Formation of self-assembled monolayers of n-alkanethiols on gold: a scanning tunneling microscopy study on the modification of substrate morphology

Single-crystal Au(lll) surfaces covered with self-assembled monolayers of n-alkanethiols (CH3(CH2)n-iSH) (n = 6, 22) are investigated with scanning tunneling microscopy. After adsorption new morphological features are observed which can be shown to originate from a removal of 30-50% of a monolayer of Au atoms from the surface into the solution. Only a very low concentration of defects within the films (“pinholes”) was observed. In addition experimental evidence for two different tunneling mechanisms in short and long alkyl chains is provided.