Spin-orbit torques and photocurrents in 2D materials

While conventional electronics rely on the electron charge as information carrier, using another intrinsic property of the electron, its spin, offers promising ways to further improve information storage technologies. However, the key hurdle lies in gaining precise control over the electron spin. Currently, both electrical and optical methods are being explored to achieve this control.

This thesis delves into the realm of spintronics and optoelectronics, focusing on the effects observed in layered two-dimensional (2D) materials called transition metal dichalcogenides (TMDs). These materials are particularly well-suited for this purpose due to their direct bandgap in atomically thin layers and strong spin-orbit coupling, which is advantageous for spintronic and optospintronic effects.

The initial section of the thesis addresses spintronic effects, specifically the spin-orbit torque (SOT) in TMD/ferromagnetic bilayers. Notably, our study on WSe2/permalloy devices reveals a lack of clear dependence on WSe2 thickness for SOTs, suggesting an interfacial origin. Additionally, we observe the presence of SOTs in a device with a single ferromagnetic layer, highlighting the importance of studying reference samples for accurate determination of the SOT strength.

Turning to the optoelectronic aspect of TMDs, our exploration uncovers that the Schottky barrier at the MoSe2-metallic contacts interface induces additional polarization-dependent photocurrents. Furthermore, we demonstrate that modifying the crystal structure of MoTe2 locally enhances the optoelectronic performance of TMDs based devices.

This thesis provides important steps for the integration of 2D materials in future spintronic and optoelectronic devices.