Ald grown zno as an alternative material for plasmonic and uncooled infrared imaging applications
Author
Kesim, Yunus Emre
Advisor
Okyay, Ali Kemal
Date
2014Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Plasmonics is touted as a milestone in optoelectronics as this technology can form
a bridge between electronics and photonics, enabling the integration of electronics
and photonic circuits at the nanoscale. Noble metals such as gold and silver have
been extensively used for plasmonic applications due to their ability to support
plasmons, yet they suffer from high intrinsic optical losses. Recently, there is
an increased effort in the search for alternative plasmonic materials including Si,
Ge, III-Nitrides and transparent conductive oxides. The main appeal of these
materials, most of them semiconductors, is their lower optical losses, especially in
the infrared (IR) regime, compared to noble metals owing to their lower number of
free electrons. Other advantages can be listed as low-cost and control on plasma
frequency thanks to the tunable electron concentration, i.e. effective doping level.
This work focuses on atomic layer deposition (ALD) grown ZnO as a candidate
material for plasmonic applications. Optical constants of ZnO are investigated
along with figures of merit pertaining to plasmonic waveguides. It is shown that
ZnO can alleviate the trade-off between propagation length and mode confinement
width owing to tunable dielectric properties. In order to demonstrate plasmonic
resonances, a grating structure is simulated using finite-difference-time-domain
(FDTD) method and an ultra-wide-band (4-15 µm) infrared absorber is computationally
demonstrated.
Finally, an all ZnO microbolometer is proposed, where ALD grown ZnO is employed
as both the thermistor and the absorber of the microbolometer which is an
uncooled infrared imaging unit that relies on the resistance change of the active
material (thermistor) as it heats up due to the absorption of incident electromagnetic
radiation. The material complexity and process steps of microbolometers
could be reduced if the thermistor layer and the absorber layer were consolidated
in a single layer. Computational analysis of a basic microbolometer structure
using FDTD method is conducted in order to calculate the absorptivity in the
long-wave infrared (LWIR) region (8-12 µm). In addition, thermal simulations
of the microbolometer structure are conducted using finite element method, and
time constant and noise-equivalent-temperature-difference (NETD) values are extracted.
Keywords
PlasmonicsAlternative Plasmonic Materials
Transparent Conductive Oxides
Metal Oxides
ZnO
Atomic Layer Deposition
FDTD Method
Uncooled İnfrared İmaging
Microbolometer
All-ZnO Microbolometer