奈米線機電性質量測方法之研究

Nanomechanical and Electrical characterization Measurements for Nanowires

林家弘(Chia-Hung Lin)

指導教授 ： 章明

中原大學/工學院/機械工程研究所/博士(2009年)

https://doi.org/10.6840/cycu200901086

摘要

奈米線、奈米帶和奈米棒等一維奈米材料之應用為目前最有發展潛力與被關注的研究主題，主要是由於奈米材料的樣式相當多，且其力學特性與宏觀尺度下有極大的差異性。過去相關之研究多偏重在材料的製備技術，目前製備技術已經愈來愈成熟，但當奈米材料在進行構裝時，經常會在接縫處斷裂而造成故障，甚至破壞了組裝好的奈米結構，因此需要更深入的了解奈米材料之基本結構及其材料特性，奈米材料的機電特性亦成為當前極為關鍵且重要的課題。
本研究係通過自行研發一套放置於掃描式電子顯微鏡真空腔內部的多自由度奈米機械操作平台對奈米材料的機電性質做量測，此平台整合了三組X、Y、Z及θ軸精密平台、壓電陶瓷、馬達控制及人機介面等，經由電腦直接下指令進行控制，具有在立體空間中進行奈米加工及測試的功能，並對不同之奈米線材，進行單根奈米線抽離、拉伸實驗、挫屈實驗及電性測試，以測得材料之楊氏係數及導電性質等材料特性，並且利用切薄片的方式測量奈米線截斷面積與形狀來提高其準確度。
經實驗測試與分析結果驗證，一維奈米線突顯了非等向性材料在不同的方性上對於材料性質的影響，以硫化鋅奈米線來說，在米勒指數[100]上之楊氏係數為12.3GPa較米勒指數[111]方向的楊氏係數35.9GPa小了2.9倍，結晶硼奈米線其米勒指數[111]的楊氏係數190GPa大於其米勒指數[100]方向的72.7GPa約2.77倍。在一維材料的導電性上也因體積縮小而限制了電子傳導的路徑而造成電阻率的提升，由實驗所測得的金奈米線其電阻率2.07×10-4Ωm，雖因接觸電阻而與巨觀下金之電阻常數2.4×10-8Ωm有極大差異為，但也觀測到一維材料側向電阻率隨直徑的增加而有漸減的關係變化。

關鍵字

截面積 ； 奈米線 ； 奈米操作器

並列摘要

Nanostructures materials have stimulated broad attention in the past decades because of their potential applications ranging from nano composite to nanoelectromechanical systems (NEMS). The small dimensions of such materials impose a tremendous challenge for experimental studies of their intrinsic mechanical, electrical and other device related properties.
This study describes about the development of a mechanical manipulation system that can perform five degrees of freedom nanomechanical manipulation inside a scanning electron microscope (SEM). Experiments are carried out by constructing a precise machining platform integrated with picomotors, linear stages and monolithic-silicon-based tips which is generally used in atomic-force microscope (AFM). This integrated system can easily manipulate the atoms in a workpiece inside a SEM. The platform consists of three translational stages of resolution 30 nm along XYZ axis direction and one rotational stage having angular resolution 1 mrad.
This manipulation system is used to monitor three dimensional nano manipulation processes and study the mechanical behavior of ZnS nanobelt, crystalline boron and Au nanowires. Electron beam induced deposition (EBID) method is used to clamp nanowire to the AFM tip inside the SEM vacuum chamber. The mechanical properties of the nanowires are observed by applying continuously increasing load on it. SEM image is analyzed to observe the deformation of the nanowire during tensile and buckling test. Transmission electron microscope (TEM) and atomic force microscope (AFM) are used to measure the cross-sectional areas of the nanowires. The Young’s moduli of the boron and ZnS nanowires have been measured to be (190 ± 15) GPa, and 12.3GPa respectively. The manipulation system has been used to measure the resistivity of a Au nanowire and determined to be 2.07×10-4Ωm. It is observed that the resistivity of nanowire decreases with the increase in diameter.

並列關鍵字

cross-sectional ； nanowire ； nanomanipulator

參考文獻

1. D.M. Eigler and E. k. Schweizer, “Positioning single atoms with a scanning tunneling microscope,＂ Nature, Vol.344, pp.524, 1990.

2. S. Iijima, “Helical microtubules of graphitic carbon,＂ Nature, Vol.354, pp.56, 1991.

3. H.J. Qi, K.B.K. Teo, K.K.S. Lau, M.C. Boyce, W.I. Milne, J. Robertson, and K.K. Gleason, “Dtermination of mechanical properties of carbon nanotubes and vertically aligned carbon nanotube forests using nanoindentation,＂ Journal of Mechanics and Physics of Solids, Vol.51, pp.2213, 2003.

4. M.J. Treacy, T.W. Ebbeaen, and J.M. Gibson, “Exceptionally high Young’s modulus observed for individual carbon nanotubes,” Nature, Vol.381, pp.678-680, 1996.

5. E.W. Wong, P.E. Sheehan, and C. M. Lieber, “Nanobeam mechanics: elasticity,strength, and toughness of nanorods and nanotubes,” Science, Vol.277, pp.1971-1975, 1977.