Ultrahigh-Sensitive Tin-Oxide Microsensors for H<tex>$_2$</tex>S Detection

Room-temperature H2S gas sensing at ppb level by single crystal In2O3 whiskers

“…Semiconductor gas sensors have proved to be a low cost and convenient option for monitoring of gas species and sensors in the form of thin or thick films, based on metal oxides like SnO 2 , WO 3 and p-n heterojunctions (SnO 2 -CuO), have been reported for detection of H 2 S gas [4][5][6][7][8] in a ppm range. Recently such sensors for low concentrations have also been reported [9][10][11][12]. Efforts are also being made to use nano-crystalline materials for room-temperature detection of H 2 S. Ionescu et al [9] reported WO 3 nano-particle films (operating temperature of 150-250 • C) and Esfandyarpour et al [10] reported spin coated nano-crystalline SnO 2 :CuO films to sense low concentrations of H 2 S at 85-170 • C. Nano-crystalline ZnO sensors were found to have very slow recovery (∼1 h) at 85 • C but satisfactory response and recovery times at 170 • C. However, nano-materials are inherently more reactive and hence susceptible to morphological and property changes during post growth processing and also during operation.…”

“…Recently such sensors for low concentrations have also been reported [9][10][11][12]. Efforts are also being made to use nano-crystalline materials for room-temperature detection of H 2 S. Ionescu et al [9] reported WO 3 nano-particle films (operating temperature of 150-250 • C) and Esfandyarpour et al [10] reported spin coated nano-crystalline SnO 2 :CuO films to sense low concentrations of H 2 S at 85-170 • C. Nano-crystalline ZnO sensors were found to have very slow recovery (∼1 h) at 85 • C but satisfactory response and recovery times at 170 • C. However, nano-materials are inherently more reactive and hence susceptible to morphological and property changes during post growth processing and also during operation. In 2 O 3 is known to be an n-type semiconductor in its nonstoichiometric form, due to oxygen vacancy doping [13] and has been extensively studied as a conductivity-based chemical sensor.…”

Characterization of CuO phase in SnO2–CuO prepared by the modified Pechini method

“…This behavior has been attributed to the formation of p-n heterojunctions (p-CuO and n-SnO 2 ), which induces an electron depleted space charge layer at the surface of SnO 2 [3,6,9]. Upon exposure to H 2 S, the p-type semi-conducting CuO particles are converted to CuS having metallic properties [10]. This transformation destroys the p-n junctions and results in a large drop in electrical resistance.…”

A Low-Cost Intelligent Gas Sensing Device for Military Applications

“…The sensors chosen for this application are tin oxide sensors ( 2 SnO ) [4]. The sensors have two pins for the heater circuit and two or four pins for the sense resistor.…”