W/Mo/Cr Doping\nModulates the Negative–Positive\nInversion Gas Sensing Behavior of VO<sub>2</sub>(M1)

The anomalous gas sensing behavior has garnered significant\nattention\nfrom researchers, prompting a re-evaluation of the gas sensing theory.\nThis work focuses on inversion gas sensing behavior induced by element\ndoping. W/Mo/Cr-doped VO<sub>2</sub>(M1) samples are synthesized,\nand their sensing behaviors are investigated. The results show that\nthe elements can modulate the sensing behavior with an opposite orientation.\nThe sensing behavior in the opposite orientation is attributed to\nthe extent of the reduced Fermi level of VO<sub>2</sub>(M1) after\ndoping. W-doped VO<sub>2</sub>(M1) maintains a resistance-decreased\nsensing behavior (-n). In contrast, the decrease in Fermi level results\nin the formation of a Schottky barrier between the gas-absorbed Mo/Cr-doped\nVO<sub>2</sub>(M1) and the electrode. The formation of Schottky barriers\nleads to the inversion sensing behavior, which feedbacks as an increased\nresistance (-p). This study offers a novel perspective on the gas\nsensing theory.