Sensitive, selective and stable tin dioxide thin-films for carbon monoxideand hydrogen sensing in integrated gas sensor array applications

This paper reports on the preparation, electrical and surface characterizat ion of Cu doped tin dioxide thin-films for highly selective integrated gas sensor devices. The 3000 Angstrom thin-film of 0.16 wt.% copper doped tin d ioxide was deposited by reactive R.F. sputtering at room temperature and fo llowed by 10 Angstrom Pt on top of Cu doped tin dioxide thin-film (SnO2-Cu/ Pt). In another batch, the 100 Angstrom SiO2 thin-film was deposited on top of the SnO2-Cu/Pt thin-film structure (SnO2-Cu/Pt/SiO2). The electrical re sponse of these thin-films was investigated for CO and H-2 gases at differe nt temperatures and gas concentrations. The device with the SnO2-Cu/Pt thin -film, showed excellent electrical response towards CO gas and device with SnO2-Cu/Pt/SiO2 thin-film showed response towards hydrogen only. The SiO2 t hin-film prevents the diffusion of CO gas and only hydrogen gas diffuse thr ough silicon dioxide layer. Using thin-films structure SnO2-Cu/Pt and SnO2- Cu/Pt/SiO2, a highly selective sensor device for CO and H-2 gas was fabrica ted. The surface characterization of these thin-films was performed using s canning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS ) techniques. The SEM picture showed that surface structure of the SnO2 thi n-film improved by copper doping. (C) 2001 Elsevier Science B.V. All rights reserved.