An atom probe analysis of self-assembled monolayers: A novel approach to investigate mixed and unmixed self-assembled monolayers (SAMs) on gold

• Published in: Applied surface science 2019-11, Vol.494, p.152-161
• Main Authors: Mohanty, Sandeep Kumar, Tolochko, Oleg
• Format: Article
• Language: English
• Subjects: Atom probe tomography; Mixed and unmixed SAMs; Monolayer structure; Phase transition; Self-assembled monolayer; Thiols
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.07.011

Atom probe tomography was used to analyze self-assembled monolayer of octanethiol and (1H,1H,2H,2H) perfluoro decanethiol (PFDT) in a mixed and unmixed state on a gold surface. The first part of this report, we have analyzed the two SAMs with a direct comparison, whereas in the second part, a binary mixture of these two SAMs (with a 1:1 ratio) are analyzed. Au was taken as a metal substrate in both cases. It has been observed that, although having similar structure and belongs from the same SAMs group, the sequence of evaporation of both chains appeared significantly different molecular fractions in the first case, while in the mixed phase condition the two SAMs chains were arranged in a patchy domain by forming a small nanoscale cluster on the gold surface. Primarily, this study gives an overall understanding of evaporation sequence and surface morphology of the SAMs in an unmixed and mixed condition on the gold substrate, which may lead to the further design process in various applications. •Two types of Self assembled monolayer named octane thiol and (1H,1H,2H,2H) perfluoro decanethiol (PFDT) has been taken for the study.•The overall analysis is mainly done by Laser assisted Atom probe tomography (APT) machine.•Both the SAMs investigated individually as well as in a mixed condition by APT machine.•A difference in sequence of evaporation has been noticed between two chain in a separate phase condition.•While in the mixed phase condition the two SAMs chains were arranged in a patchy domain on the gold surface.•Primarily, this study gives an overall understanding of evaporation sequence and surface morphology of the SAMs in an unmixed and mixed condition.