Preparation And Gas Sensing And Optical Properties Of Doped Nitric Oxide Nanostructures With R (subscript 3) , Er ^{3 +} Doped

SnO₂, an n-type metal oxide semiconductor material, is widely used in the field of gas sensing. Sensor based on the SnO₂ nanostructure has high sensitivity and good selectivity due to its excellent physical and chemical properties. Nowaday, doped SnO₂ materials have been proved effective for improving their sensitivity and selectivity.Pure SnO₂, Y-SnO₂ and Er-SnO₂ nanobelts were prepared by thermal evaporation at 1350 °C with a carrier gas of argon（30 sccm, 112.5 Torr）. These samples were characterized by scanning electron microscope（SEM）, high-resolution transmission electron microscope（HRTEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, and X-ray energy spectrum（EDS）. The sensitivity of three devices based on a single SnO₂ nanobelt, Y-SnO₂ nanobelt, and Er-SnO₂ nanobelt were explored. The results are as follows:（1） The sensitivity of Y-SnO₂ nanobelt device is 11.4 to 100 ppm of acetone at 210 °C, which is the highest sensitivity among acetone, ethanol, and ethanediol gas. This sensitivity is 9.04 times as large as that of pure SnO₂ nanobelt. The sensitivity of 1% Y doped SnO₂ nanobelt device is about 10 to 100 ppm of methane at 190 °C.（2） The responses of 3% and 6% Y doped SnO₂ nanobelt devices are 9.26 and 9 to 100 ppm of methane respectively. More important, the responses of 3% and 6% Y-SnO₂ nanobelt devices are inferior to that of 1% Y-SnO₂ nanobelt device. With the increase of Y³⁺ doping ratio, the response of these devices becomes weaker to 100 ppm of methane at optimum working temperature.（3） In addition, the sensitivity of Er-SnO₂ nanoblet device is explored when it is exposed to formaldehyde, nitrogen dioxide, hydrogen sulfide and carbon oxide. It is found that Er-SnO₂ nanobelt sensor has a high response to 100 ppm of formaldehyde,its sensitivity is 11 and 6.6 times as large as that of pure SnO₂ nanobelt.Its theoretical detection limit to formaldehyde is 141 ppb at optimum working temperature. At the same time, the sensitivities of 3% and 6% Er-SnO₂ nanobelt devices are 9.7 and 9 to 100 ppm of formaldehyde respectively, which are inferior to that of 2% Er-SnO₂ nanobelt.The optical performance of pure SnO₂, Y-SnO₂, Er-SnO₂ nanoblet were measured by Raman, PL, and ultraviolet absorption. It is found that the bandgap of Y-SnO₂, Er-SnO₂ nanoblet are 3.56 e V and 3.48 e V, respectively, which are lower than that of the pure SnO₂ nanobelt（3.67 e V）. The strongest peaks of PL of Y-SnO₂ and Er-SnO₂ nanobelt have shifted towards high frequency（denoted as blue shift） by 3 nm and 2 nm respectively. The reason for the blue shifting is that the radii of Y³⁺ ions（90 pm）, Er³⁺ ions（90 pm） are larger than that of Sn4+ ions（71 pm）, which leads to the change of grain size. Raman spectra peak of Y and Er doped SnO₂ nanobelt also proved a little red shift as compare to that of pure SnO₂ nanobelt.