Light absorption enhancement in thin silicon film by embedded metallic nanoshells

Computer simulation studies of absorption enhancement in a silicon (Si) substrate by nanoshell-related localized surface plasmon resonance (LSPR) based on a finite-difference time-domain analysis are presented. The results of these studies show significant enhancement of over 15x in the near-bandgap spectral region of Si, using 40 nm diameter, two-dimensional silver (Ag) nanoshells, simulating cylindrical nanoshell structure. The studies also indicate a clear advantage of the cylindrical nanoshell structure over that of a completely filled Ag-nanocylinders. The enhancement was studied as a function of the metallic shell thickness. The results suggest that the main enhancement mechanism in this case of tubular nanoshells embedded in the Si substrate is that of field-enhanced absorption caused by the strong LSPR-enhanced electric field, extending into the silicon substrate.