Materials Science and Engineering

Biography

Biography: Henri Jaffres

Abstract

Molybdenum disulfide has recently emerged as a promising two- dimensional semiconducting material for nano-electronic and spintronic applications. However, the demonstration of an electron spin transport through ferromagnetic source and drain connecting a semiconducting MoS₂ channel remains challenging. Here, the author will present the experimental evidence of the electrical spin-injection and spin-detection in the conduction band of a multilayer MoS₂ semiconducting channel using a two terminal spin-valve configuration geometry. A magnetoresistance around 1% have been observed through a 450 nm long, 6 monolayer thick MoS₂ channel with a Co/MgO tunneling spin injector and detector. It is found that keeping a good balance between the interface resistance and channel resistance is mandatory for the observation of the two-terminal magnetoresistance. Moreover, the electron spin-relaxation is found to be greatly suppressed in the multilayer MoS₂ channel with an in-plane magnetization and spin-polarization. The long spin-diffusion length (approximately 235 nm) could open a new avenue for spintronic applications using multilayer transition metal dichalcogenides. In this talk, corollary to experiments, I will particularly emphasize on the mechanism of spin-injection at interfaces between a spin-polarized tunnel junction and a semiconductor channel, homogeneous or not. The latter can be composed of several regions, uniformly doped or depleted to form a Schottky contact and possibly location of a conduction made by hopping. I will extend the conditions for spin-injection from a spin- polarized ferromagnetic source into a Schottky contact on the ground of the experiments observed with success on MoS₂ systems.

Figure 1: Multilayer MoS₂-based lateral spin-valve device. (a) Optical image of the device with the multilayer MoS₂ flake on 100 nm SiO₂/Si(nþ þ) substrate, the E1, E2, E3 and E4 indicate the four Au/Co/MgO electrodes. (b, c) AFM measurement (in tapping mode) focused on the MoS₂ channel between E1 and E2 electrodes. The thickness of MoS₂ is determined by the Gaussian distribution of pixel height in the square region in b. (d) Schematics of the lateral spin-valve device. The multilayer MoS₂ serves as a spin transport channel, and two Au/Co/MgO electrodes are used to inject spin (Vds) and measure the current (Ids). A back-gate voltage (Vg) between the substrate and one top contact is used to modulate the carrier density in MoS₂.

Recent Publications:

1.A Fert, J M George, H Jaffrès, R Mattana (2007) Title. IEEE transactions on electron devices 54:5.

2.A Fert, H Jaffrès (2001) Title. Phys. Rev. B 64:184420.

3.M Tran, H Jaffrès, C Deranlot, J M George, A Fert, A Miard, A Lemaître (2009) Title. Phys. Rev. Lett. 102: 036601.