A New Single-Molecule Detection: the Gain-Assisted Surface Enhanced Raman Scattering via Nanostructured Ingan Quantum Wells

This project is to map out a new route for single molecule detection. We propose a III-nitride nanostructure as the next-generation platform for surface enhanced Raman scattering (SERS), with which the SERS intensity will be greatly boosted via a gain medium. The platform employs a metal/nano-quantum-well composite as the surface structure to form the so-called“hot spots”, i.e. the regions with significantly enhanced SERS intensities. The nanostructured quantum wells are made of InGaN and grown by metal-organic chemical vapor deposition (MOCVD), whose operation parameters can uniformly control geometric dimension and distribution density of the hot spots. Compared with the commonly used nanoparticle aggregates on flat surface, hot spots created by the MOCVD method are of much higher controllability, and are expected to improve the detection sensitivity. The InGaN quantum wells (QWs) act as the gain medium, pumping energy to the surface plasmons created at the metal/semiconductor interface. Consequently, the QW properties (including emission wavelength, emission intensity, surface roughness, etc.) are closely related to the density and the intensity of the hot spots. GaN and its compounds are chemically inert, physically robust, and biocompatible, making the compound an ideal substrate for single molecule detection. The proposed SERS structure is not only expecting much enhanced detection sensitivity, but also shows promising potentials in industrial applications. We aim to provide keys to the conundrums faced by single-molecule-detection studies over the years.