CC BY
17LD-I-12
Plasmon-enhanced optical spectroscopies of semiconductor nanostructures
A. Milekhin1, M. Rahaman2, T. Duda1, E. Rodyakina3, R. Vasiliev4, K. Anikin1, V. Dzhagan5, A. Latyshev3, D. Zahn2
1A.V. Rzhanov Institute of Semiconductor Physics, Laboratory of near-field optical spectroscopy and nanosensorics, Novosibirsk, Russian Federation
2Chemnitz University of Technology, Semiconductor Physics, Chemnitz, Germany 3A.V. Rzhanov Institute of Semiconductor Physics, Laboratory of Nanodiagnostics and Nanolithography, Novosibirsk, Russian Federation
Moscow State University, Department of Material Science, Moscow, Russian Federation 5V.E. Lashkaryov Institute of Semiconductor Physics, Department of Optics and Spectroscopy of Semiconductor and Dielectric Materials, Kiev, Ukraine
The results of a Tip-Enhanced Raman Scattering (TERS) and Surface-Enhanced InfraRed Absorption (SEIRA) study of CdSe nanocrystals (NCs) and CdSe/CdS nanoplatelets (NPLs) on arrays of Au nanodiscs and nanoantennas fabricated using nanolithography are discussed. Monolayers (MLs) of CdSe NCs with a size of 5-6 nm and sub-MLs of CdSe/CdSe NPLs consisting of 1.5 nm CdSe core and 0.6 nm CdS shell were deposited on plasmonic substrates using the Langmuir-Blodgett technology.
TERS by longitudinal optical (LO) and surface optical (SO) phonons in CdSe-based nanostructures placed in the gap between the TERS tip apex and Au nanodiscs was observed. The spatial variation of LO and SO frequencies is explained by the heating induced by the strong local field under localized surface plasmon resonance (LSPR) conditions.
The TERS signal from CdSe NCs on Au nanodisk arrays forms a pattern of ordered rings with a diameter equal or below that of the Au nanodisks dependent on the excitation energy. A superposition of the TERS image on the corresponding AFM topography shows that the centers of the rings and Au nanodisks perfectly coincide. This indicates that the TERS signal strongly depends on the LSPR energy of the coupled system of the tip and the nanodisk and their relative position.
TERS maps for CdSe/CdS NPLs reproducing the size and shape of the NPLs are consistent with AFM images and allowed the phonon spectrum of single NCs and NPLs to be investigated. SEIRA by optical phonons of MLs of CdSe-based nanostructures on Au nanoantennas with structural parameters allowing the coupling of the LSPR and diffraction modes is discussed. The frequency positions of the absorption features evidence that the SO phonons of the NCs are active in the SEIRA spectra.
Acknowledgements
The reported study was funded by Volkswagen Foundation and RFBR in the research projects 19-52-12041 and 18-02-00615.
