Integrated graphene - based sensor devices via scalable microfabrication process development based on graphene - metal multilayer deposition

尽管石墨烯具有挑战性的性质，但将石墨烯用于技术应用仍然需要在开发专用加工方法方面做出相当大的努力，这些方法具有适应并最终用于工业规模器件制造的潜力。在迄今为止已经研究的工艺中，在铜上化学气相沉积石墨烯，其中铜作为催化剂促进单层石墨烯的生长-似乎是最有前途的方法之一。尽管进行了广泛的研究，但该工艺存在与质量、再现性和产率相关的问题，这些问题与铜和石墨烯之间的界面缺乏控制有关。在该过程中，我们将能够通过组合的原位沉积系统以更可控的方式解决这些问题，其中铜和其他可能的金属与石墨烯CVD一起沉积在一个真空系统内，即不将样品暴露于周围环境。与2D Ga-Al-As半导体异质结构一样，通过原位多层沉积工艺在原子长度尺度上控制界面有望成为在可制造器件结构中利用石墨烯独特特性的途径。尽管有这种潜力，我们认为石墨烯完全集成到CMOS技术中，尽管从长远来看是极具挑战性的，但仍然有很长的路要走，并且如果没有根本不同的处理方法，甚至可能是不可能的。然而，传感器技术作为一个整体大多基于混合解决方案，其中传感器本身-甚至在某些情况下基于芯片-仍然通过倒装芯片、引线键合或简单的传统布线与CMOS数字电子器件分离。一个广泛使用的高工业影响的例子是压电传感器，其中锆钛酸铅陶瓷的高加工温度与CMOS加工条件不相容。基于这一理念，我们相信，金属-石墨烯多层膜的原位生长方法，正如本项目所设想的那样，将使得能够显著改进现有的传感器概念以及实现和制造新的传感器概念。基于我们在帝国理工学院和NPL的科学合作伙伴以及我们来自行业的相关合作伙伴的专业知识，我们将专注于生物传感器应用，其中石墨烯作为碳基材料作为生物界面特别具有挑战性。作为-从工艺技术的角度来看-最简单的方法，石墨烯涂覆的铜电极将具有用于射频-微波-太赫兹生物传感器的潜力，其中铜将由于较低的传导损耗而优于金，并且石墨烯提供了生物分子和细胞的界面。作为工艺技术复杂性增加的第二步，我们认为用于任意形状的独立式石墨烯膜和（亚）微米级弯曲梁的牺牲层工艺是现实的发展目标。这项技术将使纳米机械传感器阵列的发展，基于石墨烯的特殊机械性能。除了传感器应用之外，石墨烯基NEMS结构也是纳米技术和生物学计量学的改进和探索的挑战性对象，这是我们NPL的合作者所追求的。最近发现的受限等离子体激元-极化激元激发-源于石墨烯独特的电子性质-是目前石墨烯研究界最热门的话题之一。我们相信，我们将能够用这种沉积套件制造定制的独立结构，将为探索并最终利用石墨烯的这种独特的光学-红外特性用于新型传感器应用铺平道路。

In spite of its challenging properties, the utilization of graphene for technical applications still demands considerable efforts in developing dedicated processing methods, which have a potential to be adapted and finally utilized for industrial scale device manufacturing. Among the processes which have been investigated so far, chemical vapour deposition of graphene on copper, where copper acts as a catalyst to facilitate the growth of single layered graphene - appears to be one the most promising approaches. Although extensively studied, there are issues with this process related to quality, reproducibility and yield, which are connected to the lack of control of the interface between copper and graphene. Within the process, which we will be able to tackle these issues in a more controllable way by a combined in-situ deposition system, where copper and other possible metals are deposited within one vacuum system together with the graphene CVD, i.e without exposing the sample to an ambient environment. Like for 2D Ga-Al-As semiconductor heterostructures, the control of the interfaces on an atomic length scale by means of an in-situ multilayer deposition process is expected to be the pathway which will enable the ultilization of graphene's unqiue properties within manufacturable device structures.In spite of this potential, we feel the full integration of graphene into CMOS technology, although being extremely challenging on the long term - still has a very long way to go and may even be impossible without fundamentally different processing approaches. However, sensor technologies as a whole are mostly based on hybrid solutions, where the sensor itself - even chip based in some cases - is still separated from the CMOS digital electronic by flip chip, wire bonding or simple by conventional wiring. A widely used example of high indutrial impact are piezoelectric sensors, where the high processing temperature of the lead-zirconium-titanate ceramics are incompatible with CMOS processing conditions.Based on this philosophy, we believe that the in-situ growing approach for metal-graphene multilayers, as envisaged to be developed within this project, will enable a significant improvement of existing sensor concepts and the realization and manufacturing of new sensor concepts. Based on the expertise of our scientific partners within Imperial College and NPL and our associated partners from industry, we will focus on biosensor applications, where graphene - as carbon based material - is particularly challenging as bio-interface. As - from the point of view of process technology -the most simple approach, graphene coated copper electrodes will have a potential for radiofrequency - microwave - terahertz biosensor, where copper will outperform gold due to lower conduction losses and graphene provides the interface to the biomolecules and cells. As a second step on a scale of increasing complexity of process technology, we believe that a sacrificial layer process for arbitrary shaped free standing graphene membranes and (sub)micro scale flexural beam is a realistic development goal. This technology will enable the development of arrays of nanomechanical sensors, based on the exceptional mechanical properties of graphene. Apart from sensor applications, graphene- based NEMS structures are challenging objects for the refinement and exploration of metrology for nanotechnology and biology, as being pursued by our collaborators from NPL.The recently discovered confined plasmon-polariton excitations - originating from the unique electronic properties of graphene - are currently one of the hottest topic within the graphene research community. We believe, that the tailored free standing structures we will be able to manufacture with this deposition kit, will pave the way to explore and finally utilize this unique optical - infrared properties of graphene for novel sensor applications.