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Séminaire PLUM

Jeudi 14 février à 16h00
Salle Erwin Bertaut, F418

Orateur : Andreas Zerr, Laboratoire des Sciences des Procédés et des Matériaux, CNRS, Villetaneuse
"High pressure synthesis of novel binary nitrides and examination of their properties:challenges and benefits"


Pressure shifts equilibrium of chemical reactions of elemental metals with nitrogen towards formation of compound s with cations having a higher oxidation state when compared with the counterparts at atmospheric pressure. Applying high pressure – high temperature (HP-HT) techniques we discovered dense nitrides of the group 14 elements having spinel structure, γ-A3N4 (where A=Si, Ge, Sn) [1], as well as of the group 4 and 5 elements having Th3P4 structure (c-M3N4 where M=Zr or Hf) and U2S3 structure (η-Ta2N3), respectively [2,3]. Laser heated diamond anvil cell (DAC) is the most suitable HP-HT technique for the synthesis of pure binary nitrides but the samples are small, typically <0.1 mm in size. Availability of a gas-loading apparatus for filling of the reaction volume in a DAC with condensed nitrogen, preferably at 3000 bar, is a prerequisite. Large volume presses permit synthesis of macroscopic samples (1-5 mm in size) but special efforts are needed to control the products stoichiometry, to limit contamination with oxygen and exclude a reaction with the capsule material. Today we know th at some of the discovered binary nitrides have been deposited as films or coatings [4,5]. Experimental methods used to determine structure and composition of the HP-HT products will be presented and the related challenges discussed. We applied advanced techniques of laser ultrasonics and nanoindentaion testing to measure reliably mechanical properties of small samples of <0.2 mm in size [6-8]. Because the examined samples were porous, we developed an approach permitting evaluation of the porosity contribution and obtaining of elastic moduli for the dense materials [6]. Information about electronic structure of the novel nitrides was obtained using the synchrotron based soft X-ray- and UV-vis-IR spectroscopy. The spinel nitrides and their solid solutions such as γ-(Ge1-xSnx)3N4 as well as c-Zr3N4 and c-Hf3N4 were found to have electronic band structures making them highly suitable for optoelectronc (LEDs) and photovoltaic applications with the overall performance approaching or exceeding that of the (Ga,In)(As,N) family members [9,10].

1. A. Zerr, G. Miehe, G. Serghiou, M. Schwarz et al., Nature 400, 340 (1999) ; A. Zerr, R. Riedel, T. Sekine, J. E. Lowther, W.-Y. Ching and I. Tanaka, Adv. Mater. 18, 2933 (2006).
2. A. Zerr, G. Miehe and R. Riedel, Nat. Mater. 2, 185 (2003).
3. A. Zerr, G. Miehe, J. Li, D. Dzivenko, V. Bulatov, H. Höfer et al, Adv. Funct. Mater. 19, 2282 (2009).
4. M. Chhowalla and H. E. Unalan, Nat. Mater. 4, 317 (2005).
5. T. Maruyama and T. Morishita, J. Appl. Phys. 77, 6641 (1995).
6. A. Zerr, N. Chigarev, R. Brenner R., D. Dzivenko and V. Gusev, Phys. Status Solidi-RRL 4, 353 (2010).
7. A. Zerr, N. Chigarev, O. Brinza, S. Nikitin et al., Phys. Status Solidi-RRL 6, 484 (2012).
8. J. Bourguille, O. Brinza, F. Tétard, S. Nikitin and A. Zerr, EPL 111, 18006 (2015).
9. T. D. Boyko, A. Hunt, A. Zerr and A. Moewes, Phys. Rev. Lett. 111, 097402 (2013).
10. L. Museur, A. Zerr A. and A. Kanaev, Sci. Rep. 6, 18523 (2016).

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