In-situ Mass and Elasticity Monitoring of Emerging Materials at High Temperature

由于我们在纳米尺度上表征新兴材料的能力不断提高，半导体工业已经成功地向更小尺寸的器件迈进。高度复杂、昂贵和标准的表征工具，如扫描电子显微镜（SEM）、扫描隧道显微镜（STM）、透射电子显微镜（TEM）和原子力显微镜（AFM），通常在非原位（材料生长/沉积后）使用，并在接近环境温度的条件下操作。扩大新兴材料应用规模的关键障碍之一是在加工过程中进行原位表征并提供对材料性能的实时控制。对于在极高温度（900 K以上）下沉积/生长的材料，原位材料表征变得更具挑战性。其中一个例子是在1200 K的温度下对过渡金属上使用化学气相沉积法生产的单层石墨烯薄膜进行原位重量和机械测量。现有的方法不足以在高温下工作，并且通常依赖于人工将生长后的石墨烯薄片转移到传感器或虚拟衬底表面以进行进一步分析。手工转移过程容易造成表面污染和材料特性的改变，从而影响样品的完整性。因此，迫切需要对材料进行原位表征，以确保可靠性，适合特定应用，从而在新兴纳米材料（包括二维材料）的薄膜生长过程中提供更好的控制。目前面临的挑战是要超越现有昂贵的方法，提供一种强大、低成本、易于集成的实时监测解决方案，类似于具有高温操作能力的石英厚度监测。在提出的工作中，我们将探索使用微机械双桨振荡器几何形状作为原位质量和弹性监测传感器。这项工作还将探索物理（使用有限元方法）背后解耦质量和弹性测量使用振荡器的特殊扭转共振模式。

The semiconductor industry has successfully moved towards smaller-scale devices due to continuous improvements in our ability to characterize emerging materials at the nanoscale. Highly sophisticated, expensive and standard characterization tools like scanning electron microscopy (SEM), scanning tunnelling microscopy (STM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) are typically used ex-situ (after material growth/deposition) and operate close to ambient temperature. One of the key barriers to up scaling the applications of new/emerging materials is to perform in-situ characterization and provide real-time control over material properties during processing. The in-situ material characterization becomes more challenging for materials deposited/grown at extremely high temperatures (above 900 K). One such example is performing in-situ gravimetric and mechanical measurements on monolayer graphene films produced using chemical vapour deposition on transition metals at 1200 K. The existing methods are not sufficient to operate under high temperatures and typically depend on manual transfer of graphene flakes after growth to the surface of sensor or dummy substrates for further analysis. The manual transfer process is prone to surface contamination and changes to material properties, thus compromising sample integrity. Therefore, there is an imminent need for in-situ material characterization to ensure reliability, suitability for a particular application and in turn provide better control during thin film growth of emerging nanomaterials (including 2D materials).The challenge is to look beyond the existing expensive methods and provide a robust, low-cost, easy-to-integrate, and real-time monitoring solution similar to a quartz based thickness monitoring with high temperature operation capabilities. In the proposed work, we will explore the use of a micro-machined double paddle oscillator geometry as in-situ mass and elasticity monitoring sensor. This work will also explore physics (using finite element methods) behind decoupling mass and elastic measurements using a special torsional resonance mode of the oscillator.