Nanoscale Engineering of Ge-based Diluted Magnetic Semiconductors for Room-Temperature Spintronics Application

This chapter gives a systematic investigation of Mn thermal dynamics and kinetics in Mn_xGe_1–x thin film growth. At high growth temperature, Mn preferred to agglomerate to form Mn₅Ge₃ intermetallic compound, whereas the low growth temperature would induce Mn in the form of Mn-rich MnGe nanocolumn. Furthermore, through engineering of the strain in the Ge space layer, MnGe/Ge superlattice can go through a structural transition from nanocolumn to nanodot and finally to nanowell. To search for the ideal diluted magnetic semiconductor (DMS) system, we focus our study on DMS nanostructures, including QDs, nanodisks, and nanomeshes. Inside, not only high T_c (> 400K) but also electric-field control of ferromagnetism can be realized. Based on this extraordinary property, a transpinor device is proposed in which DMS nanostructures are used as the channel for collective spins switching controlled by gate voltage without need of current flow. And thus, it paves a new way for realizing low power-dissipation spin effect transistor.