Artificially Designed 2D Composite Material With Tailored Thermal Expansion Toward Temperature-Stable and Accurate Nanomechanical Pressure Sensors.

Two-dimensional (2D) materials are suitable for constructing resonant nanoelectromechanical systems (NEMS) toward advanced sensing applications, due to their ultrasmall mass, high Young's modulus, and large strain limit. However, there exists a fundamental limitation: the thermal expansion of 2D materials leads to intrinsic frequency susceptibility of 2D NEMS to temperature variation, which has significantly impaired their deployment in realistic sensing applications. Here, leveraging the layer degree of freedom in 2D materials, we realize a type of artificially designed 2D composite materials, in this case specifically designed graphene-molybdenum disulfide (MoS2) van der Waals heterostructures, with tailored thermal expansion, and successfully suppress temperature-induced frequency drift by leveraging the near-zero net thermal expansion. With this approach, we demonstrate temperature-stable and highly-accurate NEMS pressure sensors: within 200-400 K range, we improve the temperature stability by 2-orders-of-magnitude compared with individual MoS2 and graphene devices, and achieve nearly 2000-fold enhancement of signal-to-error ratio over the entire temperature range required for automotive grade sensors. Our strategy offers an effective solution, with clear design guideline, for tailoring the thermal expansion of 2D materials, opening new possibilities in temperature-stable 2D NEMS sensing applications under realistic environmental settings.