Time：September 21, 2018 (Friday) 14:00-16:00
Place: Room 125,Building 11, Yuquan Campus
Title：The atomic structure of tilt grainboundaries in wurtzite semiconductors
Speaker：Dr Pierre Ruterana Centre deRecherche sur les Ions, les Matériaux et la Photonique (UMR6252)
Inviter：Tian He Researcher
Bio:
Dr PierreRuterana is a Professor in Centre de Recherche sur les Ions, les Matériaux etla Photonique (UMR6252). He has authored/co-authored more than 330 refereedjournal papers, 6 book chapters, 1 edition of scientific book and has made morethan 74 invited presentation in the international conferences. His researchwork has obtained more than 2600 non-self-citations. His research interestincludes Hexagonal symmetry materials(Structural units concept in grainboundaries、Nitridesemiconductors) and Quantitative High Resolution Transmission ElectronMicroscopy(Alloys and heterostructures in Nitride semiconductors for lightemission, Alloys and heterostructuresin Nitride semiconductors for HEMTs、Heteroepitaxy of antimonides for low consumption to autonomouselectronic components).
Abstract:
Since more than 20 years, an extensiveresearch effort has been carried out on wurtzite semiconductors (nitrides andZnO) due to their large direct band gaps which allows the possibility for theproduction of optoelectronic devices (emitters, detectors) from the nearinfrared to the deep ultra violet range. Using high-resolution electronmicroscopy, atomistic calculations, and image simulations, we have investigatedthe atomic structures of the most common extended defects in these materials.In this talk, we shall focus on the a=1/3[11-20] edge threading dislocations.In nitride layers (AlN, GaN, InN), their atomic structure was found to exhibit5/7, 8 or 4 atom cycles. The two first atomic configurations were observed at asimilar frequency for isolated dislocations and low-angle boundaries. The tiltcoincidence grain boundaries around the conventional [0001] growth directionhave been also been studied. The most frequent are made of 5/7 and 8 atomcycles. However, the reconstruction of some boundaries was only possible bytaking into account the occurrence of structural units which include 4-atomring cycles. In nonsymmetric interfaces, a new structural unit made of 5/4/7atom rings constitutes the core of grain boundary dislocations.
