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Physics Seminar

Selective area epitaxy of nanowires and networks: GaAs, Zn3P2 and Ge

Speaker: Anna Fontcuberta i Morral (EPFL)
Date: Wednesday 8 June 2022
Time: 15:00
Venue: Zoom

Nanowires are filamentary crystals with a diameter tailored at nanoscale dimensions. The small footprint of freestanding nanowires provides advantages from the epitaxial point of view, as it relaxes the requirement of polarity and lattice matching. From the bottom up point of view, freestanding nanowires have been obtained mainly by the selective area epitaxy and by the vapor-liquid-solid method, VLS [1,2]. Selective area epitaxy, SAE, consists in the restricted growth on non-masked regions of a substrate. The mask consists of a material on which growth precursors will not stick at the growth temperature, such as SiO2 or SiNx. It allows for the creation of both free-standing and horizontal nanowire and networked structures. The latter, have attracted recently a lot of attention as they provide a path to integrate nanowire structures and networks directly on a device structure in a scalable manner.
In this talk we will explain how selective area epitaxy can be used to obtain nanowire networks as well as complex heterostructures [3-5]. We will compare the mechanisms in III-Vs, Ge and Zn3P2 as well as the envisioned applications. Finally, we will outline how selective area growth can even provide a path for the creation of high quality textured Zn3P2 thin films, providing a path for the use of this earth abundant absorber in photovoltaics [6-8].

References
[1] P.C. McIntyre, A. Fontcuberta i Morral Materials Today Nano, 9 100058 (2020)
[2] L. G√ľniat, P. Caroff, A. Fontcuberta i Morral, Chem. Revs. 119, 8958 (2019)
[3] M. Friedl et al Nano Lett. 18, 2666-2671 (2018)
[4] M. Friedl et al Nano Lett. 20, 3577-3584 (2020)
[5] V.G. Dubrovskii et al Crystal Growth & Design 21, 4732-4737 (2021)
[6] S. Escobar Steinvall et al. Nanoscale Horiz 5, 274 (2020)
[7] S. Escobar Steinvall et al. Nanoscale Adv 3, 326 (2021)
[8] S. Escobar Steinvall et al ACS Energy Mater. (2021); https://doi.org/10.1021/acsaem.1c02484

Short bio: Prof. Anna Fontcuberta i Morral PhD, Full Professor in Materials Science and Engineering and in Physics, associate Vicepresident for Centers and Platforms at EPFL. She is member of the EPFL-WISH foundation and former president, foundation whose goal is to support female students on accomplishing their professional dreams. Anna studied physics at the University of Barcelona. She then moved to Paris where she obtained a PhD in Materials Science from Ecole Polytehcnique (France). She performed a postdoc at CalTech with Prof. Harry Atwater, with whom she also co-founded the start-up company Aonex Technologies. After a brief period as CNRS researcher at Ecole Polytechnique, she moved to TU Munich as a group leader. She has been professor at EPFL since 2008. Among the awards she has received are the Marie Curie Excellence Grant, ERC Starting Grant, the SNSF-backup schemes Consolidator Grant, the EPS Emy Noether prize and the Polysphere prize for teaching at EPFL.