自組裝分子膜之力學特性分析與實驗研究

Analysis and experimental studies of mechanical characterization of self-assembled monolayers

方俊男(Chun-Nan Fang)

指導教授 ： 方得華

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2008年)

摘要

本文藉由分子動力學模擬自組裝分子膜吸附金薄膜表面特性，並探討奈米尺度壓痕和刮痕的變形機制及機械特性。以緊束法勢能來描述金薄膜間作用力；自組裝分子膜的結構相當複雜，利用粗晶化的模型簡化下就可以單純地以一顆顆分子來呈現為等效的分子鏈。分子鏈內部廣用勢能以描述鍵長、鍵角及扭轉角交互作用；分子鏈的非鍵結力和分子鏈吸附金薄膜採用Lennard Jones勢能。模擬結果發現；在壓痕過程中，隨著壓痕越深時，最大負載力與黏著力也隨之增加。壓痕區域隨著壓痕深度越深變的越來越明顯，而在持壓階段發生鬆弛力現象。在刮痕過程中，隨著刮痕越深時，摩擦力與正向力也隨之增加。刮痕區域隨著刮痕深度越深，導致整條鏈有脫落情形，而摩擦係數也隨刮痕深度來增加。最後，將實驗與模擬結果做一系列比較分析，探討自組裝分子膜吸附金薄膜之機械與摩擦特性。

關鍵字

自組裝分子膜；分子動力學；粗晶；奈米壓痕；奈米磨潤學

並列摘要

The nanoindentation and nanoscratch of self-assembled monolayers (SAMs) chemisorbed on an Au surface are investigated by molecular dynamics (MD). This study uses the tight-binding second-moment approximation (TB-SMA) potential to describe the interaction force between Au and Au atoms. Due to the complexity of the structure of SAMs, the coarse grain equivalent scheme is treated as a single-spherical molecule to an equivalent SAMs chain. For the description of the intramolecular interactions in a SAMs chain, bond stretching potential, bending potential, and the torsion potential were adopted. The non-bonded and SAMs chemisorbed on an Au surface was adopted Lennard-Jones potential. The MD simulation is accomplished by utilizing the efficient list rule. The results showed that when the indention depth of the sample increased were observed during indentioning process, the maximum load and the adhesion were increased. The indention areas showed obvious, and the force relaxation took place at the holding process. The results showed that when the scratch depth of the sample increased were observed during scratching process, the friction force and the normal force were increased. The scratch areas showed break away, and the frictional coefficient can be defined as a value of the friction force and the normal force. The MD results will be compared with the experimental results.

並列關鍵字

Self-assembled monolayer ； Molecular dynamics ； Coarse grain ； Nanoindentation ； Nanoscratch

參考文獻

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