發(fā)布時間：2018-06-20 14:07

  本文選題：關(guān)鍵字 + 非對稱納米線��； 參考：《太原理工大學(xué)》2015年碩士論文

【摘要】：隨著納米技術(shù)的迅速發(fā)展，許多微器件的尺度逐年小型化。當(dāng)器件的特征尺寸達(dá)到納米量級時，無論聲子是以何種方式進(jìn)行熱輸運(yùn)，其熱導(dǎo)率已經(jīng)不再是材料的本質(zhì)屬性，而是依賴于結(jié)構(gòu)和器件的具體形狀、尺寸和邊界。所以，研究幾何形狀、結(jié)構(gòu)參數(shù)等對納米尺度量子結(jié)構(gòu)中的聲子彈道熱輸運(yùn)和非線性熱現(xiàn)象的影響非常重要。然而，在低維納米結(jié)構(gòu)中，，傳統(tǒng)的熱輸運(yùn)理論已經(jīng)不再適用，體系的聲子模及其熱輸運(yùn)性質(zhì)完全由量子力學(xué)原理所支配，從量子力學(xué)原理出發(fā)對系統(tǒng)的聲子模及其熱輸運(yùn)性質(zhì)進(jìn)行研究，是設(shè)計和發(fā)展新型納米器件的重要基礎(chǔ)。本文分別對低溫低維下非對稱納米線的量子化熱導(dǎo)及非對稱彈道四終端納米結(jié)構(gòu)中的熱整流進(jìn)行了研究。 首先，本文研究了低溫下非對稱Z型納米線中彈道聲子熱導(dǎo)的性質(zhì)。其中，簡單介紹了Z型納米線的模型結(jié)構(gòu)。然后，推導(dǎo)出其透射系數(shù)公式，接著討論了透射系數(shù)以及熱導(dǎo)的特性。最后發(fā)現(xiàn)在溫度趨于零的極限下，研究結(jié)果與之前T型納米線的研究結(jié)果相似，即能夠在反對稱納米線中觀察到普適量子化熱導(dǎo)值（2k2B3h），但在其他非對稱納米線中觀察不到。由此可知，納米線左、右引線的橫向尺寸比率a1a2決定了是否能夠觀察到彈道聲子熱導(dǎo)的普適量子值2k2B3h。而且，只有當(dāng)a1a21時，才能測得普適值。 其次，本文對非對稱彈道四終端納米結(jié)構(gòu)中的熱整流性質(zhì)進(jìn)行了理論研究。文章中，展示了非對稱彈道四終端電介質(zhì)納米結(jié)構(gòu)中的熱整流行為，聲子輸運(yùn)的非線性特性，同時分析了熱整流的原因。最后，研究得到了非對稱彈道四終端電介質(zhì)納米結(jié)構(gòu)中產(chǎn)生熱整流的兩個必要條件：1）能量輸入端與能量輸出端之間存在不等的橫向聲子模密度；2）除了具有連接熱庫的輸入端和輸出端以外，還需有連接其它熱庫的終端。而且，只有這兩個條件共同作用才能產(chǎn)生熱整流，其中的任何一個都不能單獨(dú)導(dǎo)致彈道系統(tǒng)的熱整流行為。
[Abstract]:With the rapid development of nanotechnology, many microdevices are miniaturized year by year. When the characteristic size of the device reaches nanometer-scale, no matter how the phonon is transported, its thermal conductivity is no longer the essential property of the material, but depends on the structure and the specific shape, size and boundary of the device. Therefore, it is very important to study the effects of geometry and structural parameters on the thermal transport of acoustic bullet channels and nonlinear thermal phenomena in nanoscale quantum structures. However, in low-dimensional nanostructures, the traditional thermal transport theory is no longer applicable, and the phonon modes and their thermal transport properties of the system are completely controlled by the quantum mechanics principle. Based on the principle of quantum mechanics, the phonon modes and their thermal transport properties of the system are studied, which is an important basis for the design and development of new nanodevices. In this paper, the quantized thermal conductivity of asymmetric nanowires at low temperature and low dimension and the thermal rectification in four terminal nanostructures with asymmetric trajectory are studied. Firstly, the thermal conductivity of ballistic phonons in asymmetric Z-type nanowires at low temperature is studied. The model structure of Z-type nanowires is briefly introduced. Then, the transmission coefficient formula is derived, and the transmission coefficient and thermal conductivity are discussed. At the limit of temperature approaching zero, the results of the study are similar to those of the previous T type nanowires, that is, the universal quantized thermal conductance of 2k2B3hs can be observed in antisymmetric nanowires, but not in other asymmetric nanowires. It can be seen that the transverse size ratio of the left and right leads of nanowires a1a2 determines whether the universal quantum value of thermal conductivity of ballistic phonons can be observed at 2k2B3h. Moreover, only when a1a21 is measured can the universal value be obtained. Secondly, the thermal rectifying properties of four-terminal nanostructures with asymmetric trajectory are studied theoretically in this paper. In this paper, the behavior of thermal rectification and the nonlinear characteristics of phonon transport in asymmetric ballistic four-terminal dielectric nanostructures are demonstrated, and the causes of thermal rectification are analyzed. Finally, two necessary conditions for thermal rectification in asymmetric ballistic four-terminal dielectric nanostructures are obtained: 1) there are different transverse phonon mode densities between the energy input and the energy output. 2) in addition to the input and output terminals connected to the heat storage, there must also be terminals connected to other hot banks. Moreover, only these two conditions can produce thermal rectification, neither of them can lead to the thermal rectifying behavior of ballistic system alone.
【學(xué)位授予單位】：太原理工大學(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(xiàn)】

相關(guān)博士學(xué)位論文 前3條

1 易國軍;低溫下幾種半導(dǎo)體納米結(jié)構(gòu)熱輸運(yùn)性質(zhì)的研究[D];湖南大學(xué);2013年

2 譚仕華;石墨烯納米帶熱電性質(zhì)及其調(diào)控的第一性原理研究[D];湖南大學(xué);2014年

3 郭志霄;微液滴和海藻酸凝膠顆粒在微流控芯片中的應(yīng)用研究[D];武漢大學(xué);2011年

本文編號：2044521