發(fā)布時間：2018-01-09 05:13

  本文關(guān)鍵詞：硅鍺核殼納米線的帶隙漂移和光吸收性質(zhì)的應(yīng)變調(diào)制　出處：《湖南師范大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 核殼納米線 鍵弛豫理論 帶隙漂移 光吸收系數(shù)

【摘要】：作為微納光電子器件領(lǐng)域中一類重要的結(jié)構(gòu)單元,Si/Ge和Ge/Si核殼納米線因其優(yōu)異的物理和化學(xué)性質(zhì)得到了科學(xué)家們的重點關(guān)注。核殼納米線體系與相應(yīng)的塊體材料和單組元納米線不同,它的殼層能使體系內(nèi)載流子發(fā)生分離,容忍更多的無位錯彈性形變,以及為體系表面勢阱態(tài)提供有效鈍化。此外,核、殼原子層之間由于界面失配和熱脹系數(shù)的不同,體系將處于總能極小的自平衡態(tài)。因此,體系的性質(zhì)將受到表面和界面的調(diào)制。從而,從理論的角度澄清界面之間的相互作用機理以及體系性質(zhì)的尺寸和形狀效應(yīng)對核殼納米線的制備和應(yīng)用極為重要。半導(dǎo)體核殼納米線結(jié)構(gòu)的能帶結(jié)構(gòu)、帶隙和光吸收系數(shù)是表征其電子學(xué)和光學(xué)性質(zhì)的重要物理參量。目前的研究中,對此類問題的研究一般采用實驗和計算的方法,而從原子層次的理論模型和相關(guān)理論機制的探索還比較缺乏,特別是對于尺寸和形狀效應(yīng)對體系能帶結(jié)構(gòu)和光吸收性質(zhì)的調(diào)制機制還不清楚。因此,本論文中,基于我們所發(fā)展的原子鍵弛豫理論模型和連續(xù)介質(zhì)力學(xué)理論,我們建立了尺度和形狀依賴的核殼納米線的帶隙漂移和光吸收系數(shù)變化的理論模型。在此基礎(chǔ)上,我們系統(tǒng)研究了Si/Ge和Ge/Si徑向核殼納米線的帶隙漂移和光吸收系數(shù)變化的尺度和形狀效應(yīng),取得的主要進展如下:(1)考慮不同截面形狀(三角、四方、六邊和圓形)的Si/Ge和Ge/Si核殼納米線體系,我們建立了尺度和形狀依賴的帶隙漂移理論模型。通過研究發(fā)現(xiàn):由于體系原子鍵長的自發(fā)收縮和界面晶格的錯配的共同影響,核殼納米線體系處于亞穩(wěn)態(tài),帶隙相對于塊體值發(fā)生藍移;相比于其它截面形狀的納米線體系,三角形截面形狀的體系具有最大的形變勢;(2)研究了Si/Ge和Ge/Si核殼納米線的光吸收系數(shù)的尺度和形狀效應(yīng)。結(jié)果表明:光吸收系數(shù)隨著體系內(nèi)核截面積和外延層厚度的增加而增大;在相同的情況下,四種截面形狀的核殼納米線的光吸收系數(shù)的大小關(guān)系滿足以下關(guān)系:圓形六邊四方三角。
[Abstract]:As an important structural unit in the field of micro-nano optoelectronic devices. Because of their excellent physical and chemical properties, Si/Ge and Ge/Si nanowires have attracted great attention. The core-shell nanowires are different from the corresponding bulk materials and monomorphic nanowires. Its shell can separate the carriers in the system, tolerate more dislocation free elastic deformation, and provide effective passivation for the potential well state on the surface of the system. In addition, the nucleus. Due to the difference of interface mismatch and thermal expansion coefficient between shell atoms, the system will be in a self-equilibrium state with minimal total energy. Therefore, the properties of the system will be modulated by the surface and interface. It is very important to clarify the interaction mechanism between interfaces and the size and shape effect of system properties for the preparation and application of core-shell nanowires. Bandgap and optical absorption coefficient are important physical parameters to characterize their electronic and optical properties. However, the theoretical models and related theoretical mechanisms at the atomic level are still lacking, especially the modulation mechanism of the size and shape effects on the band structure and optical absorption properties of the system. Based on the atomic bond relaxation model developed by us and the continuum mechanics theory, we have established the theoretical models of the band gap drift and the change of optical absorption coefficient of the core-shell nanowires depending on the scale and shape. We systematically study the scale and shape effects of band gap drift and optical absorption coefficient variation of Si/Ge and Ge/Si radial core-shell nanowires. The main progress is as follows: 1) the Si/Ge and Ge/Si core-shell nanowires with different cross-section shapes (triangle, tetragonal, hexagonal and circular) are considered. The theoretical model of scale and shape dependent band gap drift is established. It is found that the core-shell nanowire system is in metastable state due to the spontaneous contraction of the atomic bond length and the mismatch of the interface lattice. The band gap is blue shifted relative to the block value. Compared with other nanowire systems with cross-section shape, the system with triangular cross-section shape has the largest deformation potential. (2) the scale and shape effects of optical absorption coefficients of Si/Ge and Ge/Si core-shell nanowires are studied. The results show that the optical absorption coefficients increase with the increase of the core cross-sectional area and the thickness of the epitaxial layer. Under the same conditions, the optical absorption coefficients of four core-shell nanowires with different cross-section shapes are related to the following: circular hexagonal tetragonal triangle.
【學(xué)位授予單位】：湖南師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.1

【共引文獻】

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本文編號：1400119