Self-Assembly Process in Stronger Molecule-Substrate Interaction: Alkanethiols on Si (111)
Lo Yueh Chang1,2*, Hung Wei Shiu1, Chih Yi Chen1, Shangjr Gwo1,2, Chia-Hao Chen1
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
* presenting author:張羅嶽,
Highly ordered organic molecules have attracted a lot of attention because the electronic characteristics are improved by reduction of defects and domain boundaries. Spontaneously ordered structure of organic molecule on substrate surface takes place by the intermolecular Van der Waals’ force and weaker molecule-substrate interaction, called self-assembly process. The simplest system is self-assembled monolayer (SAM), having well-ordered and two-dimensional monolayer, controllable tail group, and varied substrate for understanding the role of self-assembly process. However, in the stronger molecule-substrate interaction, it is seldom discussed the growth mechanism and resulting monolayer.
In this work, we report the alkanethiols (ATs, SH(CH2 )n CH3 , n = 4 ~ 16) on Si (111) surface to understand the molecular and ordered structure formed by stronger S-Si bond. The resulting monolayer is determined by means of water contact angle measurement and synchrotron based and high-resolution X-ray photoelectron spectroscopy (HR-XPS) to verify the chemical states. Then, molecular structures of AT/Si(111) are monitored by near-edge X-ray absorption fine structure spectroscopy (NEXAFS) to analyze molecular orientations. By combing those surface analysis measurements, the growth behaviors are understood in the role of molecule-substrate interaction.

Keywords: Self-assembled Monolayer