Cu掺杂ZnO稀磁半导体磁电性能影响的模拟计算

在Cu重掺杂量摩尔数为0.02778–0.16667的范围内, 对ZnO掺杂体系磁电性能影响的第一性原理研究鲜见报道. 采用基于自旋密度泛函理论的平面波超软赝势方法, 用第一性原理计算了两种不同Cu单掺杂量Zn_1-xCu_xO (x=0.02778, 0.03125)超胞的能带结构分布和态密度分布. 结果表明, 掺杂体系是半金属化的稀磁半导体; Cu掺杂量越增加、相对自由空穴浓度越增加、空穴有效质量越减小、电子迁移率越减小、电子电导率越增加. 此结果利用电离能和Bohr半径进一步获得了证明, 计算结果与实验结果相符合. 在限定的掺杂量0.02778–0.0625 的条件下, Cu单掺杂量越增加、掺杂体系的体积越减小、总能量越升高、稳定性越下降、形成能越升高、掺杂越难. 在相同掺杂量、不同有序占位Cu双掺ZnO体系的条件下, 双掺杂Cu-Cu间距越增加, 掺杂体系磁矩先增加后减小; 当沿偏a轴或b轴方向Cu–O–Cu相近邻成键时, 掺杂体系会引起磁性猝灭; 当沿偏c轴方向Cu–O–Cu相近邻成键时, 掺杂体系居里温度能够达到室温以上的要求. 在限定的掺杂量0.0625–0.16667的条件下, 沿偏c轴方向Cu–O–Cu相近邻成键时, Cu 双掺杂量越增加, 掺杂体系总磁矩先增加后减小. 计算结果与实验结果变化趋势相符合.

Effects of Cu doped ZnO diluted magnetic semiconductors on magnetic and electrical performance from simulation and calculation

At present, the effects on the magnetic and electrical properties of Cu heavily doped ZnO with the mole amount of Cu being in a range of 0.02778-0.16667 are rarely studied by first-principles. Therefore two models for Zn_1-xCu_xO supercells (x=0.02778, 0.03125) are set up to calculate the band structures and density of states by using the plane-wave ultrasoft pseudopotential based on the spin-polarized density functional theory. The calculation results indicate that the doped systems are degenerate semiconductors, and they are semimetal diluted magnetic semiconductors. As the doping amount of Cu increases, the relative concentration of free holes increases, the effective mass of holes decreases, the electron mobility decreases and the electronic conductivity increases. These results are validated again by the analysis of ionization energy and Bohr radius, and they are consistent with the experimental data. As the doping amount of single-Cu increases from 0.02778 to 0.0625, the volume of doping system decreases, the total energy increases, the stability decreases, the formation energy increases and doping is more difficult. As the same concentration and the different doping modes for double-Cu doped, the magnetic moment of doping system first increases and then decreases with the increasing of spacing of Cu-Cu; while the bonds of nearest Cu–O–Cu lie along the a-axis or b-axis, the magnetic moment of doping system disappears; while the bonds of nearest Cu–O–Cu lie along the c-axis, the Curie temperature reaches a temperature above room temperature. As the doping amount of double-Cu increases from 0.0625 to 0.16667, the total magnetic moment of doping system first increases and then decreases, while the bonds of nearest Cu–O–Cu lie along the c-axis. The calculation results are consistent with the experimental data.