Enhanced Optical Absorption and Spectral Photocurrent in a-Si:H by Single- and Double-Layer Silver Plasmonic Interfaces

Single and double plasmonic interfaces consisting
of silver nanoparticles embedded in media with different
dielectric constants including SiO 2 , SiN x , and Al:ZnO have
been fabricated by a self-assembled dewetting technique and
integrated to amorphous silicon films. Single plasmonic inter-
faces exhibit plasmonic resonances whose frequency is red-
shifted with increasing particle size and with the thickness of a
dielectric spacer layer. Double plasmonic interfaces consisting
of two different particle sizes exhibit resonances consisting of
double minima in the transmittance spectra. The optical ex-
tinction of a-Si:H deposited on these interfaces is broadened
into the red indicating higher absorption and/or scattering at
wavelengths higher than those typically absorbed by a-Si:H
without plasmonic interfaces. While the photocurrent shows
an overall decrease for the samples with the interfaces, signif-
icant enhancement of photocurrent is observed near the low-
energy edge of the bandgap (600 – 700 nm). These results
correlate well with the broadened extinction spectra of the
interfaces and are interpreted in terms of enhanced absorption
in that region.