The Study Of The Spintronics Materials Compatible With Silicon: Magnetic Semiconductors

Spintronics is predominant for utilizing the spin and charge degrees of freedom of electrons in the same time, which is regarded as a revolutionary electronics for the future. Materials is the key issue to spintronics, the most potential spintronics materials should possess half-metallic ferromagnetism (HMF), high Cure temperature (TC), good compatibility with mainstream semiconductors technology, and good synthesizability. Semiconductor- spintronics is one key topic of spintronics, which is regarded as the most practical spintronics. Silicon is not only the base of the modern electronics; recent studies show it has potential to be the base of the spintronics. So, the study of spintronics materials compatible with silicon would be very important, which would pave way to silicon-spintronics.Focused on (Zn, Cr)S, (Ga, Mn)P, and MnxSi1-x based magnetic semiconductors (MSs), the magnetism and origin of the magnetism in Zn-chalcogenides (ZnX, X=S, Se, Te), III-IV, and group IV MSs were studied using the first-principles density functional calculations. Moreover, the magnetism and electronic structures of ZrO2 and HfO2 based MSs and the spin injection from these materials into mainstream semiconductors were studied.In chapter two and three, the effect of doping structures on the magnetism and energetics of (Zn, Cr)S and (Ga, Mn)P based MSs was studied. The results indicate that transition metal (TM) impurities are prone to planar clustering into delta-doping structure with enhanced two- dimensional (2D) ferromagnetism (FM). For the delta-doping structures, the energetics and magnetism of the single-, half-, and double-layer delta-doping structures, and the some doping structures close to the delta-doping structure were studied. The results indicate that all studied doping structures of (Zn, Cr)S show robust HMF. For (Ga, Mn)P, only the single-layer and half-layer delta-doping structure of show HMF, while the double-layer delta-doping structure shows anti-FM (AFM). The effect of crystal faces of the matrix semiconductors on the magnetism was studied also. The results indicate that delta-doping on higher symmetric crystal faces (001) shows enhanced 2D FM, while magnetism in lower symmetric crystal faces [(111) and (110)] are deteriorated. The effect of doping structures on the magnetism in MSs can be dictated by the Ligand Field Theory (LFT) and Jahn-Teller effect theory.In chapter four, the effects of delta-doping structures and crystal faces on magnetism in MnxSi1-x were studied. The results indicate that the delta-doping structure in MnxSi1-x (001) show enhanced magnetism than in (111) and (110) faces, only low concentration single-layer delta-doping in MnxSi1-x (001) shows robust HMF, while the magnetism is deteriorated for half-layer and double-layer delta-doing structures. The origin of magnetism in MnxSi1-x using LFT and Jahn-Teller theory was discussed. Unlike (Zn, Cr)S and (Ga, Mn)P, the delta-doping structure of MnxSi1-x only show enhanced ferromagnetic stabilization, while temperature shown HMF is lowered. In the chapter, the magnetism in Si1-xGex and SiC based MSs are also studied. Moreover, the extreme case of the delta-doping structure of Zn-chalcogenides based MSs: TM-sulfides were studied. We find robust HMF in cubic VS, VSe, VTe, CrS, CrSe, and CrTe, and anticipate the potential spintronics application in these ferromagnets.In chapter five, magnetism in the wide band-gap oxids, ZrO2 and HfO2, based MSs and the spin injection from the materials into mainstream semiconductors were studied. The results indicate that effective spin injection into silicon from ferromagnets incompatible with silicon may be realize by using spin-dependent ballistic hot-electron injection scheme. The results indicate that both (Zr, Mn)O2 and (Hf, Mn)O2 not only show HMF at the Fermi lever, but also show HMF at a large range of hot-electron energy. When (Zr, Mn)O2 and (Hf, Mn)O2 is used as the magnetic filtering in the ballistic hot-electron injection scheme, the electrons spin direction can be modulated by modulating the hot-electron energy. The character may be find use in spin direction controllment.The magnetism in ZnS, GaP, silicon, and ZrO2 based MSs with different 3d TM impurities was studied also. The results indicate that the magnetism is substantially determined by the impurities atoms. In chapter two, the effects of the structure of the matrix semiconductor and stress on the magnetism of (Zn, Cr)S based MSs were studied also. The results indicate that the higher the symmetry of the matrix semiconductor, the robust the magnetism. Generally, the stress show important impact on the magnetism in magnetic semiconductors. However, the stress shows little effect on the HMF in cubic (Zn, Cr)S. Moreover, the extreme case of the delta-doping structure of Zn-chalcogenides based MSs: TM-sulfides were studied. We find robust HMF in cubic VS, VSe, VTe, CrS, CrSe, and CrTe, and anticipate the potential spintronics application in these ferromagnets.In chapter two and three, the magnetism in Zn-chalcogenides and III-V based MSs with fair compatibility with silicon was studied. Therein, the results indicate robust HMF in (Zn, Cr)Se, (Ga, Mn)As, (Al, Mn)P, (Al, Mn)As, (Ga, Mn)PxAs1-x, (Ga1-xAlx, Mn)P, and so on. Furthermore, the stidies explored a group of MSs with robust HMF but poor compatible with silicon, such as cubic (Zn, Cr)O, (Zn, Cr)Te, (Ga, Mn)Sb, (Al, Mn)Sb, (In, Mn)Sb, (In, V)N, (In, Cr)N, and so on. The studies indicate potential spintronics application in these MSs.The studies speculate that the delta-doping may be a solution to the controlment of the aggregation trend of the TM impurities in MSs.