Elucidating iron doping induced n- to p- characteristics of Strontium titanate based ethanol sensors

• Published in: Current applied physics Vol. 18; no. 2; pp. 246 - 253
• Main Authors: Sarin, Neha, Mishra, Monu, Gupta, Govind, Parkin, Ivan P., Luthra, Vandna
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2018; 한국물리학회
• Subjects: Doping; Ethanol sensing; n- and p-type gas sensors; Strontium titanate; XPS; 물리학; Strontium titanate; XPS; Ethanol sensing; Doping; n- and p-type gas sensors
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2017.11.007

A series of pure and iron doped strontium titanate, (SrFexTi1-xO3; x = 0, 0.1 and 0.2) powders were synthesized, characterized and used to fabricate ethanol sensors for low concentration. X-Ray Diffraction (XRD) technique was used to confirm the single phase formation. Microstructural properties of the powders were investigated using scanning electron microscopy (SEM). Electrical conductivity of all the samples at room temperature (RT) was measured. Sensors were optimized for best responsiveness by varying the operating temperature from 350 °C to 500 °C.The sensor with doping x = 0.2 exhibited best sensing response at 400 °C for ethanol gas. The undoped sensor demonstrated a decrease in resistance on exposure to ethanol gas whereas Fe-doped sensors showed increase in resistance. The doping induced changeover from n to p behavior in the sensing response on doping has been investigated and corroborated with an observed shift in the Fermi level position by X-ray photoelectron spectroscopy (XPS). The disparity in gas sensing response clearly demonstrates inter-connection of multiple influencing factors such as electrical conductivity, morphology, porosity and change in chemical composition on doping. The sensors were exposed to ethanol, nitrogen dioxide, carbon monoxide, butane gases at concentration between 5 ppm and 50 ppm. The sensor exhibited much reduced relative response to all gases other than ethanol which can be utilized for wide range of applications. •Electrical and structural properties of pure and Fe-doped SrTiO3 were probed by dc conductivity, XRD and SEM studies.•The gas sensing behavior was tested for ethanol (5–50 ppm). Optimum gas sensing response was observed for 20% Fe-doping.•Sensors demonstrated least cross-sensitivity for reducing and oxidizing gases.•Substitution of Ti4+ by Fe3+ leads to changeover from n to p type in sensing response. It was unpinned by VB shift in XPS.