High Gas Sensitivity to Nitrogen Dioxide of Nanocomposite ZnO-SnO(2) Films Activated by a Surface Electric Field

Gas sensors based on the multi-sensor platform MSP 632, with thin nanocomposite films based on tin dioxide with a low content of zinc oxide (0.5–5 mol.%), were synthesized using a solid-phase low-temperature pyrolysis technique. The resulting gas-sensitive ZnO-SnO(2) films were comprehensively studied by atomic force microscopy, Kelvin probe force microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. The obtained films are up to 200 nm thick and consist of ZnO-SnO(2) nanocomposites, with ZnO and SnO(2) crystallite sizes of 4–30 nm. Measurements of ZnO-SnO(2) films containing 0.5 mol.% ZnO showed the existence of large values of surface potential, up to 1800 mV, leading to the formation of a strong surface electric field with a strength of up to 2 × 10(7) V/cm. The presence of a strong surface electric field leads to the best gas-sensitive properties: the sensor’s responsivity is between two and nine times higher than that of sensors based on ZnO-SnO(2) films of other compositions. A study of characteristics sensitive to NO(2) (0.1–50 ppm) showed that gas sensors based on the ZnO-SnO(2) film demonstrated a high sensitivity to NO(2) with a concentration of 0.1 ppm at an operating temperature of 200 °C.