Sum Frequency Generation Imaging Microscopy of Self-Assembled Monolayers on Metal Surfaces: Factor Analysis of Mixed Monolayers.

Sum frequency generation (SFG) images of microcontact patterned self-assembled alkanethiol monolayers on metal surfaces were analyzed by factor analysis (FA) to determine the spatial distribution of the patterned monolayers over the images. Additionally, each significant abstract factor produced by FA was assessed to determine the information contained within it. These results indicate that FA of the SFG spectra is a promising method to determine the composition and identities of mixed alkanethiol systems that show different vibrational spectra and image contrast. Factor analysis has successfully been applied to SFG images obtained with low signals, which reduces the time required for full spectral SFG imaging.