原子力顯微鏡術應用於混合自組裝單分子膜之奈米尺度摩擦性質定量研究

The Characterization of Nanoscale Friction Properties of Mixed Self-Assembled Monolayers by Atomic Force Microscopy

黃祖緯(Tsu-Wei Huang)

指導教授 ： 曾繁根 ； 錢景常

國立清華大學/原子科學院/工程與系統科學系/碩士(2006年)

摘要

本篇論文中，展示如何利用原子力顯微鏡(Atomic force microscope, AFM)的奈米尺度解析能力，量測樣品表面的摩擦性質，配合配合J. E. Sader [1]的正向作用力校準與R.W. Carpick [2~3]的側向作用力校準方法，定量計算摩擦力(Friction Force)與摩擦係數(Friction Coefficient, μ)，並嘗試以B. Bhushan [4] 提出的原子力顯微鏡探針與樣品表面的接觸行為計算式，進一步分析不同表面處理與樣品材料性質造成的表面物理與化學現象。
研究中，比較親疏水角(Contact Angle)、黏附作用 (Adhesion)、摩擦作用(Friction)等巨觀與微觀尺度現象量測，應用在研究混合直鏈硫醇(Alkanethiol)自組裝單分子膜(Self Assembly Monolayers, SAMs)表面處理效果的探討。以瞭解自組裝單分子膜表面修飾的基本特性，配合接觸力學的理論，印證混合自組裝單分子膜所發生的群聚現象。
實驗結果顯示，混合不同鏈長的直鏈硫醇分子膜，摩擦係數比單一種直鏈硫醇分子膜要來的高，與群聚現象造成局部粗糙度(Roughmess)較大的推測相符合。配合多點彈性接觸的摩擦係數展開式，從混合長鏈分子比例與摩擦性質趨勢中可得到初步的印證。當長鏈分子與短鏈分子以1:1比例相混合，摩擦係數將略小於3:1或1:3比例之混合自組裝單分子膜，推測混合比例與造成群聚區域的大小有關。

關鍵字

原子力顯微鏡 ； 摩擦力顯微鏡 ； 自組裝單分子膜 ； 直鏈硫醇

並列摘要

In this paper, atomic force microscopy has been employed to investigate the surface roughness of mixed self-assembly monolayers (SAMs) with different mixing ratios in nano scale. The combination of Sader’s normal force and Carpick’s lateral force calibration methods were utilized to calculate the friction forces and friction coefficients. The results were also modified by considering B. Bhushan’s model on surface contact properties in physical or chemical aspects.
Through the measurement of contact angles, adhesion forces, and friction forces on alkanethiol SAMs (C5 and C9) with different mixing ratios, the friction force is larger with mixed SAMs than that of pure SAMs, suggesting the contribution of surface roughness on friction force. The mixing ratios also affect the friction force, and the minimum friction appears in the mixing ratio 1 to 1, indicating the different cluster formation in different mixing ratios. Further study is still undergoing to in detail investigate the size, distribution and density of those SAMs clusters under different mixing conditions.

並列關鍵字

Atomic Force Microscopy ； Friction Force Microscopy ； Self-Assembled Monolayers ； Alkanethiol

參考文獻

[1] B. Bhushan, Springer Handbook of Nanotechnology, Springer (2004).

[2] B. Bhushan, Modern Tribology Handbook Volumes I & II, CRC Press (2000)

[3] C. P. Green, H. Lioe, J. P. Cleveland, R. Proksch, P. Mulvaney and J. E. Sader, “Normal and torsional spring constants of atomic force microscopy cantilevers,” Rev. Sci. Instrum., Vol.75 (6), pp.1988-1996 (2004).

[4] D. F. Ogletree, R.W. Carpick, and M. Salmeron, “Calibration of frictional forces in atomic force microscopy,” Rev. Sci. Instrum., Vol.67 (9), pp.3298-3306 (1996).

[5] R. W. Carpick, “The study of contact, adhesion and friction at the atomic scale by atomic force microscopy,” Ph.D. Thesis, UC Berkeley (1997).