µLaue diffraction and excited luminescence in nitrides optoelectronics: physics, operando, serial crystallography

The Laue microdiffraction instrument (µLaue), installed at the European Synchrotron (ESRF) in Grenoble (BM32 beamline), is unique in Europe and probes the matter by diffracting a polychromatic X-ray beam of a few hundred nanometers. The acquisition of the Laue diffraction diagram is very fast and allows scanning the samples with high precision to get the structural parameters of mono or polycrystalline materials in terms of orientation, crystallographic lattice parameters and lattice strains. The possibility to measure the emitted visible and near IR light excited from X-ray (called XEOL for X-ray Excited Optical Luminescence) has been recently added to this instrument. The acquisition of XEOL spectrum is synchronized to the diffraction pattern collection so that to measure on the same sample’s location.

The PhD subject consists in participating in the development of new ESRF experiments with our team (improvement of light collection and setup), performing materials science physics and optimizing data processing using image analysis algorithms, intelligent Laue diagram recognition and artificial intelligence. A specific focus will be laid on the determination of strain fields/rotations, and the nature of defects in nitride materials (In,Al,Ga-N, especially µLEDs) and its correlation with the emission properties. This new analysis method will allow the systematic treatment of a large amount of data by “serial crystallography” (term used in biology). We will study nitride materials that are of paramount industrial importance in optoelectronic and high-power devices.

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