Fabrication of equally oriented pancake shaped gold nanoparticles by SAM-templated OMCVD and their optical response

The optical response of non-spherical gold nanoparticles not only depends on the size of the objects, but also on their shape and orientation with respect to the polarization direction of the light, exciting the plasmon resonance. This study demonstrates a method to grow non-spherical gold nanoparticles via organometallic chemical vapor deposition (OMCVD) onto planar substrates that are covered by SH-terminated self-assembled monolayers (SAMs). Trimethylphosphinegoldmethyl ((CH3)3PAuCH3) is used as the volatile organic precursor. The shape of the deposited particles varies with respect to the nature of the template SAM: disc-like and pancake shaped nanoparticles are fabricated with different aspect rations between the two main axes. UV–vis, AFM, STM, SEM and evanescent waveguide absorption spectroscopy (EWAS) of the OMCVD gold nanoparticles are applied to determine and verify the dimensions and orientation of the nanoparticles in two dimensions. When clusters of nanoparticles are formed, an additional plasmon band with a large red-shift is observed.