Department of Electrical Engineering, University of South Carolina, Columbia, SC, 29208, USA.
Small. 2014 Apr 24;10(8):1555-65. doi: 10.1002/smll.201302818. Epub 2013 Dec 23.
A new chemical sensor based on reverse-biased graphene/Si heterojunction diode has been developed that exhibits extremely high bias-dependent molecular detection sensitivity and low operating power. The device takes advantage of graphene's atomically thin nature, which enables molecular adsorption on its surface to directly alter graphene/Si interface barrier height, thus affecting the junction current exponentially when operated in reverse bias and resulting in ultrahigh sensitivity. By operating the device in reverse bias, the work function of graphene, and hence the barrier height at the graphene/Si heterointerface, can be controlled by the bias magnitude, leading to a wide tunability of the molecular detection sensitivity. Such sensitivity control is also possible by carefully selecting the graphene/Si heterojunction Schottky barrier height. Compared to a conventional graphene amperometric sensor fabricated on the same chip, the proposed sensor demonstrated 13 times higher sensitivity for NO₂ and 3 times higher for NH₃ in ambient conditions, while consuming ∼500 times less power for same magnitude of applied voltage bias. The sensing mechanism based on heterojunction Schottky barrier height change has been confirmed using capacitance-voltage measurements.
一种基于反向偏置石墨烯/硅异质结二极管的新型化学传感器已经被开发出来，该传感器具有极高的偏置依赖性分子检测灵敏度和低工作功率。该器件利用了石墨烯的原子级薄特性，使得分子可以吸附在其表面，直接改变石墨烯/硅界面势垒高度，从而在反向偏置下对结电流产生指数级影响，从而实现超高灵敏度。通过在反向偏置下操作该器件，可以通过偏置幅度来控制石墨烯的功函数，从而控制石墨烯/硅异质结势垒高度，从而实现分子检测灵敏度的广泛可调性。通过仔细选择石墨烯/硅异质结肖特基势垒高度，也可以实现这种灵敏度控制。与在同一芯片上制造的传统石墨烯安培传感器相比，所提出的传感器在环境条件下对 NO₂的灵敏度提高了 13 倍，对 NH₃的灵敏度提高了 3 倍，而消耗的功率却降低了约 500 倍。使用电容-电压测量证实了基于异质结肖特基势垒高度变化的传感机制。
