Novel Selectivity: Target of Gas Sensing Defined by Behavior

Traditional selectivity of gas sensors determined by the magnitude of the response value has significant limitations. The distinctive inversion sensing behavior not only defies the traditional sensing theory but also provides insight into defining selectivity. Herein, the novel definition of selectivity is established in a study with VO₂(M1). The sensing behavior of VO₂(M1) is investigated after its synthesis conditions optimization by machine learning. In gases of the same nature, VO₂(M1) shows remarkably selective for NH₃ marked with unique resistance increase behavior. Such anomalous behavior is attributed to the formation of the Schottky junction between VO₂(M1) and the electrode. The "work function-electron affinity" relation is summarized as the selectivity coefficient, a parameter for predicting the selectivity of the sensing material effectively.