本文選題：Bi系材料 + 能帶結(jié)構(gòu)��； 參考：《中國礦業(yè)大學(xué)》2015年碩士論文

【摘要】：Bi2X3(X=Se,Te,S)是VB-VIB族中三種重要的半導(dǎo)體材料,具有一系列優(yōu)異的特性。本文通過第一性原理系統(tǒng)化地研究了這三種材料塊體、薄膜和表面及相關(guān)結(jié)構(gòu)摻雜的電子結(jié)構(gòu),對其晶體結(jié)構(gòu)和由晶體結(jié)構(gòu)變化導(dǎo)致的電子結(jié)構(gòu)變化有了一定程度的研究。本文的主要研究內(nèi)容包括:首先,對R-3m結(jié)構(gòu)Bi2Se3材料的電子結(jié)構(gòu)進行了計算分析,結(jié)果表明:其純凈塊體為直接帶隙半導(dǎo)體,帶隙值約為0.32e V,與實驗值吻合較好,Se原子和Bi原子的p軌道態(tài),構(gòu)筑了它們的價帶和導(dǎo)帶;單“五層”(quintuple layer,QL)薄膜表現(xiàn)出間接帶隙特性,帶隙值約為0.91e V,態(tài)的構(gòu)成與塊體類似;摻入Pb后,與Pb近鄰的Se(1)層原子排列發(fā)生變化,變?yōu)镾e(1/)層,Pb摻雜對能帶結(jié)構(gòu)的影響主要是通過Se(1/)層來實施的,其自身原子態(tài)的影響有限;Bi的6s態(tài)對價帶頂有調(diào)制作用,該調(diào)制使得塊體保持直接帶隙半導(dǎo)體的特征;而對于薄膜,Bi的6s態(tài)的對價帶頂處態(tài)的影響顯著降低,這時的弱調(diào)制導(dǎo)致它們的價帶頂偏離導(dǎo)帶底位置,帶隙的性質(zhì)也從直接帶隙變化為間接帶隙;單QL薄膜同樣表現(xiàn)出間接帶隙特性,帶隙值約為0.24e V,其價帶和導(dǎo)帶主要由p態(tài)構(gòu)成,摻雜Al原子后帶隙表現(xiàn)出11.5%的降低,態(tài)的構(gòu)成并未發(fā)生重大調(diào)整;平面應(yīng)變下薄膜電子結(jié)構(gòu)的變化,主要體現(xiàn)在帶隙值隨應(yīng)變比例的線性改變。其次,對R-3m結(jié)構(gòu)Bi2Te3材料電子結(jié)構(gòu)進行了計算分析,結(jié)果表明:Bi2Te3塊體材料和Bi2Se3類似,表現(xiàn)出直接帶隙特征,帶隙值約為0.177e V,計算結(jié)果表明自旋軌道耦合作用對電子結(jié)構(gòu)無重大影響。而單QL薄膜表現(xiàn)出明顯的間接帶隙特征,帶隙值約為1.031e V。雙QL薄膜相較于單QL薄膜其間接帶隙特性減小,帶隙值約為3.122e V;平面應(yīng)變下薄膜電子結(jié)構(gòu)的變化,主要體現(xiàn)在帶隙值隨應(yīng)變比例的線性改變,不同厚度薄膜斜率不同。最后,對Bi2S3材料的電子結(jié)構(gòu)進行了計算分析,結(jié)果表明:Pnma結(jié)構(gòu)Bi2S3塊體屬于間接帶隙半導(dǎo)體,但價帶頂位置不明顯,帶隙值約為1.198e V;Bi2S3塊體中在摻雜Se、Te后電子結(jié)構(gòu)未有太大變化,主要是由于摻雜原子與S原子性質(zhì)近似,其帶隙值分別為1.186e V和1.001e V,差別主要來自于不同原子對周期性勢場調(diào)整的不同;而Bi2S3(R-3m結(jié)構(gòu))塊體表現(xiàn)出直接帶隙特征,帶隙值約為1.046e V,這也為實驗上的探索提供了參考。
[Abstract]:Bi2X3 XSe TeSs is one of the three important semiconductor materials in the VB-VIB family, which has a series of excellent properties. In this paper, the doped electronic structures of these three kinds of bulk materials, thin films, surfaces and related structures have been systematically studied by first principles. The crystal structure and the electronic structure changes caused by the crystal structure changes have been studied to a certain extent. The main contents of this paper are as follows: firstly, the electronic structure of R-3m Bi2Se3 material is calculated and analyzed. The results show that the pure bulk is a direct bandgap semiconductor. The band gap value is about 0.32e V, which is in good agreement with the experimental values of p orbital states of se atom and Bi atom, and their valence band and conduction band are constructed, while the single "five layers" quintuple layer QLL film exhibits indirect band gap characteristics, the band gap value is about 0.91e V, and the composition of the state is similar to that of the block. After the addition of Pb, the atomic arrangement of the adjacent Sean1 layer of Pb changed, and the effect of Pb doping on the energy band structure was mainly carried out by the Se1 / 1) layer. The influence of its own atomic state on the valence band top was limited by the 6s state of Bi. The modulation enables the bulk to retain the characteristics of direct band gap semiconductors, while the effect on the valence band top states of the 6s state of the thin film Bi decreases significantly, and the weak modulation results in their valence band top deviating from the bottom of the conduction band position. The properties of the band gap also changed from the direct band gap to the indirect band gap, and the band gap value of the single QL thin film was about 0.24 EV, the valence band and the conduction band were mainly composed of p states, and the band gap after doping Al atoms showed a decrease of 11.5%. The changes of electronic structure of the thin film under plane strain are mainly reflected in the linear change of band gap value with strain ratio. Secondly, the electronic structure of R-3m Bi2Te3 material is calculated and analyzed. The results show that the ratio Bi2Te3 block material is similar to Bi2Se3 and shows direct band gap characteristics. The band gap is about 0.177e V. the calculated results show that the spin-orbit coupling has no significant effect on the electronic structure. However, the single QL thin films exhibit obvious indirect band gap characteristics, with a band gap value of about 1.031 EV. Compared with single QL thin films, the indirect band gap characteristics of double QL thin films are reduced, the band gap value is about 3.122 EV, and the electronic structure of double QL thin films under plane strain is mainly reflected in the linear change of band gap value with strain ratio, and the slope of different thickness films is different. Finally, the electronic structure of the Bi2S3 material is calculated and analyzed. The results show that the Bi2S3 block is an indirect band gap semiconductor, but the valence band top position is not obvious. The band gap value is about 1.198 e / v ~ (2) Si _ (2) S _ (3). The main reason is that the doped atom is similar to the S atom, its band gap values are 1.186e V and 1.001e V, respectively, the difference mainly comes from the difference of the adjustment of the periodic potential field between the different atoms, while the Bi2S3(R-3m structure) block shows the direct band gap characteristic, and the band gap value of the doped atom is 1.186e V and 1.001e V, respectively. The band gap value is about 1.046 EV, which provides a reference for experimental exploration.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN304

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本文編號：1812955