Removal of self-assembled monolayers of alkanethiolates on gold by plasma cleaning

Plasmas of hydrogen or oxygen were used to remove self-assembled monolayers (SAMs) of alkanethiolates from gold surfaces. X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), ellipsometry, and contact angle measurements were used to compare the efficiency of the different plasmas and to explore their respective influence on the surface topology. Both plasmas were able to remove the SAM from the gold surface within less than 60 s. While the hydrogen plasma produces a de facto sulfur-free surface, oxygen plasma cleaning leads to an Au2O3 surface contaminated with oxidized sulfur species (probably sulfonates and sulfate). Nevertheless, the plasmas alter the roughness of the gold surfaces only marginally, as demonstrated by STM.