Self-assembled monolayers (SAMs) of molecules have been reported to show improved structural quality when formed at elevated temperatures, but this effect has long been somewhat ignored in the field of molecular electronics. In this study, electrical measurements such as current-voltage characteristics were combined with scanning tunneling microscopy images to analyze the correlation between the SAM formation temperature and the resulting electrical properties of SAM junctions, using alkanethiol. Increasing the formation temperatures enhanced the conductance of SAM junctions, which is associated with the improved structural quality of SAMs with fewer defects and larger domains. Additionally, rectifying behavior was found to be related to the conductance of SAMs. A close examination of the current-voltage characteristics revealed that the rectification is due to an asymmetrical shift of highest occupied molecular orbital under bias. Defects in SAMs account for the rectification as well as its correlation with the conductance. Based on these observations, it was found that the formation temperature affects the electronic properties of SAM junctions by controlling defects. This study elucidates the causal relationship between the SAM formation process and the resulting electrical properties of SAM junctions.

 

Authors: Hyemin Lee, Haeri Kim, Donguk Kim, Jongwoo Nam, Minwoo Song, Hyun Sun Sung, Jaegeun Noh*, and Takhee Lee* (*co-corresponding authors)

 

DOI: https://doi.org/10.1021/acsnano.5c07611

Published online: October 4, 2025

Link: https://pubs.acs.org/doi/full/10.1021/acsnano.5c07611