We investigated optical properties of planar Si wafers and Si microwire (MW) arrays with and without ZnO thin films using the finite-difference time-domain (FDTD) method. Reflectance of the MW array (diameter: 4 μm and period: 12 μm) was smaller than that of the planar wafer in the wavelength range from 400 to 1100 nm, which could be originated from antireflection effects due to low optical density and guided-mode-assisted field enhancement. The reflectance of ZnO (thickness: 50 and 80 nm)-coated MW array was drastically reduced compared with the bare array but somewhat larger than that of the coated planar wafer. This could be attributed to less-confined guided modes in the wires, which was supported by the field distribution simulation results. Our results provide some insights into possible roles of transparent conducting layers on MW arrays for photovoltaic applications.
We have investigated optical characteristics of silicon nanowire (Si NW) on Al disk arrays using the finite-difference
time-domain (FDTD) simulations. Without the Al disk, the Si NW arrays alone exhibit strong absorption peaks,
originated from guided mode resonance. The arrays of SiNW with Al disk possess additional broad peaks, at slightly
larger wavelengths than those of the resonant guided mode peaks. The FDTD simulations show formation of
concentrated electromagnetic field at the Si NW/Al interface, indicating excitation of localized surface plasmons. These
results suggest that bottom-contact electrodes can work as means to enhance the optical absorption of the Si NWs as well
as to collect carriers in Si NW-based optoelectronic devices.
We investigated the optical properties of ZnO/Ag grating structures, with the periods of 1000 and 1400 nm, fabricated by
sputtering and nanoimprint lithography. The grating structures exhibited multiple peak features in visible-range
photoluminescence (PL) spectra. Whereas a ZnO/Ag planar thin film showed two broad PL peaks in UV and visible
region. Moreover, the PL intensity of the periodic structures was ~100 times larger than that of the planar counterpart.
Several reflectance dips in the visible range were seen only in the grating structures, which could be caused by photoninduced
surface plasmon polariton (SPP) excitation via the grating coupling. The PL peaks well matched with the
reflectance dips. This represented that the PL enhancement should be originated from the SPP excitation. The finitedifference
time-domain simulations also supported the plasmonic effects in the periodic structures.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.