本文選題：稀磁半導(dǎo)體 + 自旋電子器件　； 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：自旋電子器件由于具有體積小,速度快,非易失性等優(yōu)點,可以極大提高信息的處理速度。稀磁半導(dǎo)體作為自旋電子器件中的關(guān)鍵材料,目前已經(jīng)引起了電子學(xué)、物理學(xué)及材料科學(xué)等多學(xué)科研究者的關(guān)注。ZnO基稀磁半導(dǎo)體由于具有性質(zhì)穩(wěn)定、原料豐富、可以實現(xiàn)高濃度摻雜等優(yōu)點,并且在光、電、磁等領(lǐng)域存在眾多優(yōu)異性質(zhì),已經(jīng)成為了稀磁半導(dǎo)體研究的熱門領(lǐng)域,并取得了一定的進(jìn)展。但在眾多的理論計算和實驗研究成果中,仍然存在很多亟需解決的問題,如實驗重復(fù)性差、居里溫度低、磁性起源機(jī)理不明確等。為尋求具有高居里溫度的ZnO基稀磁半導(dǎo)體,本文采用了基于密度泛函理論(DFT)的第一性原理研究方法,計算并討論了Co、Mn單摻雜和共摻雜ZnO基稀磁半導(dǎo)體的磁穩(wěn)定性和磁性起源機(jī)理,并研究了非金屬元素和本征缺陷的引入對Co-Mn共摻雜ZnO的影響。得到研究結(jié)果如下:(1)分別構(gòu)建了2×2×2的Co單摻雜ZnO和Mn單摻雜ZnO超晶胞模型,對它們在五種不同摻雜位置下的構(gòu)型進(jìn)行計算和分析。結(jié)果表明:Co單摻雜ZnO和Mn單摻雜ZnO都不具有室溫鐵磁性。系統(tǒng)的磁穩(wěn)定性與雜質(zhì)元素的摻雜位置有很大關(guān)系,其中Co摻雜ZnO在兩種構(gòu)型下表現(xiàn)出鐵磁性,另外三種構(gòu)型下表現(xiàn)出反鐵磁;Mn摻雜Zn O五種構(gòu)型均表現(xiàn)出反鐵磁性。從能量角度來看,Co摻雜ZnO和Mn摻雜ZnO均趨向于緊密構(gòu)型,即當(dāng)摻雜原子間距離較近時,體系基態(tài)能量更低、結(jié)構(gòu)更穩(wěn)定。(2)根據(jù)摻雜位置的分析結(jié)果,構(gòu)建了緊密構(gòu)型下的Co-Mn共摻雜ZnO模型。對其磁性和電子特性的計算和研究表明:相比于單摻雜體系,Co-Mn共摻雜ZnO表現(xiàn)出了穩(wěn)定的鐵磁性,并且具有遠(yuǎn)高于室溫的居里溫度。其磁性起源主要是Co和Mn的3d電子通過鄰近O原子發(fā)生的交換作用。(3)為研究實際制備中常見的空位缺陷和雜質(zhì)對ZnO基稀磁半導(dǎo)體的影響,本文在Co-Mn共摻雜ZnO體系中引入了空位及非金屬元素的摻雜缺陷。結(jié)果顯示,當(dāng)Co-Mn共摻雜ZnO中引入O缺陷、C元素和N元素后,體系從鐵磁穩(wěn)定轉(zhuǎn)變?yōu)榉磋F磁穩(wěn)定。從而表明在Co-Mn共摻雜ZnO中,O缺陷、C元素和N元素的引入不利于形成室溫鐵磁體,在制備過程中要避免這些雜質(zhì)的產(chǎn)生。Zn空位的引入對于Co-Mn共摻雜ZnO的磁性和居里溫度有明顯的提高。具體表現(xiàn)在:增強(qiáng)了鄰近O原子和Co原子的磁矩,但對Mn原子的磁矩略有削弱。體系自旋劈裂的產(chǎn)生除Co-3d、Mn-3d電子的共同作用外,Zn空位的引入也大大加強(qiáng)了O-2p在費米能級處的自旋劈裂。
[Abstract]:Spin electronic devices can greatly improve the processing speed of information because of its advantages of small volume, high speed and nonvolatile.As a key material in spin electronic devices, dilute magnetic semiconductors have attracted the attention of many researchers in electronics, physics and material science. ZnO based diluted magnetic semiconductors have stable properties and abundant raw materials.High concentration doping can be realized, and there are many excellent properties in the fields of light, electricity, magnetism and so on. It has become a hot field in the research of dilute magnetic semiconductor, and has made some progress.However, in many theoretical and experimental results, there are still many problems that need to be solved, such as poor repeatability, low Curie temperature, unclear magnetic origin mechanism and so on.In order to search for ZnO based diluted magnetic semiconductors with high Curie temperature, the first principle research method based on density functional theory (DFT) is used in this paper.The magnetic stability and magnetic origin mechanism of Co-Mn mono-doped and co-doped ZnO based diluted magnetic semiconductors were calculated and discussed. The influence of the introduction of nonmetallic elements and intrinsic defects on Co-Mn co-doped ZnO was studied.The results are as follows: (1) 2 脳 2 脳 2 Co mono-doped ZnO and mn mono-doped ZnO supercell models are constructed, and their configurations at five different doping positions are calculated and analyzed.The results show that neither ZnO nor mn mono-doped ZnO have room temperature ferromagnetism.The magnetic stability of the system is closely related to the doping position of impurity elements. Co- doped ZnO exhibits ferromagnetism in two configurations, and the other three show antiferromagnetic properties in all of the five Zn-doped Zn-O configurations.From the point of view of energy, both Co doped ZnO and mn doped ZnO tend to be compact, that is, when the doping atoms are close, the ground state energy is lower and the structure is more stable.The Co-Mn co-doped ZnO model with compact configuration was constructed.The calculation and study of the magnetic and electronic properties show that the codoped ZnO exhibits stable ferromagnetism and is much higher than the Curie temperature at room temperature.Its magnetic origin is mainly due to the exchange of 3D electrons of Co and mn through adjacent O atoms. The effect of vacancy defects and impurities on ZnO based diluted magnetic semiconductors is studied.Vacancy and nonmetallic doping defects were introduced into Co-Mn co-doped ZnO system.The results show that the system changes from ferromagnetic stability to antiferromagnetic stability when O defect C and N elements are introduced into Co-Mn co-doped ZnO.It is shown that the introduction of C and N elements in Co-Mn co-doped ZnO is not conducive to the formation of room temperature ferromagnets.In the process of preparation, it is necessary to avoid the introduction of these impurities. Zn vacancies can obviously improve the magnetic properties and Curie temperature of Co-Mn co-doped ZnO.The results show that the magnetic moment of the adjacent O and Co atoms is enhanced, but the magnetic moment of mn atom is slightly weakened.In addition to the co-action of Co-3dGn-3d electrons, the introduction of Zn vacancy in the system also greatly strengthens the spin-splitting of O-2p at Fermi level.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN304

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