One-Step Van der Waals Integration of Multi-Threshold 2D Functional Circuits

Transition-metal dichalcogenides (TMDs), as atomically thin semiconductors, have shown immense promise for next-generation electronics due to their high mobility and potential for creating van der Waals heterostructures. However, precise control of the threshold voltage (V_th) in field-effect transistors (FETs) remains a significant challenge, impeding the development of 2D material circuits with tailored electronic functions. Herein, a graphene-assisted one-step van der Waals integration technique is presented for fabricating multi-threshold 2D functional circuits. Graphene's unique property of having a surface without dangling bonds is utilized as an intermediary layer, allowing for the transfer of electrodes with various work functions and high-κ dielectric layers onto 2D channel materials in a single step. This technique has successfully produced Al-gated MoS₂ FETs with a V_th of −0.2 V and Au-gated MoS₂ FETs with a V_th of 1.9 V. This precision enables the development of functional devices such as rail-to-rail inverters with large noise margins. Furthermore, more complex multi-threshold 2D circuits are achieved, including basic logic gates (NOT, NAND, NOR), six-transistor static random-access memory (6T-SRAM), and ring oscillators (RO). This work showcases a scalable and effective strategy for threshold voltage engineering in 2D material-based circuits, paving the way for sophisticated electronic and optoelectronic applications.