Abstract
Highly sensitive and energy-efficient gas sensors are essential for real-time environmental monitoring and air quality assessment. In this work, we present an optically programmable gas sensor based on WSe2/hBN heterostructure transistors for NOx detection. The hBN interfacial layer enhances device performance by reducing charge trapping and improving transport, enabling the WSe2/hBN configuration to achieve a higher sensing response and faster recovery than WSe2/SiO2 devices. To understand the sensing mechanism, in situ Kelvin probe force microscopy (KPFM) was used, revealing that NOx adsorption at the metal/semiconductor interface modulates the Schottky barrier height (SBH), which governs charge transport and gas sensitivity. Furthermore, we demonstrate that UV-induced charge modulation allows dynamic control of the sensor response, offering a tunable and reversible method for optimizing gas detection. This study highlights the potential of heterostructure engineering and optoelectronic modulation in developing next-generation, low-power, smart gas sensors for environmental monitoring applications.