In situ Structural Characterization of Metal−Molecule−Silicon Junctions Using Backside Infrared Spectroscopy

In-situ infrared spectroscopy of metallized aromatic molecular monolayers directly bound to silicon has been performed. Monolayers of two nitro-containing species were characterized before metallization using transmission mode and following metallization using a p-polarized backside reflection technique. The vibrational signature of the molecular layer is not significantly altered after vapor-depositing gold using a soft evaporation technique; however, standard gold evaporation completely destroys the molecular signature. The time evolution of vibrational peaks associated with the molecular layer and surface silicon oxide species shows that the molecular layer is stable, but the silicon oxide evolves over time within the junction.