Microstructure and Ferromagnetism of Mn_0.05Ge_0.95 Quantum Dots/Graphene Heterostructures for Spintronic Devices

Mn x Ge 1– x quantum dots (QDs), with a high Curie temperature and superior magnetic properties, have significant application and research values for spintronic devices for high-density memory devices. However, the lattice mismatch between silicon and germanium leads to the formation of intermetallic precipitates, thereby constraining the utilization of Mn x Ge 1– x QDs in spintronic device applications. In this work, we report the first preparation of Mn 0.05 Ge 0.95 QDs/graphene heterostructures by ion beam cosputtering. Growth time-dependent QD density and formation of nanoislands were investigated systematically, indicating a transition of n-type to p-type conductivity in the sample with increasing deposition time, and high hole transport properties were observed in samples with quantum dots. A Curie temperature of 342 K observed in Mn x Ge 1– x QDs is higher than room temperature. Circularly polarized light-induced spin currents and linearly polarized light-excited currents were confirmed in the QD samples. The relationship between circularly polarized light-induced spin current signals and incident angles was examined. Our research offers a cost-effective method to integrate Mn x Ge 1– x low-dimensional materials with two-dimensional materials, achieving high Curie temperatures above room temperature along with favorable hole transport properties, thereby facilitating further studies on spintronic devices.