In this work, we develop a gate-tunable gas sensor based on a MoS2/hBN heterostructure field effect transistor. Through experimental measurements and numerical simulations, we systematically reveal a principle that relates the concentration of the target gas and sensing signals (ΔI/I 0) as a function of gate bias. Because a linear relationship between ΔI/I 0 and the gas concentration guarantees reliable sensor operation, the optimal gate bias condition for linearity was investigated. Taking NO2 and NH3 as target molecules, it is clarified that the bias condition greatly depends on the electron accepting/donating nature of the gas. The effects of the bandgap and polarity of the transition metal dichalcogenides (TMDC) channel are also discussed. In order to achieve linearly increasing signals that are stable with respect to the gas concentration, a sufficiently large V BG within V BG > 0 is required. We expect this work will shed light on a way to precisely design reliable semiconducting gas sensors based on the characteristics of TMDC and target gas molecules.

Unintentional bubbles are formed when manufacturing devices using two-dimensional materials. Usually, these bubbles affect device performance degradation, but in the case of memory devices, an additional charge trap can be expected. We investigate the direct surface potential of bubbles formed in a hexagonal boron nitride (hBN)/multilayer graphene (MLG) heterostructure. Specifically, we study the electron transfer improvement by increasing the memory window of a MoS 2 /hBN/MLG heterostructure in floating gate memory owing to bubbles formed at the hBN/MLG heterointerface. This characterization of bubbles containing molecules such as water or hydrocarbon in two-dimensional material heterointerfaces can promote the understanding of charge carrier tunneling in two-dimensional material heterostructures.

Hot electron photodetection provides a powerful platform for photosensing beyond the bandgap of a semiconductor. High‐performing hot electron photodetection has been reported in 2D transition metal dichalcogenide material‐based devices without the support of plasmonic metal nanostructures but with planar metal electrodes. However, the mechanism driving hot electron dynamics in 2D transition metal dichalcogenide devices has not been explored. Here, we uncover the hot electron transfer in MoS2 and Pt van der Waals (vdW) metal electrodes by transient reflection spectroscopy, revealing a sub‐picosecond transfer time of hot electron and a decelerated recombination process in MoS2 at the below bandgap photoexcitation compared to the pristine MoS2. With an independent photocurrent mapping, the ultralong diffusion is revealed in MoS2/vdW metal electrode and a self‐powered near‐infrared (NIR) photodetector is demonstrated with a high responsivity of 6 mA W−1 and detectivity of 9 × 109 Jones at a wavelength of 1062 nm by integrating Pt and Ag asymmetric vdW electrodes into MoS2. The results will pave the way for the next generation of hot‐electron‐based self‐powered optoelectronic devices.

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