Biaxial Strained Transfer of Atomically Thin Nano-Electro-Mechanical Membranes

下一代MEMS是NEMS -纳米机电系统，并且NEMS膜的最有前途的候选者是石墨烯和二维（2-D）材料。2-D材料表现出最高性能的独特组合，例如高刚度、低弯曲模量、高弹性、低单位面积质量、低厚度和高导电性。这允许开发NEMS膜，其可以实现在传统MEMS装置和膜中通常被认为是冲突的行为，例如高谐振频率和高偏转幅度。许多2-D NEMS器件已经在实验室规模上得到了展示，包括压力、触摸和质量传感器、麦克风、自持振荡器、量子霍尔器件、RF前端滤波器、开关、光子调制器等。这些新型NEMS器件将在未来的机器人、电子、医疗保健、汽车、航空航天等领域得到应用。从实验室规模的设备到大规模制造2-D NEMS的过渡必须克服许多关键挑战。这些挑战中的一些，例如最小化纳米级缺陷和提高器件产率和性能，已经通过采用少层石墨烯或石墨烯-聚合物异质结构膜来解决。然而，在新型2-D NEMS器件的未来制造中仍然存在一个关键的突出挑战。众所周知，2-D层具有显著的内置拉伸和压缩应力，其既任意分布又难以控制。这些都是由于它们的生长方式以及它们在NEMS制造过程中从一个表面转移到另一个表面的方式引起的。在2-D NEMS器件的纳米制造中，这些内置应力在每个器件内以及在所有器件上均匀地呈现是至关重要的。这将在该项目中通过开发一种新的工艺来实现，该工艺将在从母体转移到目标NEMS基底期间向2-D膜施加良好控制的双轴拉伸应变。该应变不仅将确保悬置的膜在所有装置上是均匀的，所产生的预张力还将增加膜的刚度，并且因此增加所产生的NEMS装置的谐振品质因数。此外，通过控制预张力，可以调节装置的静态和动态灵敏度及其谐振频率。同样重要的是，实时监测所施加的应变和所得膜中的残余应变。在该项目中，我们将实施基于二维材料应变的原位应变监测，该应变可以通过其特征拉曼光谱峰值的变化来检测。该项目将使英国在晶圆级和卷对卷二维NEMS制造方面处于领先地位，建立在英国在MEMS代工厂，印刷电子，二维材料生产以及传感器和执行器方面的现有优势基础上。这反过来又将有力地加强传感器、医疗保健、通信、汽车和航空航天等其他制造业的健康。2D NEMS将使各种下一代设备和技术成为可能，这些设备和技术将使我们的社会变得更加高效、互联、健康和有弹性。

The next generation of MEMS is NEMS - nano-electro-mechanical systems, and the most promising candidate for NEMS membranes are graphene and 2-dimensional (2-D) materials. 2-D materials exhibit a unique combination of superlative properties such as high stiffness, low bending modulus, high elasticity, low mass per unit area, low thickness and high electrical conductivity. This allows for the development of NEMS membranes that can achieve behaviour that are typically considered conflicting in traditional MEMS devices and membranes, such as both high resonance frequency and high deflection amplitude. A number of 2-D NEMS devices have been demonstrated on the lab scale, including pressure, touch and mass sensors, microphones, self-sustained oscillators, quantum Hall devices, RF front-end filters, switches, photonic modulators and more. These novel NEMS devices will find applications in future robotics, electronics, healthcare, automotive, aerospace and more. The transition from lab-scale devices to large-scale manufacturing of 2-D NEMS has to overcome a number of critical challenges. Some of these challenges, such as minimising nanoscale defects and improving device yield and performance, have been addressed by employing few-layer graphene or graphene-polymer heterostructure membranes. However, there is still one key outstanding challenge in the future manufacturing of novel 2-D NEMS devices. It is well known that 2-D layers possess significant built-in tensile and compressive stresses which are both arbitrarily distributed as well as difficult to control. These arise both from the way that they are grown and the the way that they are transferred from one surface to another during NEMS manufacturing. In the nano-manufacturing of 2-D NEMS devices, it is essential that these built-in stresses are rendered uniformly within each device and across all devices. This will be accomplished in this project by developing a new process that will apply a well-controlled biaxial tensile strain to the 2-D membrane during the transfer from the parent to the target NEMS substrate. Not only will this strain ensure that the suspended membranes are uniform across all devices, the resulting pre-tension will also increase the stiffness of the membrane, and consequently the resonance quality factor of the resulting NEMS device. Furthermore, the static and dynamic sensitivity of the device and its resonance frequency can be tuned by controlling the pre-tension. It is also essential that this applied strain, and the residual strain in the resulting membrane, are monitored in real-time. In this project, we will implement in-situ strain monitoring based on the fact that the strain in 2-D materials can be detected as shifts in their signature Raman spectroscopy peaks.This project will enable the UK to take the lead in wafer-scale and roll-to-roll 2-D NEMS manufacturing, building on the UK's existing strengths in MEMS foundries, printed electronics, 2-D material production, and sensors and actuators. This in turn will strongly reinforce the health of a wide range of other manufacturing sectors including sensors, healthcare, communications, automotive and aerospace. 2-D NEMS will enable various next-generation devices and technologies that will transform our society to be more productive, connected, healthy and resilient.