High Gas Sensitivity to Nitrogen Dioxide of Nanocomposite ZnO-SnO2 Films Activated by a Surface Electric Field
Victor Petrov, Alexandra P. Ivanishcheva, Maria G. Volkova, Viktoriya Yu. Storozhenko, Irina A. Gulyaeva, Ilya Pankov, В. А. Волочаев, Soslan A. Khubezhov, Е. М. Bayan
Abstract
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-SnO2 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-SnO2 nanocomposites, with ZnO and SnO2 crystallite sizes of 4–30 nm. Measurements of ZnO-SnO2 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 × 107 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-SnO2 films of other compositions. A study of characteristics sensitive to NO2 (0.1–50 ppm) showed that gas sensors based on the ZnO-SnO2 film demonstrated a high sensitivity to NO2 with a concentration of 0.1 ppm at an operating temperature of 200 °C.