Author: Dietrich R.T. Zahn
Requested Type: Oral
Submitted: 2015-03-30 13:50:28
Co-authors: A. Milekhin, V. Dzhagan
Technische Universität Chemnitz
Quantum dots (QDs) of semiconductors such as CdSe with and without shells of wider bandgap material have intriguing properties, e.g. the effective bandgap which varies from the red spectral region to the blue one as the QD size decreases. Raman spectroscopy is employed to study the vibrational spectra of such QDs. With decreasing size surface optical phonon contributions and a shoulder at the high frequency side of the bulk-like LO phonon contribution become prominent, especially for ultra-small QDs with diameters of less than 2 nm. QDs with a shell are prone to intermixing and strain effects at the interface to the core. Multi-phonon scattering allows the electron-phonon coupling in QDs to be estimated. Typically Raman spectra are taken of an ensemble of many QDs. Recent advances in detecting the response of very few QDs are presented. In this case several means of enhancing the Raman signals of QDs are employed including interference enhancement and surface enhancement by ordered arrays of metal nanostructures. When using single dimers of metallic nanostructures the Raman spectra of single QDs in the hot spot between the dimers can be recorded.