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Reference : UMR137-PIESEN-004
Workplace : PALAISEAU
Date of publication : Tuesday, January 05, 2021
Scientific Responsible name : pierre seneor/bruno dlubak
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 February 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Spintronics is a paradigm focusing on spin as the information vector in fast and ultra-low-power non-volatile devices such as the new spin-transfer-torque Magnetic Radom Access Memory (MRAM). Beyond its widely distributed applications, spintronics aims at providing more complex architectures and a powerful beyond CMOS solution from storage to quantum information. The recent discovery of graphene, and other 2D materials such as hexagonal boron nitride (h-BN) or dichalcogenides (WS2...), has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices.
Among those new materials, Black phosphorus (BP) has attracted an explosive interest since 2014 as it displays major properties for (opto-)electronic devices: (a) high hole and electron mobilities in thin layers exfoliated BP (about 3000 cm2/Vs) and (b) high ON/OFF current ratio (about 105) in a transistor configuration with ambipolar characteristics. Additionally, the bandgap of BP is predicted to be widely tuneable in relation to the number of stacked layers and remain direct from the bulk to the monolayer. This recent focus on ultra- thin BP has opened novel exciting opportunities in terms of performances for spintronics devices. Thanks to the natural low spin-orbit coupling of phosphorus, BP is expected to present highly efficient spin information transport, similarly to graphene  but with the addition of a band gap. This difference with graphene is fundamental for the implementation of spin manipulation schemes and the experimental realization of a spin gate.
However, the key issue for BP devices has been its degradation under atmospheric conditions. While the mechanism has been recently understood  this still remains a clear problem for applications. Crucially, we very recently developed an in-situ approach to circumvent the issue of degradation under atmospheric conditions . By passivating the BP without exposing it to air we achieve protection down to the monolayer with 1nm Al2O3. Interestingly, this layer can play the role of the tunnel barrier required for efficient spin injection [2,5].
Hence, we want to take advantage of this key development, well ahead of current state of the art, to explore the fabrication and characterization of spintronics devices with the new BP platform. The PhD will have two main axes: (i) the development of fabrication methods for the realization of spin valves (ii) the characterization in terms of spin transport properties.
1. Zatko et al ACS Nano 13 14468 (2019), Piquemal et al Nat Com 11, 1 (2020), Review : Piquemal et al J.Phys.D 50 203002 (2017) 2. Dlubak et al. Nature Phys. 8, 557 (2012); Seneor et al. MRS Bulletin 37, 1245 (2012)
3. Favron, Gaufres et al. Nature Mat. 14, 826 (2015)
4. Galceran et al. APL 111 243101 (2017), Kern et al APL 114, 053107 (2019)
5. Jaffres et al PRB 82, 140408 (2010)
The Unité Mixte de Physique CNRS/Thales is a joint public/private laboratory hosted in Thales' French central research laboratory (Thales Research and Technology) in Palaiseau. The laboratory hosts researchers from the CNRS, Université Paris-Saclay and Thales.
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