DEVELOPMENT OF HIGH-SENSITIVITY TIN OXIDE-BASED SENSORS FOR GAS ODOURDETECTION AT ROOM-TEMPERATURE/

An effort has been made to develop thick film tin oxide gas sensors wh ich could detect various gases/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for variou s durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the se nsitivity of the non-annealed sensors. Further, plasma annealed sensor s are found to be practically independent of temperature and the room temperature sensitivity of these sensors are found to be about 1.5 tim es the sensitivity of the conventional sensors at its operating temper ature of 300 degrees C. Studies on the variation of d.c. resistance, s ensitivity, temporal response, current-temperature characteristics and impedance spectroscopy with the annealing time have also been made. T hese studies reveal that, with the increase in annealing time, there i s a permanent gradual reduction in the d.c. resistance of annealed sen sors. Further, it is also observed that with the increase in annealing time, the response time improves, barrier height reduces, barrier cap acitance increases and the dependence of the sensitivity with temperat ure reduces while the sensitivity itself improves many-fold. (C) 1998 Elsevier Science S.A. All rights reserved.