posted on 2020-03-19, 18:51authored byLuca Francioso, Chiara De Pascali, Pasquale Creti, Antonio V. Radogna, Simonetta Capone, Antonietta Taurino, Mauro Epifani, Chiara Baldacchini, Anna R. Bizzarri, Pietro A. Siciliano
In
this work, an experiment was carried out in order to exploit
the physical properties of an electrode structure with nanometric
gap to enable the operation of MOX sensors at low temperature independently
from the gas sensing properties of the adopted active material. The
100 nm-gap fingers gas sensor array was fabricated by using electron
beam and UV optical lithography onto 4″ silicon wafers (guaranteeing
high process yield). SnO2 nanoparticles (NPs) synthesized
by sol–gel/solvothermal method were trapped between the nanogap
electrodes by dielectrophoresis, and scanning electron microscopy
and atomic force microscopy surface analysis were used to investigate
the semiconducting NPs dispersion between the nanogap fingers. Nanogap
SnO2 NPs based-sensor responses to acetone and ethanol
in dry air carrier gas at near room temperatures were reported, discussed,
and compared with those obtained from 5 μm gap gas sensors (comparable
to standard microgap commonly used in commercial sensors) functionalized
with the same sensing material. The nanogap sensors exhibited better
performance compared to the microgap ones, and larger response to
ethanol than to acetone. For the lowest investigated gas concentration
(10 ppm), the ethanol response (Rair/Rgas) increased with temperature from 2.56 at
50 °C to 17.91 to 100 °C, respectively from 1.56 to 3.92
for acetone. The best nanogap sensor responses were found at 100 °C
with Rair/Rgas ≈ 38 for 150 ppm of ethanol, and Rair/Rgas ≈ 10 for 150 ppm of acetone.
The experimental measurements confirmed the adopted theoretical model
correlation between the sensor responses and the electrodes separation
gap.