Spin transport and relaxation in graphene, functionalized-graphene & graphene-TMD heterostructures

Graphene is a one-atom-thick carbon material, known for its exceptional electronic properties, which can be utilized in the future electronics industry. Also, it has shown a great potential for carrying the spin-angular momentum of electron up to long distances, making it useful in the field of ‘spintronics’ where electron-spins serve as information carriers. In this thesis, I study two fundamental problems in graphene-based spintronic devices: first, which factors affect the spin-transport in graphene and second, how to control the spin-current in graphene. In order to address these issues, we perform spin-transport experiments in various device architectures. We find that magnetic impurities are detrimental to the spin-transport, which we confirm by measuring the spintronic properties of graphene, decorated with magnetic porphyrin molecules. Alternatively, we also perform spin-dependent noise measurements in graphene and find that the spin-noise magnitude is higher by three-to-four orders than the charge noise magnitude. We attribute this behaviour to impurities scattering the electron-spins more severely than electronic-charge. In order to control the spin-current in graphene, we combine graphene with another 2D-material, tungsten disulfide (WS2), and fabricate graphene-WS2 heterostructures. We find that spin-transport is greatly suppressed in graphene which is in contact with WS2 due to the enhancement of spin-orbit coupling in graphene. This property can also be controlled via external electric-field. The obtained results can be utilized to improve the performance of future graphene-based spintronic-devices and to demonstrate the first graphene-based spin-transistor.