Size-dependent gas sensing properties of indium oxide nanoparticle layers

In2O3 nanoparticle layers having an average size of 8, 11, 15, 21, and 29 nm have been deposited using a two-step method consisting of chemical capping and dip coating techniques. The gas sensing properties in terms of sensor response and response time of the nanoparticle layers towards ethanol have been studied as a function of ethanol concentration and operating temperature. It has been observed that the sensor response increases and the response time decreases with decreasing size in the size range of 5-15 nm. The increase in sensor response at smaller nanoparticle size has been explained in terms of the increase in surface area and particle size becoming comparable to the electron Debye length.