The electronic nose (e-nose), one of the electronic sensor systems, is an analysis system composed of arrays of chemical sensors to mimic the mammalian olfactory system that recognizes different odors. The e-nose analyzed many odor components quickly, analyzing individual odor components and simultaneously detecting patterns of overall odor components. Metal oxide semiconductors (MOS), a chemo-resistive material that changes its electrical resistance in response to changes in the nearby atmosphere, are a great candidate for the building block of the e-nose system due to their high sensitivity, low cost, and simplicity. Also, the low selectivity issue of MOS can be supplemented with the assembly of sensors to be a cross-reactive sensor array.
Herein, we suggested the metal oxide array with high compositional tunability by laser-induced oxidation. When the laser beam irradiates the metallic film, oxidation occurs depending on the amount of light due to the interaction between oxygen and materials. As a result, various metal oxide layers with the controlled composition of oxygen are fabricated and operated differently because of their oxygen nonstoichiometry. To verify the laser-induced oxidation, we analyze the composition of metal oxide films by Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Also, we measured the sensing behaviors of the laser-oxidized MOS sensor array during the exposure of 8 different odor molecules (Heptanol, 2-ethylfenchol, D-limonene, Octanal, Decanal, Cis-3-hexenol, 2,3,5-trimethylpyrazine, and Geraniol) by bubbler system. And then, we classified 8 different recognized patterns by extracting the characteristics of gas sensors.

Acknowledgment

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education(2020R1A6A1A03040516). Also, this work was supported by the NRF grants (2019M3C1B8090840) funded by the Ministry of Science and ICT (MSIT).