Large-scale Ag-nanoparticles/Al^sub 2^O^sub 3^/Au-nanograting hybrid nanostructure for surface-enhanced Raman scattering

There has been increasing interest in surface-enhanced Raman scattering (SERS) due to its ability in nondestructive and efficient detection of molecules. However, the fabrication of ideal SERS substrates with large-scale, strong and uniform 'hot spots' was always the challenge for the commercial use of SERS. Here, we designed an Ag-nanoparticles/Al2O3/Au-nanograting hybrid nanostructure as SERS substrate, in which the deep Au nanograting was formed by nanoimprint lithography (NIL) and metal deposition process, and the isolating layer of Al2O3 was deposited by atomic layer deposition (ALD) to form the large area precisely-controlled nanogaps between nanoparticles and nanograting. This hybrid nanostructure utilized the deep metal grating and further the strong local field from multiple coupling systems to realize large-scale and uniform "hot spots". The optimized hybrid structure substrates showed a highly uniform field enhancement, with the enhancement factor of ~5.2 × 107 and the sensitivity of ~10-9 M, which manifested their potential and promising application in commercial use of SERS.