• PhD position on mechanical properties of nanotwinned gold thin films, Institut PPrime, Poitier, France

    The Physics and Mechanics of Materials Department (PDP and SIMAC teams) at the Institut PPRIME is looking for a PhD on:

    Mechanical properties of nanotwinned gold thin films

    Scientific Context:

    A twin is a portion of a crystal with a particular orientation, for example obtained by a reflection, with respect to a matrix with the same crystalline structure. Twins may appear during plastic deformation, crystal growth or recrystallization. During the last years, nanotwinned materials have been the subject of great interest due to their remarkable mechanical properties: they present large mechanical resistance, ductility and work-hardening capacities. Moreover, they have the same electrical resistivity as coarse grain crystals.

    In this context, the “PtyMet” project aims at characterizing the stress field in nanotwinned thin films, and its impact on physical properties. We will combine experiments (X-ray diffraction and transmission electron microscopy) and simulations (molecular statics and dynamics) and focus on single-crystalline nanotwinned gold thin films. From a numerical point of view, atomistic scale simulations are particularly well adapted tools for these studies. They include key materials properties such as the stacking fault and twin boundary energies, allowing precise descriptions of the defect configurations (e.g. dislocations, grain boundaries, twins). Furthermore, atomic scale simulations and experiments are now working on converging spatial scales. From the experimental point of view, X-ray diffraction can be used to determine the twinned volume (via pole figures) or the stress state in the sample (via Bragg peaks displacement). Moreover, using a coherent X-ray beam allows the characterization of single crystalline defects such as dislocations or twins.

    PhD task:

    Optimization of the deposition conditions is mandatory in order to prepare homogeneous thin films, without other defects than the twins.The films’ microstructure before deformation will be precisely characterized.Simultaneously, atomic scale simulations will be used to establish the elastic strain field associated with different nanotwinned thin film microstructures. Equilibrium conditions will be determined using semi-empirical potentials, that are reliable for gold. The impact of the twins’ density and thickness will be studied.Finally,in-situ tensile tests at synchrotron radiation sources, using both classical and coherent X-ray diffraction,will be performed. This, together with atomic scale simulations,will allow a full characterization, from the atomic to the macro-scale, of the mechanical properties of nanotwinned gold thin films.

    Required skills/qualification:

    The applicant should hold a master degree in solid-state physics or materials science. He/she should show a shared interest in computer simulations and in experimental work. Skills in atomic scale simulations and / or X-ray diffraction will be an asset.


    send a CV and a cover letter to the contacts below.


    Sandrine BROCHARD sandrine.brochard@univ-poitiers.fr

    Pierre GODARD pierre.godard@univ-poitiers.fr

    More information (and a french version) are available in the following document:  these_PhD_PtyMet_nanotwins.pdf »

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