2006 at Minatec with two others partners, CEA Léti and Liten. LEMMA is part of both the electron microscopy competence center and the Ion scattering competence center of PFNC. Thanks to a strong investment effort, this unique platform gathers state of the art equipments. In 2005, a new Transmission Electron Microscope FEI-Titan became available, which is equipped with new technologies such as optical aberration correctors and a biprism for electron holography. Moreover, this center creates a new dynamic between the people coming from different laboratories motivating new collaborations. With the new equipments available on this center, LEMMA has been able to develop novel methods to address important issues related to nanomaterials and nanostructures. We mainly focused on four new topics, always with the purpose to get quantitative information on structural, chemical and physical properties :

i) atomic imaging by Scanning TEM : we were able for instance to detect and count isolated dopant atoms in a matrix,

ii) magnetic field mapping, this thematic being mainly motivated by the Grenoble environment on spintronic and nanomagnetism research,

iii) electric field mapping, so as to address the issues of doping in electronic devices or in semiconductor nanowires,

iv) strain mapping by diffraction techniques, such as convergent beam electron diffraction (CBED) or nanodiffraction.

Moreover, PFNC also acquired a new MEIS equipment in 2007. This unique surface characterization technique gives access to chemical information and strain profiles within ultra-thin layers. For instance, MEIS has been used to map strain fields in GaN/AlN superlattices and quantum dots.

 

LEMMA performs developments on two main characterization tools: Electron Microscopes and MEIS. We have in the lab or have preferential access thanks to the PFNC to:

  • TEM: JEOL 4000EX, 3010 (GIF filter), 2010FEF (omega filter), FEI-TITAN (equipped with probe cs corrector, biprism, GIF tridiem). These equipments are used for atomic imaging, and mapping of the chemical composition (EELS and EDX) or of electric, magnetic or strain fields;
  • 2 Focused ion beam systems (FEI-Strata dual beam and ZEISS “Cross beam”), which are used for TEM specimen preparation as well as nanomanipulation and nanofabrication in collaboration with other labs of INAC;
  • 2 Scanning Electron Microscopes (SEM ZEISS-ultra plus and Hitachi 5500 equipped with a FEG gun).
  • One 400 keV Medium Energy Ion Scattering equipment.
 

Last update : 02/20 2017 (256)

 

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