title: Probing the spatial extension of light trapping-induced enhanced Raman scattering in high-density Si nanowire arrays.
abstract: This paper reports an experimental investigation of surface-enhanced Raman scattering in high-density Si nanowire arrays obtained by electroless etching. A direct relationship between light trapping capabilities of Si nanowires and enhanced Raman scattering was demonstrated. Optimized arrays allowed for a remarkable increase of Raman sensitivity in comparison to reference planar samples. As a result, the detection limit of molecular probes under resonant excitation (e.g. methylene blue) can be extended by three orders of magnitude. In addition, continuous ultrathin films, that cannot be analyzed in conventional Raman experiments, are made detectable. In the case of anatase thin films, the detection limit of 5 nm was reached. Raman spectra of Si/TiO₂ core/shell heterostructures demonstrate that the enhanced field resulting from surface multiple scattering is characterized by a large spatial extension (about fifty nanometers), making these materials a potential alternative to plasmonic metals for SERS experiments.
authors.affiliation: INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze 38, I-25123 Brescia, Italy.
authors.forename: Nicolò
authors.initials: N
authors.lastname: Bontempi
authors.forename: Marco
authors.initials: M
authors.lastname: Salmistraro
authors.forename: Matteo
authors.initials: M
authors.lastname: Ferroni
authors.forename: Laura E
authors.initials: LE
authors.lastname: Depero
authors.forename: Ivano
authors.initials: I
authors.lastname: Alessandri