31 research outputs found
Plasmonic modes of gold nano-particle arrays on thin gold films
Regular arrays of metal nanoparticles on metal films have tuneable optical
resonances that can be applied for surface enhanced Raman scattering or
biosensing. With the aim of developing more surface selective geometries we
investigate regular gold nanoparticle arrays on 25nm thick gold films, which
allow to excite asymmetric surface plasmon modes featuring a much better field
confinement compared to the symmetric modes used in conventional surface
plasmon resonance setups. By optical extinction spectroscopy we identify the
plasmonic modes sustained by our structures. Furthermore, the role of thermal
treatment of the metal structures is investigated, revealing the role of
modifications in the crystalline structure of gold on the optical properties.Comment: 8 pages, 3 figure
Raman study of Fano interference in p-type doped silicon
As the silicon industry continues to push the limits of device dimensions,
tools such as Raman spectroscopy are ideal to analyze and characterize the
doped silicon channels. The effect of inter-valence band transitions on the
zone center optical phonon in heavily p-type doped silicon is studied by Raman
spectroscopy for a wide range of excitation wavelengths extending from the red
(632.8 nm) into the ultra-violet (325 nm). The asymmetry in the one-phonon
Raman lineshape is attributed to a Fano interference involving the overlap of a
continuum of electronic excitations with a discrete phonon state. We identify a
transition above and below the one-dimensional critical point (E = 3.4 eV) in
the electronic excitation spectrum of silicon. The relationship between the
anisotropic silicon band structure and the penetration depth is discussed in
the context of possible device applications.Comment: 6 pages, 7 figures, pape