非故意掺杂碳对ZnMnO:N磁性影响的实验与理论研究

利用金属有机源化学气相沉积技术, 通过改变受主掺杂源和导入氢气并提高生长压力来逐步抑制C的办法, 在蓝宝石上外延了Mn, N共掺ZnO薄膜. X射线衍射显示所有样品都具有良好的单轴取向. ZnMnO:N样品的Raman光谱中C元素相关的振动模明显消失. 同时van der Pauw法Hall效应测量表明, 通过逐步对C的抑制, 样品由n型导电转变成p型导电, 这主要是由于C与N形成复合体取代O位(CN)O, 具有最低形成能且充当浅施主. 对N, Mn共掺ZnO晶体的第一性原理模拟计算显示了N, Mn共掺ZnO的态密度在Fermi能级处存在较强的自旋极化, 表明N 2p电子与Mn 3d电子之间存在较强的p-d相互作用, 形成磁性束缚激子产生磁矩. 一旦引入C后, C, N形成复合体取代O位, 导致体系磁性减弱或者消失. 模拟计算结果与实验表征分析结果一致表明: 对于Mn, N共掺ZnO薄膜样品, 引入C与N形成复合体取代O位, Mn, N共掺ZnO薄膜磁性减弱或消失. 因此, Mn 3d电子与N 2p局域束缚的电子形成的磁性束缚激子决定了Mn, N共掺ZnO薄膜室温铁磁信号的产生.

Experimental and theoretical studies on the influence of unintentionally doped carbon on magnetic properties in ZnMnO:N

Mn-N co-doped ZnO film on sapphire substrate is fabricated by metal-organic chemical vapor deposition method with changing the acceptor-doped source and importing the hydrogen and increasing the pressure to suppress carbon (C) approach gradually. X-ray diffraction displays the strong C-axis orientation. Raman sepectrum is employed to analyze vibration modes related to C elements. Hall measurements on the samples by van der Pauw method reveal the transition from n-type to p-type after suppression of C, which is possible due to the complex of (CN)O acting as a shallow donor. The first principles simulation calculation for Mn and N codoped ZnO crystals has been perfermed, and the total density of states reveals the strong p-d interaction and magnetic moment existing in the Mn and N codoped ZnO. The introduction of the complex of (CN)O, causes the p-d interaction to disappear and the magnetic moment to reduce even disappear. Therefore, the formation of magnetic bound polaron of Mn 3d electronics and N 2p local bound electronic determines the magnetic interaction effect, which can be explained from the theoretical predication on the Mn 3d and N 2p ferromagnetic (hole) coupling on the ferromagnetism.