Comparative study of copper surface treatment with self-assembled monolayers of aliphatic thiol, dithiol and dithiocarboxylic acid

The stability of alkanethiol self-assembled monolayers (SAMs) on metallic substrates, in particular copper, is an important aspect for their application. Some technologies, such as lithographic patterning, can potentially benefit from the use of a transient easily removal protective coatings. Other applications like corrosion resistance, and thin-film lubrication request rather robust and stable films. The aim of this work consists in a comparative investigation of three organothiols (n-tetradecanethiol or RSH, 2-dodecylpropane-1,3-dithiol or R(SH)2 and n-tetradecanedithiocarboxylic or RS2H) on their ability to form SAMs on electrochemically reduced polycrystalline copper substrates and their respective stability. Characterizations of the SAMs are carried out using contact angle goniometry, XPS, PM-IRRAS and electrochemical studies (CV, LSV and cathodic desorption). R(SH)2 leads to monolayers with lower molecular organization than in the case of RSH and RS2H molecules. R(SH)2 monolayers are found the more stable when subjected to both anodic and cathodic desorption tests.