Advanced structural and chemical characterization of nanostructures and nanomaterials
To use or develop advanced X-ray techniques for structural and chemical characterization of nanostructures, either ex situ or in situ. Examples are multi-wavelength anomalous X-ray diffraction (MAD), absorption spectroscopy, diffraction anomalous fine structure (DAFS), which are used for measuring strain, composition, short-range atomic order, polarity, ... the experiments are performed mainly at the ESRF and SOLEIL synchrotron radiation facilities.
NON PERMANENT STAFF
Renaud Viennet (PhD student),
Seifeddine Zhiou (PhD student)
University of Zaragoza (Spain) - Prof. M.G. Proietti-Cecconi
CEA-INAC, Grenoble (France) - Dr. B. Daudin
CEA-Leti, Grenoble (France) - Dr. P. Gergaud, Dr. F. Nemouchi
BM2-D2AM at ESRF, Grenoble (France)
Synchrotron SOLEIL, St Aubin (France) - Dr. G. Ciatto, Dr. N. Aubert
Polarity is an intrinsic property of non-centrosymmetrical crystalline structures such as GaN (or ZnO) wurtzite which is determined at the early stage of growth. Therefore, the knowledge of the nanowires (NWs) polarity for different growth parameters, substrate and surface preparations gives, in turn, much information on the NWs growth mechanism. Anomalous diffraction was used to study GaN NWs grown by Plasma-Assisted Molecular Beam Epitaxy (PAMBE) directly on Si substrate. Experimental data clearly shows that as grown-NWs are Nitrogen-polar (the up ended - NWs are Ga-polar). The N-polarity character is believed to be a consequence of the formation of a thin Si(x)N(1-x) layer on the Si surface prior to or at the beginning of GaN growth due to the strong Si – N affinity.
Evolution of the intensity of the 11-22 and 11-2-2 pair of reflections with the energy around the Ga K-edge. Red and blue full circles stand for experimental data obtained from a-NWs (as grown) and u-NWs (upended), respectively. Upper and bottom black lines correspond to simulated curves
K. Hestroffer, C. Leclere, C. Bougerol, H. Renevier, B. Daudin, Polarity of GaN Nanowires Grown by Plasma-Assisted Molecular Beam Epitaxy on Si(111),Phys. Rev. B 84, (2011), 245302.
V. Favre-Nicolin, M. G. Proietti, C. Leclere, N. A. Katcho, M. -I. Richard, H. Renevier, Multiwavelength anomalous diffraction and diffraction anomalous fine structure to study composition and strain of semiconductor nanostructures, Eur. Phys. J. Special Topics 208, (2012), 189.
H. Renevier and M.G. Proietti, Grazing Incidence Diffraction Anomalous Fine Structure in the study of structural properties of nanostructures, in Characterization of Semiconductor Heterostructures and Nanostructures II, G. Agostini, C.E. Lamberti (Eds.), Elsevier, Amsterdam, The Netherlands, (2013). Chapter 8.
C. Leclere, N. A. Katcho, G. Tourbot, B. Daudin, M. G. Proietti, H. Renevier, Anisotropic In distribution in InGaN core-shell nanowires, J. Appl. Phys. 116, (2014), 013517.