H 2 S gas sensing mechanism of SnO2 films with ultrathin CuO dotted islands

Abstract

H 2 S gas interaction mechanisms of sputtered SnO2 and SnO2–CuO bilayer sensors with a varying distribution of the Cu catalyst on SnO2 are studied using Pt interdigital electrodes within the sensing film. Sensitivity to H2S gas is investigated in the range 20–1200 ppm. Changes induced on the surface, the SnO2–CuO interface, and the internal bulk region of the sensing SnO2 film upon exposure to H2S have been analyzed to explain the increasing sensitivity of three different sensors SnO2, SnO2–CuO, and SnO2 with CuO islands. SnO2 film covered with 0.6 mm diameter ultrathin (∼10 nm) CuO dots is found to exhibit a high sensitivity of 7.3×103 at a low operating temperature of 150 °C. A response speed of 14 s for 20 ppm of H2S, and a fast recovery time of 118 s in flowing air have been measured. The presence of ultrathin CuO dotted islands allow effective removal of adsorbed oxygen from the uncovered SnO2 surface due to spillover of hydrogen dissociated from the H2S–CuO interaction, and the spillover mechanism is sensed through the observed fast response characteristics, and the high sensitivity of the SnO2–CuO-dot sensor.

Synthesis and Humidity Sensing Investigations of Nanostructured ZnSnO<sub>3</sub>

“…The mechanisms of the electrical response of semiconducting materials to humidity was explained taking consideration of the chemically and physically adsorbed layers of water molecules as well as capillary condensation of water inside tiny pores [41]. The porous microstructure and the surface reactivity with water are key parameters for the performance of semiconducting humidity materials [42].…”

Mechanism Of Trace Level H2S Gas Sensing Using Rf Sputtered SnO2 Thin Films With Cuo Catalytic Overlayer

“…In view of this problem, a sputtering pressure of 14 mTorr and a reactive gas ambient of Ar : O 2 = 50 : 50 was considered to be optimum conditions for depositing SnO 2 films for gas sensor applications. catalyst with SnO 2 sensing layer [1]. Table 2.…”

“…[1] are known to exhibit enhanced sensitivity, better selectivity and fast response speeds to various reducing gases including H 2 S. SnO 2 sensor is invariably anion deficient and oxygen vacancies are mainly responsible for making available free electrons for the conduction process [2]. In addition, the surface morphology of the sensing layer is also important for realization of sensor with enhanced response characteristics, which in turn depend on the growth kinetics.…”

“…[4] reported highly sensitive H 2 S gas sensors operating at relatively low temperatures with CuO as the catalyst material. Some of the extensively investigated sensor structures for H 2 S gas detection include, mixed SnO 2 -CuO powders [5], CuSnO 2 bi-layers [6], CuO-SnO 2 hetero-structures besides others [1,7]. Processing conditions have been noted to have a significant influence on the sensing response characteristics.…”

OPTICAL AND PHOTOLUMINESCENT STUDIES ON VO2+ DOPED SnO2 THIN FILMS

“…Among all the transition metal ions, tin oxide (SnO2) is a promising candidate in the field of catalysis, photograph, electronics, photonics, data storage, optoelectronics etc. Moreover tin oxide thin films have many merits, such as non toxic, wide band gap(3.4-3.6 eV), excellent optical transparency with n-type semiconducting nature 12 .The main drawback of SnO2 thin films is to control oxygen at deposition process, due to non-stoichiometric nature of oxygen; SnO2 converts the metastable phases as SnO or Sn3O4 and conduction phenomenon takes place in SnO2 thin films due to random distribution of electrons 13,14 . Vanadium (V) is a natural abundance element which is freely available from earth crust.…”