Two-dimensional materials (2DMs) have been widely studied as sensing materials because their distinct 2D structure allows their entire volume to adsorb gas molecules. Black phosphorus (BP) has received much attention in recent years as one of the promising 2DMs. BP has direct band gap (0.3-2.0 eV), high carrier mobility (~1,000 cm²/V∙s) and high current on/off ratio (10⁴-10⁵). In addition, the unique properties of BP such as puckered structure, lone pair electrons on the surface and high charge transfer rate results in high sensitivity toward gas molecules. It is reported that BP shows higher sensitivity compared to graphene and MoS₂. However, the sensitivity of BP-based gas sensor still requires better performance for the practical use.

In our study, we have tried to enhance the sensing properties of BP-based gas sensors toward NO₂, NH₃, and H₂. BP-based gas sensors were fabricated by using a dry-transfer technique. BP flakes mechanically exfoliated from the bulk sample were transferred on to source-drain electrodes; the electrodes (Ti/Au) were pre-patterned on a SiO₂/Si substrate. We performed two different approaches to improve the sensitivity of the sensors. First, we altered the supported structure to suspended structure to use both sides as the sensing area and eliminate the substrate effect such as charge scattering. We also functionalized BP sensors with Pt nanoparticles to improve its hydrogen sensing ability. We measured the resistive sensitivity and confirmed that sensing performance of treated sensors was higher than that of the untreated samples. The details of our experiment conditions and results will be presented at the meeting.