以實驗法測定鍺奈米線線徑與機械性質之關係

Abstract

在奈米科技的潮流下，各式各樣新穎的奈米材料接二連三的出現。但面對這些嶄新且近乎一無所知的奈米材料，其性質測定成了最重要的課題。而在眾多的研究中，有不少的資料指出材料的彈性模數將隨著尺寸的縮小而有著大幅度的變化。 本文利用奈米科技中最重要的工具之一－原子力顯微鏡對最尖端的奈米材料－鍺奈米線進行機械性質的測定。使用的技術分別是奈米壓痕技術及三點彎曲測試法。 此兩項技術雖然看似相差很遠，但最基本的觀念皆是針對待測材料施以壓力，使之變形。而原子力顯微鏡便兼具了奈米世界的眼睛及手指兩項功能，使這兩項實驗方法能夠實行。而在實際操作上，需先針對原子力顯微鏡本身進行一連串的校正，讓所得數值儘量接近事實。而之後便針對鍺奈米線進行壓印，並對所得線型進行分析計算，即可得到材料之模數。兩種方法最大的差別即在於分析方法的不同。在大量的實驗後，兩種實驗方法得到了類似的結果，也就是隨著鍺奈米線的線徑漸縮，其模數逐漸上昇，由小至大可差到七倍之多。但兩套實驗方法所得結果仍有一段不小的差異，原因可能在於實驗動作上的誤差及試料製備上的瑕疵。故此實驗方法尚須進一步的改進。 雖然結果不一定如人意，但本文導入的兩套針對奈米材料之機械性質測定法，相信對於後續之材料研究有所影響。

In the tide of nanotechnology, all kinds of nano-materials appeals. Face of the brand new and clueless nano-materials, properties measuring plays the most important role in research. Within the great deal of researches, there are many evidences that the modulus will vary greatly with the reduction of dimensions. We’ll use AFM, the most important tool in nanotechnology, to measure the mechanical properties of germanium nanowires, the most advanced nano-material. We’ll use “nano-indentation” and “three point bending test” to do the work. It seems that the two techniques are definitely different, but the basic concepts of them are the same, to press the material and make it changing the shape. AFM plays two roles in nano-world, eyes and fingers, to make the experiment methods to be done. In practice, we need to calibrate several parameters of the AFM, to make the results close to the truth. After the calibration, we indent the Ge nanowires and analyze the curves from indentation to get the modulii. The most difference between two methods is analyzing method. After a large quantities of experiments, two methods got similar results, the modulus rises with the radius reduces. But the values of them are discrepancy. The reasons may comes from the inaccuracy of experiment and the blemishes of sample production. So the experiment methods still need further improvement. Although the results are not as perfect as predict, the two mechanical properties measuring methods used here will influence the coming material research.