Detection of Low-Density Ge Nanoparticles Using Surface-Enhanced Raman Spectroscopy

摘要

We demonstrate the sensitive detection and structural characterization of extremely low density Ge nanoparticles by surface-enhanced Raman spectroscopy (SERS). Ge films of monolayer coverage are fabricated by a gas evaporation technique and are deposited onto quartz and various metal substrates. The nanoparticle size and density, as obtained by transmission electron microscopy, are in the range of 6-9 nm and ～1.2×10~11 cm~(-2) respectively. The Raman intensity for the Ge films deposited on metal substrates (Ag, Au, or Al) shows a dramatic enhancement (for example, a factor of a few hundred for Ag) as compared to quartz substrates. Further, the Raman intensity enhancement from the different metals is understood in terms of contributions from interband transitions to the dielectric function in the visible excitation region used for Raman measurements. The observation of enhanced Raman signals from such low-density NP films shows the potential of non-invasive Raman spectroscopy for the study of optical and structural properties of nanoscale devices.