<span style="font-size: 22.5pt;mso-bidi-font-size:15.5pt;font-family:"Times New Roman","serif"; mso-bidi-font-weight:bold">Effect of preparation procedures on long-term performance of SnO_{<span style="font-size:17.5pt;mso-bidi-font-size:10.5pt; font-family:"Times New Roman","serif";mso-bidi-font-weight:bold">2</span>}<span style="font-size:17.5pt;mso-bidi-font-size:10.5pt;font-family:"Times New Roman","serif"; mso-bidi-font-weight:bold"> <span style="font-size:22.5pt;mso-bidi-font-size: 15.5pt;font-family:"Times New Roman","serif";mso-bidi-font-weight:bold">thin film sensing layers deposited with different methodologies </span></span></span>

749-766<span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">There is an increasing demand for SnO<span style="font-size:12.5pt; mso-bidi-font-size:5.5pt;font-family:" arial","sans-serif""="">2 semiconducting gas sensors for several monitoring applications that have sensitivity, selectivity and reliability on a long-term scale. The present paper reviews the long-term performance of SnO2 thin film sensing layers, which strongly depend on the preparation procedures and different thin film deposition techniques. <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">The stability and reliability are very important for tin dioxide based gas sensor devices, when these are to be integrated with standard CMOS circuitry. The stability in the output of the thin film sensing layer is very essential to implement reliable integrated sensor device, because a small drift in the baseline leads to a large change in the biasing current in the subsequent <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">signal processing circuit. The long-term stable behaviour of the SnO2 thin film gas sensor has been found in the literature, and it depends on the thin film deposition conditions, annealing temperature, time, ambient, and noble metal/metal oxide dopant. It can be seen from the literature that, sensitivity and stability of SnO<span style="font-size:13.0pt;mso-bidi-font-size: 6.0pt;font-family:" times="" new="" roman","serif""="">2 thin film were strongly affected with variation in the crystallite (grain) size and growth procedures. The thin films were deposited by chemical methods such as, screen-printing, sol-gel, spray pyrolysis, etc. and physical methods such as, RGTO, sputtering, PLA, etc. with the grain size varying from 5 to 50 nm with annealing temperatures varying in the range 500-800<span style="font-size:20.0pt; mso-bidi-font-size:13.0pt;font-family:" times="" new="" roman","serif""="">°C and with noble metal/metal oxide dopants. Such type treated SnO2 thin films have a little change in sensitivity but the sensing layer has much higher, long time operational stability. </span