Abstract:
We report a novel mechanism to effectively detect LP gas based on
surface modification through sulphidation followed by passivation of
electrodeposited n-type cuprous oxide (Cu2O), forming a thin film n Cu2O/p-CuxS semiconducting heterostructure. Electrochemically
deposited n-type cuprous oxide (n-Cu2O) thin films on Ti substrates
in acetate bath were sulphided using Na2S to fabricate n-Cu2O/p CuxS heterostructures. Subsequent passivation of these thin film
structures using (NH4)2S vapor enhanced the sensitivity (fractional
change in thin film resistance) when exposed to liquefied petroleum
(LP) gas.
Scanning electron micrographs (SEM) confirmed that typical
unsulphided n-type Cu2O thin films exhibit polycrystalline surface
morphology, while SEM of both sulphided and passivated thin films
revealed micro/nano-crystalline surface morphological features with
porous structures. As expected, the thin film structures obtained
through sulphidation followed by passivation of n-type Cu2O films
decreased the resistance (100 kΩ) in comparison to the resistance
(1 MΩ) of the unsulphided n-type Cu2O thin films. Upon exposure
to LP gas, the resistance of these thin film structures increased
while, sensitivity to LP gas depended on the sensing temperature.
Exposure of thin film structures fabricated by electrodepositing n-type Cu2O thin films for 45 min, sulphided and passivated for 5 s
and maintained at a sensing temperature of 45 ºC to LP gas with a
flow rate of 2.5 ml/min recorded the highest sensitivity of 48 %.
