空孔團簇缺陷對矽晶體及其奈米線熱/力性質之影響

The effects of vacancy cluster on thermal / mechanical properties of silicon crystals and nanowires

呂啟銘(Qi-Ming Lu)

指導教授 ： 黃培興

國立屏東科技大學/工學院/機械工程系所/碩士(2011年)

https://doi.org/10.6346/NPUST.2011.00238

摘要

近年來半導體產業已經迅速的蓬勃發展起來，其中大部分所使用的材料以矽為主，而材料中可能存在固有缺陷，缺陷對材料本身機械性質仍然有很多的未知因素，因此本研究運用分子動力學研究空孔團簇缺陷對矽奈米線受力學拉伸行為之耦合效應及使用第一原理計算空孔團簇缺陷對矽晶體熱學性質。
研究首先以Tersoff 勢能去探討不同尺寸之空孔團簇缺陷對矽奈米線在各種不同之溫度場、線截面形狀與截面積等條件下之楊氏係數及降伏強度等力學行為之影響；其次以第一原理平面波贋勢法，研究表面侷限與空孔缺陷效應對矽奈米線之能帶結構、能隙及聲子色散關係。
研究結果表明完美以及含空孔團簇缺陷的奈米線皆會隨著線截面積減小與高溫所形成之耦合效應將大幅減小奈米線之降伏強度，圓形截面較方形截面的奈米線的降伏強度高，另外空孔團簇缺陷並未影響奈米線楊氏係數之變化，楊氏係數僅會隨著溫度的上升以及線截面積之減小而減少，此外模擬結果也顯示，熱容會隨著空孔團簇尺寸的增加而有下降的趨勢，當溫度小於150 K以下的低溫時，空孔團簇缺陷對整體熱容量的影響甚小，而隨著缺陷尺寸的增大與溫度升高使奈米晶體熱容降低。

關鍵字

空孔團簇缺陷 ； 矽奈米線 ； 分子動力學 ； 機械性質

並列摘要

In recent decade year, the semiconductor industry has developed rapidly, and the most commonly used semiconductor materials is silicon. However, there may be exist intrinsic defects in materials and the effects of vacancy defects on the mechanical behavior of nanowires are largely unknown. Therefore, this study investigates the coupled effects of various vacancy culster (VC) defects, temperature, wire-shape, and wire cross-sectional area on the mechanical properties behavior of silicon (Si) nanowires (NWs) using molecular dynamics (MD) simulations and calculate the thermal properties of Si crystals using first principles.
In this paper we investigate the influence of VC defects on the tensile stretching behavior of Si-NWs, including Young’s modulus, yield strength, and plastic deformations, were thoroughly studied by MD simulations with Tersoff potential model. The next, the effects of surface confinement and VC defects on the band structure, band gap energy, and phonon dispersion properties were examined using a first-principles plane-wave pseudopotential method.
Simulation results indicates that the coupled effects of VC defect with increasing temperature and decreasing wire cross-sectional area were significantly decreasing the yield strength of Si-NWs and the perfect nanowires are the same. However, the NWs with circle cross sections have higher yield strength than the square cross section at large cross- section size. On the other hand, the Young’s modulus of NWs was decreased with increasing temperature and decreasing wire cross-sectional area, but was independent of VC defects size. Moreover, the heat capacity were decreased with increasing the size of VC defect. As the temperature lower than 150 K, the heat capacity was affected barely with VC defect.

並列關鍵字

vacancy cluster defect ； silicon nanowire ； molecular dynamics simulation ； mechanical properties

參考文獻

[1] Li, S.-Q., Marshall, J. S., Liu, G. and Yao, Q., 2011, “Adhesive particulate flow: the discrete element method and its application in energy and environmental engineering,” Prog. Energy Combust. Sci., Vol. 37, pp. 633-668.

[2] Dirac, A. M., 1958, “The Principles of Quantum Mechanics,” Oxford.

[3] Lew, K. K., Pan, L., Dickey, E. C. and Redwing, J. M., 2003, “Vapor–Liquid–Solid Growth of Silicon–Germanium Nanowires,” Adv. Mat., Vol. 15, pp. 2073-2076.

[4] Duan, X., Huang, Y., Cui, Y., Wang, J. and Lieber, C. M., 2001, “Indium Phosphide Nanowires as Building Blocks for NanoscaleElectronic and Optoelectronic Devices,” Nat., Vol. 409, pp. 66-69.

[5] Cui, Y., Wei, Q., Park, H. and Lieber, C. M., 2001, “Nanowire Nanosensors for Highly Sensitive and Selective Detection of Biological and Chemical Species,” Science, Vol. 293, pp. 1289-1292.