Nitrogen doped In$_2$O$_3$-ZnO nanocomposite thin film based sensitive and selective ethanol sensor

Abstract

Nanocomposite metal oxide thin films exhibit assuring qualities in the field of gas sensors because of the collective opportunities provided by the heterointerface formation. In this work, we present the synthesis of nitrogen doped mesoporous In$_2$O$_3$-ZnO nano-composite thin films by simple wet chemical method using urea as the nitrogen precursor. SEM investigation suggests formation of mesoporous nano-composite thin films, where the uniformity of surface pore distribution depends on the relative proportion of In$_2$O$_3$ and ZnO in the composites. HRTEM investigation suggest formation of sharp interfaces between N-In$_2$O$_3$ and N-ZnO grains in the nano-composite thin films. The nano-composite thin films have been tested for their ethanol sensing performance over an extensive range of temperature, ethanol vapor concentration and relative humidity. Nitrogen doped nano-composite thin film with equal proportion of In$_2$O$_3$ and ZnO exhibits excellent ethanol sensing performance at a reasonable operating temperature (~94 % at 200 {\deg}C for 50 ppm of ethanol), fast response time (~two seconds), stability over time, enhanced resilience against humidity and selectivity to ethanol over various other volatile organic compounds.