Self-assembled monolayers of cyanoterphenyl terminated alkyl disulfides studied by vibrationally and electronically doubly-resonant sum-frequency generation spectroscopy

► SAMs of cyanoterphenyl terminated alkyl disulfides were studied by DR-SFG. ► Intense bands of the terphenyl were observed due to electronic resonance. ► Number density of the terphenyl on LC-monomer SAM was 1/2 of what it was on LC-dimer. ► DR-SFG signal of the former was larger than those of the latter. ► The findings were explained by the difference of the orientation distributions.