RODRIGUES, E. P.; http://lattes.cnpq.br/3421956160502246; RODRIGUES, Eloise dos Passos.
Abstract:
In this work the development of a sensor system using the surface plasmons resonance phenomenon
in the periodic grating is presented. In order to evaluate the influence of interface
geometry on sensor sensitivity, a theoretical and practical study is performed to calculate the
resonance curve at the periodic interface. The sensor system is designed from the construction
of an optoelectronic device whose characterization in a multilayer structure allows it to be used
to excite the surface plasmons. The device has a sensing region composed of a periodic grating
with sawtooth profile with rounded edges. The analysis of the geometry of this structure
was carried out through a theoretical study, which served as starting point in the mathematical
approach and formulation of the problem. The solution was evaluated from a commercial
computational tool, which uses the finite element method to solve the equations involved considering
all the conditions adopted, whose results were validated through experiments. For the
accomplishment of these experiments, three distinct devices were made, using the metal deposition
process. The metals gold (Au), silver (Ag) and copper (Cu) were deposited in layers
of nanometer scale forming a thin film of metal on the grating. Simulations and experimental
tests were performed on each device built under the same conditions. Two types of studies were
carried out from the incidence of light beam: the first varying the angle of incidence and the second,
the wavelength of light. In both methods, the light had its direct incidence in the metallic
grating aiming to reach a improve the sensitivity of the device. The results obtained by simulations
and experiments, from light reflected by the periodic grating in order zero, were presented
as curve models, whose axes: reflectivity times wavelength and reflectivity times incidence
angle, demonstrated the reflectivity drop for a given wavelength range, or resonance angle. Applications
of the sensor system proposed in this work were glimpsed for the detection of gases,
more specifically condensed water vapor, being analyzed their efficiency and sensitivity in the
detection of this compound.