Raman Scattering for Probing Semiconductor Nanocrystal Arrays with a Low Areal Density

We present a study of resonant and surface enhanced Raman scattering by arrays of nanocrystals (cadmium sulfide CdS, lead selenide PbSe, and zinc oxide ZnO) with various areal density fabricated by using the Langmuir–Blodgett technique and colloidal chemistry. Resonant Raman scattering by transverse, longitudinal, and surface optical (TO, LO, and SO) phonons and their overtones up to ninth order was achieved for nanocrystal (NC) arrays by adjusting the laser energy to that of the interband transitions. The resonance enhancement allowed a Raman response from arrays of NCs with a low areal density (down to 10 PbSe NCs per 1 μm²) to be measured. An enhancement of Raman scattering by LO and SO modes in CdS NC arrays with a low areal density by a factor of about 730 was achieved due to the resonant surface enhanced Raman scattering effect