MIME: Multiple Interferometry and Moirés with Electrons
Research project selected under the 2013 call for proposals
Principal Investigator :
Aurélien MASSEBOEUF ()
CEMES (NMAT)
Type of project : Collaborative Project
Partner team(s) :
CEMES (MC2)
Date (start/end) : 2014 - 2017
Magnetic flux radiated in the front of a Hard Disk Drive (perpendicular anisotropy) writing head (Seagate © ). Imaging is here provided by a Moirés Holographic method that used an addition of various states of the writing pole and coils (by tuning the exciting current) within the same acquired image. The obtained contrast is revealed by the use of holograms instead of standard images, that were obtained using Transmission Electron Microscopy in Holographic mode.
Image size is 150 x 150 nm.
Abstract
The main purpose of the MIME project is to access new sensitivity at the nanoscale by developping new forms of imaging techniques. Some of the informations that are actually missing in the nanomaterial science should then be revealed by the use of such new methods : detailed magnetic field generation of a hard drive writing head, strain field on single silicon nanoparticles embedded within the dielectric matrix of optoelectronic devices, electrostatic field as well as charge density distribution of next generation electron sources and dynamics of the strain under capillary forces are some of the material concerns at the origin of the MIME project.
These techniques can be joined under a concept of a mix between Moirés and Interferences. At first, Moirés are the result of an interference bewteen two networks that can be of various form. Moirés can appear in various condition, from the superposition of textiles to the observation of a striped shirt on the TV including the observation of a wire netting through another one. Moirés are in fact the apparition of an extra network from the superposition of two other ones. Secondly, Interference is the essential concept underlying the Electron Holography method in used in Transmission Electron Microscopes. Such a technique uses the coherence of the electron source to produce holograms that are carrying an hidden information : the phase of the electron wave. This phase can display an information relative of the fields present in the object under consideration (electric, magnetic or strain field).
Merging this two concepts will enable us to observe with a better sensitivity the field in the above discussed material problems. Two techniques will be developped (and labelled) within this project. First one relies on the capacity of producing Moirés directly from electron hologram by adding various states within a single image. These states will « interfere » one each other to produce new kind of Moirés onto the holograms (see Figure) baring a direct quantification of the magnetic or electric field in and around devices in operation. Second one is linked to the basic defintion of Moires as the main idea is to probe defects within a network using another reference network placed inbetween the electron source and the sample under study. Here, the specificity in our approach is to rely on electron optic to produce Moirés with networks ranging in the nanoscale (0,00000001 cm), separated by a distance of roughly 10 cm.