Tribological properties of self-assembled monolayers and their substrates under various humid environments
Tribological properties of self-assembled monolayers and their substrates under various humid environments
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DOI：
10.1023/a:1024868532575
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发表时间：
2003-10-01
影响因子：
3.2
通讯作者：
Xiao, XD
中科院分区：
文献类型：
--
作者：
Qian, LM;Tian, F;Xiao, XD
在受控环境下使用摩擦力显微镜（FFM），我们系统地研究了湿度对两类重要的自组装单分子层（SAM）摩擦性能的影响，即SiO2（OTE/SiO2）上的N-十八烷基三甲氧基硅烷（OTE；CH3（CH2）（17）Si（OCH3）（3））； Au(111) 上的 N-烷硫醇以及它们各自的底物。实验结果表明，OTE 和烷基硫醇 SAM 均可降低 Si3N4 原子力显微镜 (AFM) 尖端与基底之间的摩擦力。两种 SAM 的摩擦几乎与湿度无关，表明这些 SAM 是不同环境下微机电系统 (MEMS) 应用的理想润滑剂。 SiO2 和 Au(111) 两种基材的湿度依赖性（随着湿度增加，摩擦力先增加然后减少）可以通过水的吸附来解释。高湿度下摩擦力的降低归因于水多层中的低粘度，而低湿度下摩擦力的增加可以通过水单层和表面（AFM 尖端和样品）之间的高粘度来解释，这可能是由于限制效应。莫迪的影响。还研究了 AFM 尖端与烷硫醇分子的阳离子对 Au(111) 摩擦的湿度依赖性的影响。
Using friction force microscopy (FFM) under controlled environments, we have systematically investigated the humidity effect on the frictional properties of two important classes of self-assembled monolayers (SAMs), i.e., N-octadecyltrimethoxysilane (OTE; CH3(CH2)(17)Si(OCH3)(3)) on SiO2(OTE/SiO2); and N-alkanethiols on Au(111), together with their respective substrates. Experimental results show that both OTE and alkylthiol SAMs can decrease the friction force between a Si3N4 atomic force microscope (AFM) tip and substrates. The nearly humidity-independent friction of the two kinds of SAMs indicates that these SAMs are ideal lubricants in applications of micro-electro-mechanical systems (MEMS) under different environments. The humidity dependence-as the humidity increases, the friction first increases and then decreases-of the two substrates, SiO2 and Au(111), can be explained by the adsorption of water. The decrease in the friction at high humidity is attributed to the low viscosity in the multilayers of water, while the increase in the friction at low humidity can be explained by the high viscosity between the water monolayer and the surfaces (AFM tip and sample), possibly due to the confinement effects. The effect of modi. cation of the AFM tip with alkanethiol molecules on the humidity dependence of Au(111) friction has also been investigated.