Van der Waals (vdW) heterostructures with 2D materials have shown that atomically thin non‐volatile memories are advantageous in terms of integration, while offering high performance and excellent stability. The non‐volatile memory behavior of 2D materials has mainly been studied for single‐bit operation, and there is growing interest in expanding to multi‐bit operation to enhance the storage capacities of memory devices. However, the conditions or rules for generating the desired number of bits in 2D‐based multi‐bit memory remain to be identified. In this study, multiple bits are successfully created on non‐volatile memory based on vdW heterostructure floating‐gate memory (FGM) by systematically tuning the dimensions of the 2D materials. In particular, a fingerprint mechanism is established that links the bit number and dimensions of 2D crystals on vdW heterostructures. This approach could enable the precise generation of the desired number of bits in layered‐material‐based vdW FGMs.

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.

In this work, oxidized black phosphorus (BP) was trapped in the top and bottom interfaces of graphite thin film electrodes by hexagonal boron nitride (hBN) encapsulation. Upon using partial encapsulation of hBN on BP, the oxidation of bare BP area led to the oxidation of hBN encapsulated whole BP, and this oxidized BP could be confined in the hBN layer. Furthermore, by attaching graphite thin film electrodes on and underneath the oxidized BP layer, charge carrier injection and extraction behavior from measuring the current tunneling was characterized by applying a bias voltage between the top and the bottom graphite thin film electrodes. The electrical characteristics according to applied bias voltage was confirmed with a double log plot. It was found that the ohmic current region exists in the low voltage state, and the space-chargelimited conduction region exists in the high voltage state.

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.

On applying partial gate voltages, we were able to perceive precise and minute conductance variations for the entire graphene electrode, arising mainly from different sub-micrometer scale widths of the graphene ribbons (GRs), which could not be distinguished using conventional global gating methods.

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