Suspended black phosphorus nanosheet gas sensors

The studies on enhancing the sensitivities of chemical sensors based on two-dimensional (2D) materials have been focused primarily on surface modifications including defect engineering, chemical doping, and incorporation of metal nanoparticles. Exfoliated black phosphorus (BP), which is one of the 2D materials, has attracted considerable attention because it offers higher sensitivity than other 2D materials (e.g., graphene and MoS₂). In this study, for the first time, we attempt to increase the performance of BP chemical sensors to their theoretical limit by floating BP flakes on top of electrode posts in order to provide full (both sides) adsorption sites and avoid interface scattering effects. Our suspended BP gas sensors fabricated via dry transfer showed higher sensing performances than the conventional supported BP gas sensors (gas response was increased by approximately 23% at 200 ppm). In addition, faster response and recovery with high reproducibility were observed in suspended BP chemicals sensors than in the supported ones. Our work reveals the full potential of pristine BP-based chemical sensors and paves the way for the next-generation high performance 2D chemical sensors.