Gas sensing properties of nanostructured tin zinc oxide thin films

Abstract

In the present world of industrialization, because of the production of harmful gases as a by-product of the factories and automobiles, sensors are essentially required in all aspects of life. In many industries, various harmful, toxic and explosive gases including H2, CH4, NOX, NH3, SOX etc. have become increasingly important as raw materials. In case of accidental leakage these gases can be life threatening also and hence it has become very important to develop highly sensitive gas sensors. Gas sensors based on semiconducting metal oxides have gained a lot of interest in last few decades. However, some unresolved issues that require special attention include the realization of gas sensors with low operating temperature, higher response towards low concentration of target gas, fast response and recovery speeds, low power consumption, low cost etc. Hydrogen is a colorless, odorless, explosive, and extremely flammable gas having low minimum ignition energy (0.017 mJ), high heat of combustion (142 kJ/g H2) and wide flammable range (4and#8722;75%), as well as a high burning velocity and detonation sensitivity. Hydrogen is envisioned as the most attractive basic and sustainable energy source for the future generation due to its high efficiency and renewable properties. Hydrogen gas is important in the synthesis of ammonia and methanol, the hydration of hydrocarbons, the desulphurization of petroleum products and the production of rocket fuels, in metallurgical processes etc. However, leakage of H2 may lead to some fatal accidents which can be prevented if detected timely. To monitor such leakages, the development of sensors with improved sensitivity and selectivity is essentially required. Recently, metal oxide semiconductor thin films have attracted considerable interest as gas sensing materials due to their higher specific surface area and smaller grain size than bulk materials, which can lead to higher response, lower operating temperatures and fast response processes. Moreover, nanocrystalline thin films are more compat