Abstract:
The surface of electrodeposited n-Cu2O thin films were modified by sulphidation using aqueous
Na2S followed by (NH4)2S vapor treatment. Compared to untreated thin films, the resultant
films showed an enhanced response to liquefied petroleum (LP) gas at a relatively low operating
temperature (~45 °C), one of the lowest reported for a cuprous oxide based material. X-ray
diffraction spectra confirmed that the films were of single phase. Observed by contact angle
measurements and energy dispersive x-ray spectroscopy, (NH4)2S vapor treatment converted
the highly wetting sulphided films containing both Na and S to a partially wetting surface by
forming sulphur on the film surface. This modification on the film surface, enabled the sensor
response to recover to an ambient level after stoppage of LP gas flow, which sulphidation alone
was inapt. Scanning electron micrographs complemented roughness measurements made by
atomic force microscopy and showed a transformation of polycrystalline morphology of bare
n-Cu2O film to one having highly porous structures, which thereby increased the surface area of
the surface modified films. Therefore, this work demonstrates that the surface of the n-type Cu2O
thin films modified by (NH4)2S vapor treatment and sulphidation can alter the surface wetting
nature and increase the surface area to enhance LP gas sensing at a relatively low temperature.
