Chemically functionalized germanene for spintronic devices: a first-principles study

Abstract

We have carried out first-principles calculations to explore various chemically functionalized germanene nanomaterials as two-dimensional spintronic devices. The germanene functionalized with O on one side and H on the other side is a ferromagnetic metal, and the phenomenon of negative differential conductance is observed. Moreover, we construct a spin-filter device from it, and about 15% spin filter efficiency is achieved in its ground state by using finite bias. The germanene semi-functionalized with a methyl (–CH₃) group is a ferromagnetic semiconductor with a small direct bandgap, and it has highly spin-polarized electronic and transport properties. We proposed that a spin-valve nanodevice with a giant magnetoresistance of up to 10⁷% can be obtained from the semi-methylated germanene nanostructure by introducing an achievable magnetic field to stabilize its metal-like ferromagnetic state. Our findings could be helpful for practical applications of two-dimensional germanane-based nanomaterials in spintronic devices in the future.