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Recrutement

Stages Master 1 / Master 2

Imaging and control of polar domain walls in ferroelectric materials for high density storage media

Downscaling of memory devices for ultra-high storage densities and low power consumption is a major challenge for post-CMOS electronics in order to implement new functionalities. Domain wall (DW) engineering in ferroic materials is one possible route where the DW rather than the bulk material becomes the active element. The challenge then is to predict and control the nanoscale DW functionality [1]. DWs are transition regions where the changes of the order parameter from one domain to another result in strong gradient effects. Ferroelastic materials can contain a very high density of polar DWs [2] with dipole moments in the wall aligned parallel or antiparallel [3] to the apex and therefore serve as robust, nanoscale functional devices such as memory cells. CaTiO3 is the prototypical non-polar ferroelastic showing DW polarity.

For more information:
Sujet_Walls_CEA_an.pdf

X-ray photoelectron diffraction study of structural phases in epitaxially strained ferroelectric thin films

A fundamental property of ferroelectric (FE) materials is their electrically switchable spontaneous polarization below the Curie temperature, which has driven promising applications of such materials as nonvolatile memory storage devices and sensors. Structural changes in thin films can modify the ferroelectric state [1] and thus the performance of these materials in nanoelectronic devices, chemical sensors or photovoltaic cells. The polarization state may be chemically switched by annealing under oxygen [2] and epitaxial strain can engineer completely new FE phases [3].

X-ray Photoelectron Diffraction (XPD) combines the chemical sensitivity of core level photoemission with local order sensitivity around the emitting atom. The photoemission intensity is measured as a function of angle above the sample [4], giving information on interatomic distances, bond angles and chemical states. It is therefore ideally suited to measure the surface distortions in the atomic structure of epitaxial FE films [5]. IRAMIS has recently installed a new, high angular resolution XPD experiment with fully automatic data acquisition system.

 

For more information: 
Sujet_XPD_CEA_an.pdf

 

Thèses

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Stages Post-Doctoraux

Propositions déposées tout au long de l'année

 

 

 

 

 

 

 

 

 

 

Maj : 13/09/2016 (2017)

 

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