本文選題：硅烯 + 摻雜�。� 參考：《清華大學》2016年博士論文

【摘要】：硅烯是一種新型的二維納米材料,無論是理論上還是實驗上都已證實了穩(wěn)定孤立單層硅烯的存在。鑒于硅烯納米材料具有很高的應用價值,所以已有許多研究工作關(guān)于探究硅烯材料的各種性質(zhì),其中最為引人關(guān)注的一種性質(zhì)為磁性。在本文的工作中,我們采用第一性原理計算方法研究金屬原子替位摻雜硅烯體系的結(jié)構(gòu),電子性質(zhì)和磁性質(zhì),以及在外電場或拉力作用下金屬原子摻雜硅烯體系特殊的磁性變化。我們系統(tǒng)的研究了過渡金屬原子(Sc-Zn)嵌入硅烯單空位體系的結(jié)構(gòu),電子性質(zhì)和磁性質(zhì)。研究發(fā)現(xiàn),除Zn原子外其它9種金屬原子(Sc-Cu)摻雜硅烯體系都會呈現(xiàn)兩種穩(wěn)定的結(jié)構(gòu),不同金屬原子摻雜硅烯的結(jié)構(gòu)會有不同的對稱性,即使同種金屬原子摻雜硅烯所產(chǎn)生的兩種結(jié)構(gòu)也可能具有不同的對稱性。且計算發(fā)現(xiàn)有些金屬原子摻雜硅烯體系所具有的磁矩大小會不同于其摻雜石墨烯的磁矩。我們對過渡金屬原子替位摻雜硅烯體系施加外電場研究其電子性質(zhì)和磁性質(zhì)的變化。對于高濃度Fe原子摻雜硅烯體系,在外電場的作用下會呈現(xiàn)獨特的開關(guān)效應。對于低濃度的Fe或Cr原子摻雜硅烯體系,在外界電場的作用下同一種金屬原子摻雜硅烯的兩種構(gòu)型呈現(xiàn)完全不同的磁性變化,特別是Fe原子摻雜硅烯體系其中一種結(jié)構(gòu)的磁性隨外電場的變化可以類似的看作“磁電二極管”。無論是高濃度還是低濃度Fe和Cr原子摻雜硅烯體系,隨著外電場的變化都會有一段近線性變化區(qū)域。外界拉力也可以影響硅基納米材料磁性質(zhì)。對Cr和Fe原子替位摻雜硅烯體系施加各向同性雙軸拉力和單軸拉力,可以觀察到摻雜體系顯著的磁矩變化。當各向同性雙軸拉力達到某一個小的臨界值時,Cr和Fe原子摻雜硅烯體系會有一個快速地由低自旋態(tài)到高自旋態(tài)(4μB)的轉(zhuǎn)變。在一定的單軸拉力作用下,Fe原子摻雜硅烯體系也會由一個幾乎無磁態(tài)快速轉(zhuǎn)變到一個較高的磁性狀態(tài)(2μB),而Cr原子摻雜體系在外界單軸拉力作用下會逐漸增大到4μB左右的高自旋態(tài)。研究發(fā)現(xiàn)Fe和Cr原子摻雜硅烯體系磁矩的變化與外界拉力的大小和作用方式有密切的關(guān)系。
[Abstract]:Silyene is a new two-dimensional nano-material, which has confirmed the existence of stable monolayer silicon monolayers, both theoretically and experimentally. In view of the high application value of silicene nanomaterials, many researches have been done on exploring the various properties of silicene materials, among which the most attractive one is magnetism. In our work, we use first-principle method to study the structure, electronic and magnetic properties of substitution doped silicene system. And the special magnetic changes of metal atom doped silicene system under the action of external electric field or tensile force. The structure, electronic and magnetic properties of the transition metal atom (Sc-Zn) intercalated silicene single vacancy system have been systematically studied. It has been found that there are two stable structures in the system of nine metal atoms (Sc-Cu) except Zn atoms, and the structures of different metal atoms have different symmetries. Even the two structures produced by doping silicon with the same metal atom may have different symmetries. It is also found that the magnetic moment of some metal atoms doped with silicene is different from that of graphene. We applied an external electric field to the transition metal atom substituted doped silicene system to study the changes of its electronic and magnetic properties. For high concentration Fe doped silicene system, there is a unique switching effect under the action of external electric field. For low concentration Fe or Cr doped silicene system, the two configurations of the same metal atom doped with silicene show completely different magnetic changes under the action of external electric field. In particular, the magnetic properties of one of the structures of Fe doped silicene system can be regarded as magnetoelectric diodes similarly with the change of external electric field. Both high and low concentrations of Fe and Cr atoms doped in silicene system have a near linear range with the change of external electric field. The magnetic properties of silicon-based nanomaterials can also be affected by external tensile force. When isotropic biaxial tensile force and uniaxial tensile force are applied to the substitution doped silicene system with Cr and Fe atoms, significant magnetic moment changes can be observed in the doped system. When the isotropic biaxial tension reaches a small critical value, there will be a rapid transition from low spin state to high spin state (4 渭 B). Under the action of uniaxial tension, the Si-doped system of Fe atom also changes rapidly from an almost non-magnetic state to a relatively high magnetic state (2 渭 B), while the Cr atom doping system increases to 4 渭 B under the external uniaxial tension. The left and right high spin states. It is found that the variation of magnetic moment of Fe and Cr doped silicene system is closely related to the magnitude and mode of external tension.
【學位授予單位】：清華大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O469

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