Rheotaxially Grown and Vacuum Oxidized SnOx Nanolayers for NO2 Sensing Characteristics at ppb Level and Room Temperature

Abstract

This work presents, for the very first time, very promising nitrogen dioxide (NO 2 ) sensing characteristics of SnO x nanolayers obtained by the innovative and unique rheotaxial growth and vacuum oxidation (RGVO) processing technique. The NO 2 gas sensing experiments were performed using the novel surface photovoltage gas sensing device. The measured detection limit at room temperature (RT) is as low as 10 ppb NO 2 in synthetic air, whereas the detection limit calculated on the basis of signal to noise ratio is around 6 ppb NO 2 . For the complementary study of surface chemistry of RGVO SnO x nanolayers, including nonstoichiometry, presence of carbon contamination and surface bondings, the X-ray photoelectron spectroscopy (XPS) method was applied. The SnO x RGVO samples reveal nonstoichiometry because the relative concentration [O]/[Sn] equals 0.94 for the as deposited sample and increases upon subsequent air exposure and NO 2 sensing. Moreover, carbon contamination has been recognized after exposing the RGVO SnO x nanolayers to the air and during the NO 2 detection.Keywords: NO 2 surface photovoltage gas sensor; RGVO SnO x nanolayers; room temperature detection limit at ppb level