Vibrational sum frequency spectroscopy of thin film interfaces

We describe a basic theoretical treatment of how film-substrate and substrate-environment (air, water, and solution) interfaces can be selectively probed by controlling the film thickness and beam angles in a visible-infrared sum frequency generation experiment. In this model, we also account for the unique interfacial environment that may have optical properties that differ from the adjacent bulk phases. We see that this affects components of the electric field that are perpendicular to the surface such as when p-polarized light is used. We then provide an example using the glass-polydimethylsiloxane-air system and model the fields at both surfaces of the polymer. This is followed by some practical considerations for setting up such experiments and some typical experimental results.

Automated summary

We present a basic theoretical treatment of selectively probing film-substrate and substrate-environment interfaces in a visible-infrared sum frequency generation experiment by controlling film thickness and beam angles. We also account for the unique optical properties of the interfacial environment. Using the glass-polydimethylsiloxane-air system as an example, we model the electric fields at both surfaces of the polymer. We also provide practical considerations for setting up such experiments and present typical experimental results.