SERS Spectroscopy For Studying The Interface Between Self-Assembled Semiconductor Quantum Dots And Biomolecules.

Motivated by the sensitivity of surface enhanced Raman spectroscopy (SERS) to very small amounts of material and by our illustration of an enhanced Raman sensitivity of molecules adsorbed on self-assembled semiconductor quantum dots (1, 2), we explore the application of the SERS technique for directly probing the interface between semiconductor quantum-dots and biological molecules. The objective is the development of SERS spectroscopy as a fundamentally new method for studying biologically inspired systems in which nanostructured materials, especially semiconductors, play an important role. This will provide new and fundamental insights into the role of interfaces. SERS spectroscopy is a very sensitive technique that employs rough substrates with structures on the scale of nanometers to enhance the Raman signal produced by adsorbed species. We have observed the SERS spectra of tyrosine molecules adsorbed on self-assembled InAs/GaAs quantum dots, grown by molecular beam epitaxy. These spectra provide detailed molecular information on chemical composition, molecular structure, orientation on the surface, and order. This demonstrates that SERS can be used to directly probe the adsorption of molecules on MBE-grown semiconductor quantum-dots. This work shows that SERS has extremely high sensitivity to identify adsorbed species and provide insight into the nature of interaction of adsorbate with substrate. Thus, the SERS technique can provide a useful and versatile technique to probe interfacial structures.