RESUMEN
Atomically thin two-dimensional (2D) semiconductors are promising for next-generation memory to meet the scaling down of semiconductor industry. However, the controllability of carrier trapping status, which is the key figure of merit for memory devices, still halts the application of 2D semiconductor-based memory. Here, we introduce a scheme for 2D material based memory using wrinkles in monolayer 2D semiconductors as controllable carrier trapping centers. Memory devices based on wrinkled monolayer MoS2 show multilevel storage capability, an on/off ratio of 106, and a retention time of >104 s, as well as tunable linear and exponential behaviors at the stimulation of different gate voltages. We also reveal an interesting wrinkle-based carrier trapping mechanism by using conductive atomic force microscopy. This work offers a configuration to control carriers in ultrathin memory devices and for in-memory calculations.
RESUMEN
Two dimensional transition metal dichalcogenides (TMDCs) have attracted much interest and shown promise in many applications. However, it is challenging to obtain uniform TMDCs with clean surfaces, because of the difficulties in controlling the way the reactants are supplied to the reaction in the current chemical vapor deposition growth process. Here, we report a new growth approach called 'dissolution-precipitation' (DP) growth, where the metal sources are sealed inside glass substrates to control their feeding to the reaction. Noteworthy, the diffusion of metal source inside glass to its surface provides a uniform metal source on the glass surface, and restricts the TMDC growth to only a surface reaction while eliminating unwanted gas-phase reaction. This feature gives rise to highly uniform monolayer TMDCs with a clean surface on centimeter-scale substrates. The DP growth works well for a large variety of TMDCs and their alloys, providing a solid foundation for the controlled growth of clean TMDCs by the fine control of the metal source.
RESUMEN
Doping is an effective way to modify the electronic property of two-dimensional (2D) materials and endow them with additional functionalities. However, wide-range control of the doping concentrations in monolayer 2D materials with large-scale uniformity remains challenging. Here, we report in situ chemical vapor deposition growth of vanadium-doped monolayer molybdenum disulfide (MoS2) with widely tunable doping concentrations ranging from 0.3 to 13.1 atom %. The key to regulate the doping concentration lies in the use of appropriate vanadium precursors with different doping abilities, which also generate large-scale uniform doping to MoS2. Artificial synaptic transistors were fabricated using the heavily doped MoS2 as the channel material. Synaptic potentiation, depression, and repetitive learning processes were mimicked by the gate-tunable changes of channel conductance in such transistors with abundant vanadium atoms to trap/detrap electrons. This work develops a feasible method to dope monolayer 2D semiconductors and demonstrates their applications in artificial synaptic transistors.