Highly sensitive and multidimensional detection of NO 2 using In 2O 3 thin films

Abstract

We report on the ultrasensitive and unique detection of NO 2 with respect to common gaseous interferents through multi-dimensional signature analysis using In 2O 3 thin films as sensing layers. Sensor devices fabricated using interdigitated metal fingers of Ti/Au deposited on the In 2O 3 film resulted in extremely high sensitivity for NO 2 molecules, producing 20% change in conductance for 20 ppb NO 2 in atmospheric conditions. Molecular adsorption induced changes in conductance (G), capacitance (C), and surface work function ( ϕ) upon exposure to various gases were measured to obtain their respective C– G and ϕ– G plots. We observed that the gradients of the ( C– G) and ( ϕ– G) plots are distinct for individual analytes and can thus can be utilized for the specific detection of molecules. Three dimensional G– C– ϕ signature plots for NO 2 and NH 3 were found to be even more effective than 2D plots in uniquely identifying the gases. Utilization of 2D signatures to analyze a binary gas mixture was found to be quite promising with a large application potential.